Looking for Compute Games - Page 3

Ze Emulatron · 08 January 2012, 03:56

Thanks for all the effort you have put in, I have been watching the thread but just haven't had anything to add.

prowler · 09 January 2012, 23:15

That's okay, I've no right to expect any comments until I get to the part where I can actually start fixing something, and that will be very soon now.

Mapping the blocks has revealed the complete directory and file structure on the disk:

Code:

Arcade Games.info               2526 bytes
Strategy Games.info             2334 bytes
Climber 5.info                  2102 bytes
Marbles.info                    1862 bytes
Marbles                         8664 bytes
Word War.info                   2294 bytes (Broken File) Missing Block 1 (975)
Disk.info                       2214 bytes
'  .info'                       1790 bytes
Jump Ball                       6792 bytes
Biker Dave.info                 1478 bytes
Biker Dave                      6382 bytes
Jump Ball.info                  3590 bytes
Climber 5                       8915 bytes
Euchre.info                     1574 bytes
graphics.bmap                     15 bytes
Laser Chess.info                2710 bytes
Chain Reaction.info             1454 bytes
Rememory.info                   2054 bytes
The Hermit.info                  806 bytes
troybw                         22764 bytes
exec.bmap                         27 bytes
Chain Reaction                  5981 bytes
Switchbox.info                  2934 bytes
Laser Chess                    13537 bytes
Hermit.Main                    27412 bytes
dos.bmap                          34 bytes
Rememory                        5812 bytes
ReadMe                          3755 bytes
Most                           16948 bytes
Canfield                       10277 bytes
Euchre                         16620 bytes
Monte Carlo                     3101 bytes
Monte Carlo.info                2150 bytes
FileReader                     24752 bytes
Canfield.info                   2438 bytes
.info                             58 bytes
FileReader.info                 1894 bytes
IFFPuzzle                       1847 bytes
amigabasic                    103500 bytes (Broken File) Missing Blocks 1-3 (1034,1036-7)
Marbles                         1850 bytes (Broken File) Missing Block 1 (1038)
BikerDave                       2929 bytes
Monte                           2593 bytes
ChainReaction                   3577 bytes
JumpBall                        1632 bytes
files.compute                    514 bytes
WordWar                         3995 bytes
VirusKillers.info                346 bytes (Broken File) Missing Block 1 (1085)
ty                             22168 bytes
SwitchBox                       9898 bytes
LaserChess                     13286 bytes (Broken File) Missing Blocks 9-19 (253-263)
Karma                           8788 bytes
Climber5                        3628 bytes
Euchre                          5728 bytes
Rememory                        2588 bytes (Broken File) Missing Blocks 1-6 (1078-1083)
PD.pic                          7616 bytes (Broken File) Missing Blocks 13-16 (1441-1444)
V.Killers.info                   894 bytes (Broken File) Missing Block 2
 
s/
startup-sequence                 281 bytes
 
l/
 
libs/
mathtrans.library               4280 bytes
icon.library                    5896 bytes
translator.library             10592 bytes
info.library                   16372 bytes
mathieeedoubbas.library         4728 bytes
version.library                  404 bytes
diskfont.library                4900 bytes
mathieeedoubtrans.library      15620 bytes
 
devs/
serial.device                   5380 bytes
narrator.device                23280 bytes (Broken File) Missing Blocks 9-18 (21,2-10)
parallel.device                 1812 bytes
MountList                       2991 bytes
clipboard.device                6672 bytes
printer.device                 27044 bytes (Broken File) Missing Blocks 25-56 (33-43,22-32,11-20)
ramdrive.device                 2128 bytes
system-configuration             232 bytes
 
devs/keymaps/
usa0                             992 bytes
usa1                            1328 bytes
 
devs/printers/
CBM_MPS1000                     5932 bytes
generic                         1096 bytes
Xerox_4020                      6524 bytes
HP_PaintJet                     6960 bytes
HP_LaserJet                     5624 bytes
EpsonX[CBM_MPS-1250]            6824 bytes
 
devs/clipboards/
 
t/
ed-backup                        260 bytes
 
c
loadwb                          2644 bytes
endcli                           692 bytes
AddBuffers                       876 bytes
Binddrivers                     2920 bytes
SetClock                        4556 bytes
Echo                             564 bytes 
 
VirusKillers/
How-to-use-Viruscheck.doc       2771 bytes
.info                             74 bytes
How-to-use-Viruscheck.doc.info  1080 bytes
Most                           16948 bytes
Virus_Checker                  15396 bytes (Broken File) Missing Blocks 4-10 (1441-1451)
Virus_Checker.doc              24194 bytes
Virus_Checker.doc.info          1080 bytes
Virus_Checker.info             15327 bytes
 
?                               1806 bytes (Orphan File)
?                               2198 bytes (Orphan File)
?                                116 bytes (Orphan File)
?                                105 bytes (Orphan File)
?                               7698 bytes (Broken Orphan File) Missing Block 1 (969)
?                               9982 bytes (Broken Orphan File) Missing Block 1 (971)
?                               7936 bytes (Broken Orphan File) Missing Block 1 (973)
?                                662 bytes (Broken Orphan File) Missing Block 1 (977)
?                               7513 bytes (Orphan File)
?                                  6 bytes (Orphan File)
?                               5471 bytes (Broken Orphan File) Missing Block 1 (1040)
?                               5495 bytes (Broken Orphan File) Missing Block 1 (1042)
?                               6467 bytes (Broken Orphan File) Missing Block 1 (1044)
?                                 47 bytes (Orphan File)
?                               2376 bytes (Broken Orphan File) Missing Block 1 (1088)
?                                338 bytes (Orphan File)
?                                346 bytes (Orphan File)
?                               1861 bytes (Broken Orphan File) Missing Block 1
?                               5884 bytes (Broken Orphan File) Missing Blocks 1-7
?                               1861 bytes (Broken Orphan File) Missing Block 1
?                                774 bytes (Broken Orphan File) Missing Block 1
?                               1861 bytes (Orphan File)

The files are intact complete with headers except where noted.

The broken files have one or more missing blocks. Where the corresponding disk blocks can be identified, these are indicated in brackets.

The orphan files have missing file headers. This means that some disk blocks corresponding to missing data blocks cannot be identified. Some of these may not be recoverable if matching valid data cannot be found. However, not all of these files will be important.

Tomorrow, I will study the four bitmap blocks. These will tell me which files are likely to be the important ones, and then I'll construct a new bitmap, if necessary, and try to get the root block fixed so that the disk will mount as an AmigaDOS disk in Workbench.

If I get that far, I'll upload a WIP disk image, though it may have some filesystem errors caused by overwritten tracks on the original disk.

prowler · 11 January 2012, 02:07

Hey, this evening, I replaced the bad Boot Blocks with standard OFS 1.3 Boot Blocks and now the image mounts as an AmigaDOS disk in WinUAE!

However, a requester pops up twice with the message "Error validating Lazarus. Block 970 bad header type", but at least the disk image remains unmodified when ejected.

Entering list df0: ALL in a shell reveals the disk's contents, complete with time and date stamps:

Code:

Directory "df0:"
Arcade Games.info           2526 ----rwed 22-Jul-88 00:12:29
Marbles.info                1862 ----rwed 22-Jul-88 00:39:27
'  .info'                   1790 ----rwed 22-Jul-88 00:38:46
Euchre.info                 1574 ----rwed 22-Jul-88 00:37:10
Laser Chess.info            2710 ----rwed 14-Apr-87 16:44:12
Chain Reaction.info         1454 ----rwed 22-Jul-88 01:29:33
Rememory.info               2054 ----rwed 22-Jul-88 00:41:00
exec.bmap                     27 ----rwed 21-Jul-88 22:53:51
Chain Reaction              5981 ----rwed 21-Jul-88 22:53:54
Biker Dave.info             1478 ----rwed 22-Jul-88 00:38:16
Switchbox.info              2934 ----rwed 14-Apr-87 14:38:46
Hermit.Main                27412 ----rwed 21-Jul-88 22:54:07
Climber 5.info              2102 ----rwed 22-Jul-88 00:39:07
ReadMe                      3755 ----rwed 18-Nov-88 00:03:17
dos.bmap                      34 ----rwed 21-Jul-88 22:54:31
Monte Carlo                 3101 ----rwed 21-Jul-88 22:55:16
Monte Carlo.info            2150 ----rwed 22-Jul-88 00:36:19
Canfield.info               2438 ----rwed 22-Jul-88 00:37:34
Strategy Games.info         2334 ----rwed 22-Jul-88 00:14:22
IFFPuzzle                   1847 ----rwed 21-Jul-88 23:28:07
graphics.bmap                 15 ----rwed 21-Jul-88 22:53:33
amigabasic                103500 ----rwed 17-Nov-88 23:33:35
Marbles                     1850 ----rwed 29-Jun-88 12:08:50
Marbles                     8664 ----rwed 21-Jul-88 22:44:37
BikerDave                   2929 ----rwed 21-Jul-88 23:28:11
Monte                       2593 ----rwed 21-Jul-88 23:28:31
ChainReaction               3577 ----rwed 21-Jul-88 23:28:35
files.compute                514 ----rwed 07-Nov-88 09:45:16
JumpBall                    1632 ----rwed 21-Jul-88 23:28:39
The Hermit.info              806 ----rwed 21-Jul-88 21:55:44
VirusKillers.info            346 ----rwed 08-Mar-91 12:26:26
ty                         22168 ----rwed 07-Nov-88 09:49:32
.info                         58 ----rwed 14-Apr-87 14:37:40
SwitchBox                   9898 ----rwed 21-Jul-88 23:29:05
LaserChess                 13286 ----rwed 21-Jul-88 23:29:10
Karma                       8788 ----rwed 21-Jul-88 23:29:15
FileReader                 24752 ----rwed 14-Apr-87 13:43:40
Euchre                      5728 ----rwed 16-Jul-88 20:12:20
Euchre                     16620 ----rwed 21-Jul-88 22:55:12
Rememory                    2588 ----rwed 21-Jul-88 23:29:25
Rememory                    5812 ----rwed 21-Jul-88 22:54:34
Rememory                    2588 ----rwed 21-Jul-88 23:29:25
Rememory                    5812 ----rwed 21-Jul-88 22:54:34
Rememory                    2588 ----rwed 21-Jul-88 23:29:25
Rememory                    5812 ----rwed 21-Jul-88 22:54:34
Rememory                    2588 ----rwed 21-Jul-88 23:29:25
Rememory                    5812 ----rwed 21-Jul-88 22:54:34
l                            Dir ----rwed 17-Nov-88 23:47:40
libs                         Dir ----rwed 17-Nov-88 23:55:16
devs                         Dir ----rwed 17-Nov-88 23:53:21
t                            Dir ----rwed 07-Nov-88 10:02:13
c                            Dir ----rwed 18-Nov-88 00:11:53
FileReader.info             1894 ----rwed 22-Jul-88 01:28:22
PD.pic                      7616 ----rwed 07-Nov-88 08:49:40
s                            Dir ----rwed 07-Nov-88 10:02:14
Laser Chess                13537 ----rwed 14-Apr-87 16:39:58
VirusKillers                 Dir ----rwed 30-Mar-89 13:08:29
Climber5                    3628 ----rwed 21-Jul-88 23:29:18
Jump Ball.info              3590 ----rwed 22-Jul-88 00:39:48
Biker Dave                  6382 ----rwed 21-Jul-88 22:44:53
V.Killers.info               894 ----rwed 07-Nov-88 09:20:42
54 files - 7 directories - 820 blocks used
 
Directory "df0:l" is empty
 
Directory "df0:libs"
mathtrans.library           4280 ----rw-d 17-Nov-88 23:54:47
icon.library                5896 ----rw-d 17-Nov-88 23:54:53
translator.library         10592 ----rw-d 17-Nov-88 23:54:59
info.library               16372 ----rw-d 17-Nov-88 23:55:05
mathieeedoubbas.library     4728 ----rw-d 17-Nov-88 23:55:10
version.library              404 ----rw-d 17-Nov-88 23:55:12
diskfont.library            4900 ----rw-d 17-Nov-88 23:55:15
mathieeedoubtrans.library   15620 ----rw-d 17-Nov-88 23:55:21
8 files - 134 blocks used
 
Directory "df0:devs"
serial.device               5380 ----rw-d 17-Nov-88 23:52:02
narrator.device            23280 ----rw-d 17-Nov-88 23:52:41
keymaps                      Dir ----rwed 17-Nov-88 23:52:07
parallel.device             1812 ----rw-d 17-Nov-88 23:52:12
MountList                   2991 ----rw-d 17-Nov-88 23:52:16
clipboard.device            6672 ----rw-d 17-Nov-88 23:52:21
printer.device             27044 ----rw-d 17-Nov-88 23:52:32
printers                     Dir ----rwed 17-Nov-88 23:54:24
clipboards                   Dir ----rwed 17-Nov-88 23:53:16
ramdrive.device             2128 ----rw-d 17-Nov-88 23:53:20
system-configuration         232 ----rw-d 17-Nov-88 23:53:22
8 files - 3 directories - 154 blocks used
 
Directory "df0:devs/keymaps"
usa0                         992 ----rw-d 17-Nov-88 23:52:06
usa1                        1328 ----rw-d 17-Nov-88 23:52:09
2 files - 7 blocks used
 
Directory "df0:devs/printers"
CBM_MPS1000                 5932 ----rw-d 17-Nov-88 23:52:54
generic                     1096 ----rw-d 17-Nov-88 23:52:55
Xerox_4020                  6524 ----rw-d 17-Nov-88 23:53:00
HP_PaintJet                 6960 ----rw-d 17-Nov-88 23:53:05
HP_LaserJet                 5624 ----rw-d 17-Nov-88 23:53:09
EpsonX[CBM_MPS-1250]        6824 ----rw-d 17-Nov-88 23:53:14
6 files - 73 blocks used
 
Directory "df0:devs/clipboards" is empty
 
Directory "df0:t"
ed-backup                    260 ----rwed 18-Nov-88 00:10:40
1 file - 2 blocks used
 
Directory "df0:c"
loadwb                      2644 ----rwed 17-Nov-88 23:50:15
endcli                       692 --p-rwed 17-Nov-88 23:50:24
AddBuffers                   876 --p-rwed 18-Nov-88 00:11:19
Binddrivers                 2920 ----rwed 18-Nov-88 00:11:50
SetClock                    4556 ----rwed 18-Nov-88 00:11:27
Echo                         564 --p-rwed 18-Nov-88 00:11:54
6 files - 33 blocks used
 
Directory "df0:s"
startup-sequence             281 ----rwed 07-Nov-88 10:02:16
1 file - 2 blocks used
 
Directory "df0:VirusKillers"
How-to-use-Viruscheck.doc    2771 ----rwed 08-Mar-91 10:39:41
.info                         74 ----rwed 30-Mar-89 13:08:29
How-to-use-Viruscheck.doc.info    1080 ----rwed 08-Mar-91 10:39:46
Most                       16948 ----rwed 08-Mar-91 10:39:51
Virus_Checker              15396 ----rwed 08-Mar-91 10:39:58
Virus_Checker.doc          24194 ----rwed 08-Mar-91 10:40:06
Virus_Checker.doc.info      1080 ----rwed 08-Mar-91 10:40:09
Virus_Checker.info         15327 ----rwed 08-Mar-91 10:40:15
8 files - 164 blocks used
 
TOTAL: 94 files - 10 directories - 1389 blocks used

Compared with the disk's contents as revealed by mapping the blocks, six instances of the file entry 'Rememory' are supernumary, and the file entries 'Word War.info', 'Disk.info', 'Jump Ball', 'Climber 5', 'troybw', 'Most'. 'Canfield' and 'WordWar' are missing.

The validation error message is caused by an overwritten file header (resulting in one of the orphan files found on the disk). The bitmap pointer and flag in the root block are zeroed out, so the boot block is being used as an (invalid) bitmap. I'm assuming that the disk cannot be validated because the OS is preventing the boot block from being overwritten - thus the disk image is unmodified when it is ejected.

The only problem with this analysis is that it doesn't explain the missing 8 valid files. The standard OFS 1.3 boot block is mostly zeroed out, which would indicate that most disk blocks are in use - and certainly Blocks 386 and up.

Tomorrow, I will modify the root sector to point to each of the four existing bitmaps in turn to try to gauge which, if any, is the current one and also which of the orphan files are relevant. If it's necessary to construct a new bitmap, I will place it in an unused block to avoid destroying any data.

In the meantime, if anyone can help by suggesting what any of the orphan files might be from their size, that would be appreciated. I may eventually upload the files as an attachment to see if anyone can recognize them from the code.

prowler · 11 January 2012, 23:57

Quote:

Originally Posted by prowler

The validation error message is caused by an overwritten file header (resulting in one of the orphan files found on the disk). The bitmap pointer and flag in the root block are zeroed out, so the boot block is being used as an (invalid) bitmap. I'm assuming that the disk cannot be validated because the OS is preventing the boot block from being overwritten - thus the disk image is unmodified when it is ejected.

The only problem with this analysis is that it doesn't explain the missing 8 valid files. The standard OFS 1.3 boot block is mostly zeroed out, which would indicate that most disk blocks are in use - and certainly Blocks 386 and up.

This evening, in an effort to get those missing files to show up, I modified the bitmap pointer in the root block to point to the second boot block, which is full of zeroes, thus indicating all disk blocks are in use.

WinUAE again mounted the image as an AmigaDOS disk, but there was no detectable change in the disk's behaviour from previously. Evidently there is something going on here that I don't yet understand.

I will get this disk fixed. It's now time to read the Amiga Disk File FAQs, study the entries in the directory blocks and then create a new VALID bitmap, though I would still like to try the existing bitmaps first.

Just before I switched off the emulation, I tried to undelete the missing files from the CLI, but in each case all I got was the error message "File not found...".

Still, this is a lot more interesting than mapping the disk blocks.

prowler · 12 January 2012, 23:27

Now, at last, after studying the entries in the directory blocks, I'm beginning to understand what's going on here.

I can't see anything amiss in the subdirectory blocks, but there are only 44 hash table entries in the Root Block; 6 of these point to directories, and 7 point to missing (orphan) file headers. And yet, there are 56 valid root directory file headers on the disk and the 's' directory entry is missing, which means that at least 25 files and the 's' directory have been deleted from the root of the disk.

To undelete a file, the full path and filename must be known and the file header block and all its data blocks must be intact and marked as unused in the bitmap. Clearly, the 8 missing files were prevented yesterday from being undeleted for want of a valid bitmap.

The bitmap evidently holds the key to fixing this disk, and I'll get started on that tomorrow.

prowler · 15 January 2012, 00:32

Earlier today, I constructed a bitmap marking as unused all those directory and file blocks without directory entries, but it didn't make sense to me that all that lot should have been deleted, so I decided to have a closer look at what the directory entries mean...

Well, sure enough, directory blocks, including the Root, contain a list of block numbers in which the subdirectory and file headers can be found. However, there is room for only 72 entries in each directory block. For this reason, each entry is assigned a "hash value" of 0-71 which defines which files or subdirectories will be assigned to it.

The hash value of a file or directory is computed from its name and length, so these must be known in order to determine the appropriate hash table entry. Clearly, many names can have the same hash value. For this reason, every header block has a "next hash-chain" entry. Header blocks with the same hash value are thus chained together. The last directory or file header block in the chain contains the entry 0.

There are 23 visible next hash-chain entries on this disk, which explains most of the missing hash table entries. The remainder are caused by broken hash-chains resulting from overwritten directory and file header blocks.

This is a much more realistic explanation of why so much information is hidden when the disk is mounted in Workbench. However, it now means that the original names of all missing, damaged or orphan files and directories must be known, headers constructed to re-establish the hash-chains and data block checksum errors fixed before introducing a valid bitmap and recovery of the data can begin.

I'm still convinced that this disk can be fixed. The task of identifying what has been lost will be helped firstly by information I have already found beyond the EOF in last data blocks on the disk and secondly by the fact that all program data can be recreated from information in Compute!'s First and Second Books of Amiga, PDF copies of which are available online.

prowler · 15 January 2012, 21:48

For the first time since I introduced standard OFS 1.3 Boot Blocks into the Compute Games disk image to get it to mount in WinUAE as an AmigaDOS disk, I have actually fixed something!

The AC Basic Compiler v1.2 disk's AmigaBASIC is an exact replacement for 'amigabasic' on the Compute Games disk, which has its first three data blocks overwritten.

Earlier today, I pasted the first three 488-byte blocks of that program into Disk Blocks 1034, 1036 and 1037 of the Compute Games disk image, recontructed the headers and recalculated the checksums to fix that file. I thought I might as well start with the largest single file on the disk.

This is the first of many fixes which will be required before it is safe to reintroduce a bitmap into the image. As it stands - with no bitmap defined - the disk behaves as if all the blocks are marked as used, but no attempt is made to validate the disk, which allows tinkering without fear of the consequences.

@Ze: If you're interested, I could attach WIP disk images to my posts as I make progress.

Ze Emulatron · 16 January 2012, 01:40

A WIP disk image is not necessary for me, I can wait until it has finished, I had been trying to find the games since 2005 when I got into Amiga Emulation with DOS Fellow and MacUAE 0.8.6 so waiting a little longer can't hurt. From all the images I uploaded I had got 8 games working.

If only more people had bought the disks from Computes First Book of Amiga and Compute's Second Book of Amiga it might have been easier to recover the ADF.

Uploaded with ImageShack.us

prowler · 16 January 2012, 22:18

Quote:

Originally Posted by Ze Emulatron

A WIP disk image is not necessary for me, I can wait until it has finished, I had been trying to find the games since 2005 when I got into Amiga Emulation with DOS Fellow and MacUAE 0.8.6 so waiting a little longer can't hurt. From all the images I uploaded I had got 8 games working.

Fair enough. WIP disk images wouldn't be much use to anyone else but me, TBH.

Quote:

Originally Posted by Ze Emulatron

If only more people had bought the disks from Computes First Book of Amiga and Compute's Second Book of Amiga it might have been easier to recover the ADF.

Well, that would have certainly made it easier. On the other hand, I haven't seen many disks as badly damaged as this one, and that makes it all the more interesting from my point of view.

Earlier this evening, I found a matching file for the damaged 'narrator.device' file on a Workbench 1.3 disk and I have prepared the ten overwritten disk blocks with reconstructed headers to receive the replacement data.

prowler · 17 January 2012, 22:54

The 'devs/narrator.device' file is now fixed!

Turning to the next broken file: earlier this evening, I filled data blocks 25-56 of the 'devs/printer.device' file (Disk Blocks 33-43, 22-32 and 11-20) with zeroes, fixed the headers, recalculated the checksums and wrote back to the disk.

Copied out the 'devs/printer.device' file to the Windows hard drive and compared it to the 'devs/printer.device' file copied out from a Workbench 1.3 disk.

I had noticed that the file sizes are similar (27044 bytes and 26964 bytes, respectively), and even more similar ($69A4 and $6954) in hex notation. Furthermore, the last data block is overwritten, so there is no confirmation of the filesize in the header block. However, the two files are indeed different: the Workbench 1.3 file is printer.device 35.563 (29 Aug 1988), whereas that on the Compute Games disk is 35.548 (21 Apr 1988).

Nevertheless, the overwritten data blocks have been prepared for the replacement data when I find a matching file...

Edit: Found it on X-copy v2.0 © 1989 Cachet disk!

That file will be fixed tomorrow!

prowler · 19 January 2012, 00:07

The 'devs/printer.device' file is now fixed!

Next will be the broken Virus_Checker file if I can find the right one.

I just want to get these miscellaneous files fixed first, because they were responsible for a lot of bad blocks.

prowler · 21 January 2012, 01:50

Quote:

Originally Posted by prowler

Next will be the broken Virus_Checker file if I can find the right one.

This is Virus Checker Version 5.10 by John Veldthuis, dated 08-Mar-91. The licence was changed from PD to Freely Redistributable with effect from Version 5.04, and yet I have been unable to find anything earlier than Version 5.26.

I have filled the seven data blocks 4-10 - Disk Blocks 1445-1451 ($5A5-$5AB) - of the 'VirusKillers/Virus_Checker' file with zeroes, fixed the headers, recalculated the checksums and written back to the disk. This fixes the filesystem errors caused by the overwritten data blocks, but the affected 3146 bytes of the file will have to remain zeroed out for the time being.

If anyone has an archive copy of Virus_Checker V5.10 by John Veldthuis, could they upload it to the Zone for me, please?

I think that the 'PD.pic' file in the root directory will have to share the same fate for the time being. as I have no idea where it originates. That way I can at least get down to the business of fixing the Games files and directories.

prowler · 21 January 2012, 21:19

Well, now I do have knowledge of where the 'PD.pic' file originates.

I filled the four data blocks 13-16 - Disk Blocks 1441-1444 ($5A1-$5A4) - of the 'PD.pic' file with zeroes, fixed the headers, recalculated the checksums and wrote back to the disk.

Copied out the 'PD.pic' file to the Windows hard drive. Paint Shop Pro 6 reports that it's not a valid PICTOR/PC PAINT PIC file. It's actually a 320x256 16-colour 72PPI interlaced bitmap and, after renaming it to 'PD.iff', it turns out to be a PD disks order form from PublicWare, P.O.Box 35-622, Browns Bay, Auckland.

@Ze: Do you have an uncorrupted copy of this file on any of your other disks you can upload for me, please?

Ze Emulatron · 22 January 2012, 05:19

Quote:

Originally Posted by prowler

@Ze: Do you have an uncorrupted copy of this file on any of your other disks you can upload for me, please?

I'll have a look but I think I chucked away the other copies of the disk because they didn't work.

prowler · 23 January 2012, 00:54

Quote:

Originally Posted by Ze Emulatron

I'll have a look but I think I chucked away the other copies of the disk because they didn't work.

That's a shame. I can't recover what's been overwritten. Several copies of this disk from back in the day may have solved that problem.

I have found the Virus Checker V5.06 executable only on a November 1990 Demo disk.

I'm not familiar with how the Virus Checker was distributed back then, but both 'How-to-use-Viruscheck.doc' and 'How-to-use-Viruscheck.doc.info' in the 'VirusKillers' directory on the Compute Games disk are at version 5.06, while the rest are at version 5.10. Version 5.10 may therefore have been distributed as an update.

Ze Emulatron · 23 January 2012, 02:51

Quote:

Originally Posted by Ze Emulatron

Quote:

Originally Posted by prowler

@Ze: Do you have an uncorrupted copy of this file on any of your other disks you can upload for me, please?

I'll have a look but I think I chucked away the other copies of the disk because they didn't work.

I couldn't find the copies of the disk I used to have, but I believe that an uncorrupted copy of the file is on Compute Games DiskDoctored.adf, maybe Diskdoctor can be helpful on occasion.

I opened PD.pic from Compute Games DiskDoctored.adf with SView5 for windows and this is what it showed.

Uploaded with ImageShack.us

Zoned a zipped PD.Pic file from Compute Games DiskDoctored.adf, hopefully Windows didn't alter the file.

prowler · 23 January 2012, 21:55

Quote:

Originally Posted by Ze Emulatron

I couldn't find the copies of the disk I used to have, but I believe that an uncorrupted copy of the file is on Compute Games DiskDoctored.adf, maybe Diskdoctor can be helpful on occasion.

Wow! I'm impressed! It hadn't occurred to me to look for it on any of your DiskDoctored or DiskSalved disk images!

DiskDoctor has just gone up a good deal in my estimation.

I just don't know from where in the disk image I'm working on it pulled the rest of that file from!

It's got to be in there somewhere, and if I can find out how that was done I will have learned something well worth knowing.

Quote:

Originally Posted by Ze Emulatron

I opened PD.pic from Compute Games DiskDoctored.adf with SView5 for windows and this is what it showed.

Magic!

Quote:

Originally Posted by Ze Emulatron

Zoned a zipped PD.Pic file from Compute Games DiskDoctored.adf, hopefully Windows didn't alter the file.

No, it's a perfect copy!

Thankyou very much, mate!

It occured to me that the hash values of files and directories still to be assigned to the Root directory hash table and/or hash-chains can be discovered by creating files or directories with the same name on an empty disk image and noting where they fall, and that's what I have been doing earlier this evening. It will also help me identify the orphan files.

prowler · 25 January 2012, 00:33

Hi Ze,

I have some good news and some bad news, but we should be able to find a solution for the latter.

It may not be DiskDoctor after all which was responsible for recovering the 'PD.pic' file from the Compute Games disk.

Please make sure you read the following carefully to grasp the implications:

Earlier this evening, I repaired both the 'VirusKillers/Virus_Checker' and 'PD.pic' files! on my WIP disk image by importing Disk Blocks 1441-1451 (Track 65, Head 1) from the DiskDoctored disk image.

These 11 disk blocks are each overwritten with a copy of Disk Block 1440 (Track 65, Head 0, Sector 10) in the Nibble-copied disk image you uploaded for me, but they are all faithfully preserved in the DiskDoctored disk image you had uploaded earlier!

Further, I have discovered that Disk Blocks 253-263 (Track 11, Head 1), which are each overwritten with a copy of Disk Block 252 (Track 11, Head 0, Sector 10) on the Nibble-copied disk image and Disk Blocks 1034-1044 (Track 47, Head 0) which are each overwritten with a copy of Disk Block 1033 (Track 46, Head 1, Sector 10) on the Nibble-copied disk image are all present and correct on the DiskDoctored disk image as well!

From this I concluded that, for some reason, the Nibble-copied disk you had made earlier and then DiskDoctored must have been more complete than the one you made for me later.

But, since then I have discovered that the DiskDoctored disk image has Disk Blocks 341-351 (Track 15, Head 1) each overwritten with a copy of Disk Block 340 (Track 15, Head 0, Sector 10), Disk Blocks 1705-1715 (Track 77, Head 1) each overwritten with a copy of Disk Block 1704 (Track 77, Head 0, Sector 10) and Disk Blocks 1738-1748 (Track 79, Head 0) each overwritten with a copy of Disk Block 1737 (Track 78, Head 1, Sector 10), whereas all those disk blocks are faithfully preserved in the Nibble-copied disk you uploaded for me.

Thus, either both nibble-copied disks you made, or the images you made of them, appear to have errors of this type, but at different places.

Unfortunately, there are more of these errors which occur at the same places in both images affecting Disk Blocks 968-978 (Track 44, Head 0) and 1078-1088 (Track 49, Head 0).

I have no idea what might have caused these errors except that this random behaviour is vaguely virus-like.

Whatever the cause, it might be possible to get good captures of Track 44, Head 0 and Track 49, Head 0, which are still missing, by repeating the Nibble-copy process.

Tomorrow, I will import Disk Blocks 253-263 and 1034-1044 from the DiskDoctored disk image into my WIP image. This should bring about a good few fixes which I'll post the details of then.

(Actually, I have already repaired Disk Blocks 1034, 1036 and 1037 in my WIP image by importing AmigaBASIC data from the AC-Basic Compiler v1.2 disk.)

Ze Emulatron · 25 January 2012, 01:02

Quote:

Originally Posted by prowler

Thus, either both nibble-copied disks you made, or the images you made of them, appear to have errors of this type, but at different places.

It could have been I nibble copied them on to different brands of new DSHD disks as I don't have any DSDD disks left, I might have also made the copies from DF0: to DF1: in Xcopy one time and from DF1: to DF0: the other time.

It could also be Transdisk when transfering the disks across serial cable and its error tolerance.

I also found another corrupted disk that used to be called Workbench Fonts. I used Disk Salv 2 on the adf I created and it has the drawers Arcade, Strategy and Card Games and some of the games from the Compute Games disk , but it isn't a complete copy, it looks like someone has just deleted all the files they could see from the Workbench Fonts disk copied the drawers and files they could fit and that worked from the Compute Games disk.

I'll make some more copies of the original in my amiga

prowler · 25 January 2012, 01:09

Quote:

Originally Posted by Ze Emulatron

I also found another corrupted disk that used to be called Workbench Fonts. I used Disk Salv 2 on the adf I created and it has the drawers Arcade, Strategy and Card Games and some of the games from the Compute Games disk , but it isn't a complete copy, it looks like someone has just deleted all the files they could see from the Workbench Fonts disk copied the drawers and files they could fit and that worked from the Compute Games disk.

Hey, that might help. Do you think you could upload an image of that one for me, please?

Quote:

Originally Posted by Ze Emulatron

I'll make some more copies of the original in my amiga

Thanks, mate! I'm a a bit more confident of success with this disk following today's breakthrough.

15 January 2012, 00:32	#46
prowler Global Moderator Join Date: Aug 2008 Location: Sidcup, England Posts: 10,300	Earlier today, I constructed a bitmap marking as unused all those directory and file blocks without directory entries, but it didn't make sense to me that all that lot should have been deleted, so I decided to have a closer look at what the directory entries mean... Well, sure enough, directory blocks, including the Root, contain a list of block numbers in which the subdirectory and file headers can be found. However, there is room for only 72 entries in each directory block. For this reason, each entry is assigned a "hash value" of 0-71 which defines which files or subdirectories will be assigned to it. The hash value of a file or directory is computed from its name and length, so these must be known in order to determine the appropriate hash table entry. Clearly, many names can have the same hash value. For this reason, every header block has a "next hash-chain" entry. Header blocks with the same hash value are thus chained together. The last directory or file header block in the chain contains the entry 0. There are 23 visible next hash-chain entries on this disk, which explains most of the missing hash table entries. The remainder are caused by broken hash-chains resulting from overwritten directory and file header blocks. This is a much more realistic explanation of why so much information is hidden when the disk is mounted in Workbench. However, it now means that the original names of all missing, damaged or orphan files and directories must be known, headers constructed to re-establish the hash-chains and data block checksum errors fixed before introducing a valid bitmap and recovery of the data can begin. I'm still convinced that this disk can be fixed. The task of identifying what has been lost will be helped firstly by information I have already found beyond the EOF in last data blocks on the disk and secondly by the fact that all program data can be recreated from information in Compute!'s First and Second Books of Amiga, PDF copies of which are available online. Last edited by prowler; 15 January 2012 at 21:49. Reason: Missed one visible next hash-chain entry :O

15 January 2012, 21:48	#47
prowler Global Moderator Join Date: Aug 2008 Location: Sidcup, England Posts: 10,300	For the first time since I introduced standard OFS 1.3 Boot Blocks into the Compute Games disk image to get it to mount in WinUAE as an AmigaDOS disk, I have actually fixed something! The AC Basic Compiler v1.2 disk's AmigaBASIC is an exact replacement for 'amigabasic' on the Compute Games disk, which has its first three data blocks overwritten. Earlier today, I pasted the first three 488-byte blocks of that program into Disk Blocks 1034, 1036 and 1037 of the Compute Games disk image, recontructed the headers and recalculated the checksums to fix that file. I thought I might as well start with the largest single file on the disk. This is the first of many fixes which will be required before it is safe to reintroduce a bitmap into the image. As it stands - with no bitmap defined - the disk behaves as if all the blocks are marked as used, but no attempt is made to validate the disk, which allows tinkering without fear of the consequences. @Ze: If you're interested, I could attach WIP disk images to my posts as I make progress. Last edited by prowler; 16 January 2012 at 22:10.

17 January 2012, 22:54	#50
prowler Global Moderator Join Date: Aug 2008 Location: Sidcup, England Posts: 10,300	The 'devs/narrator.device' file is now fixed! Turning to the next broken file: earlier this evening, I filled data blocks 25-56 of the 'devs/printer.device' file (Disk Blocks 33-43, 22-32 and 11-20) with zeroes, fixed the headers, recalculated the checksums and wrote back to the disk. Copied out the 'devs/printer.device' file to the Windows hard drive and compared it to the 'devs/printer.device' file copied out from a Workbench 1.3 disk. I had noticed that the file sizes are similar (27044 bytes and 26964 bytes, respectively), and even more similar ($69A4 and $6954) in hex notation. Furthermore, the last data block is overwritten, so there is no confirmation of the filesize in the header block. However, the two files are indeed different: the Workbench 1.3 file is printer.device 35.563 (29 Aug 1988), whereas that on the Compute Games disk is 35.548 (21 Apr 1988). Nevertheless, the overwritten data blocks have been prepared for the replacement data when I find a matching file... Edit: Found it on X-copy v2.0 © 1989 Cachet disk! That file will be fixed tomorrow! Last edited by prowler; 18 January 2012 at 01:05. Reason: Found it!

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08 January 2012, 03:56	#41
Ze Emulatron Registered User Join Date: Nov 2010 Location: Invercargill, New Zealand Posts: 176	Thanks for all the effort you have put in, I have been watching the thread but just haven't had anything to add.

12 January 2012, 23:27	#45
prowler Global Moderator Join Date: Aug 2008 Location: Sidcup, England Posts: 10,300	Now, at last, after studying the entries in the directory blocks, I'm beginning to understand what's going on here. I can't see anything amiss in the subdirectory blocks, but there are only 44 hash table entries in the Root Block; 6 of these point to directories, and 7 point to missing (orphan) file headers. And yet, there are 56 valid root directory file headers on the disk and the 's' directory entry is missing, which means that at least 25 files and the 's' directory have been deleted from the root of the disk. To undelete a file, the full path and filename must be known and the file header block and all its data blocks must be intact and marked as unused in the bitmap. Clearly, the 8 missing files were prevented yesterday from being undeleted for want of a valid bitmap. The bitmap evidently holds the key to fixing this disk, and I'll get started on that tomorrow.

16 January 2012, 01:40	#48
Ze Emulatron Registered User Join Date: Nov 2010 Location: Invercargill, New Zealand Posts: 176	A WIP disk image is not necessary for me, I can wait until it has finished, I had been trying to find the games since 2005 when I got into Amiga Emulation with DOS Fellow and MacUAE 0.8.6 so waiting a little longer can't hurt. From all the images I uploaded I had got 8 games working. If only more people had bought the disks from Computes First Book of Amiga and Compute's Second Book of Amiga it might have been easier to recover the ADF. Uploaded with ImageShack.us

19 January 2012, 00:07	#51
prowler Global Moderator Join Date: Aug 2008 Location: Sidcup, England Posts: 10,300	The 'devs/printer.device' file is now fixed! Next will be the broken Virus_Checker file if I can find the right one. I just want to get these miscellaneous files fixed first, because they were responsible for a lot of bad blocks.

25 January 2012, 00:33	#58
prowler Global Moderator Join Date: Aug 2008 Location: Sidcup, England Posts: 10,300	Hi Ze, I have some good news and some bad news, but we should be able to find a solution for the latter. It may not be DiskDoctor after all which was responsible for recovering the 'PD.pic' file from the Compute Games disk. Please make sure you read the following carefully to grasp the implications: Earlier this evening, I repaired both the 'VirusKillers/Virus_Checker' and 'PD.pic' files! on my WIP disk image by importing Disk Blocks 1441-1451 (Track 65, Head 1) from the DiskDoctored disk image. These 11 disk blocks are each overwritten with a copy of Disk Block 1440 (Track 65, Head 0, Sector 10) in the Nibble-copied disk image you uploaded for me, but they are all faithfully preserved in the DiskDoctored disk image you had uploaded earlier! Further, I have discovered that Disk Blocks 253-263 (Track 11, Head 1), which are each overwritten with a copy of Disk Block 252 (Track 11, Head 0, Sector 10) on the Nibble-copied disk image and Disk Blocks 1034-1044 (Track 47, Head 0) which are each overwritten with a copy of Disk Block 1033 (Track 46, Head 1, Sector 10) on the Nibble-copied disk image are all present and correct on the DiskDoctored disk image as well! From this I concluded that, for some reason, the Nibble-copied disk you had made earlier and then DiskDoctored must have been more complete than the one you made for me later. But, since then I have discovered that the DiskDoctored disk image has Disk Blocks 341-351 (Track 15, Head 1) each overwritten with a copy of Disk Block 340 (Track 15, Head 0, Sector 10), Disk Blocks 1705-1715 (Track 77, Head 1) each overwritten with a copy of Disk Block 1704 (Track 77, Head 0, Sector 10) and Disk Blocks 1738-1748 (Track 79, Head 0) each overwritten with a copy of Disk Block 1737 (Track 78, Head 1, Sector 10), whereas all those disk blocks are faithfully preserved in the Nibble-copied disk you uploaded for me. Thus, either both nibble-copied disks you made, or the images you made of them, appear to have errors of this type, but at different places. Unfortunately, there are more of these errors which occur at the same places in both images affecting Disk Blocks 968-978 (Track 44, Head 0) and 1078-1088 (Track 49, Head 0). I have no idea what might have caused these errors except that this random behaviour is vaguely virus-like. Whatever the cause, it might be possible to get good captures of Track 44, Head 0 and Track 49, Head 0, which are still missing, by repeating the Nibble-copy process. Tomorrow, I will import Disk Blocks 253-263 and 1034-1044 from the DiskDoctored disk image into my WIP image. This should bring about a good few fixes which I'll post the details of then. (Actually, I have already repaired Disk Blocks 1034, 1036 and 1037 in my WIP image by importing AmigaBASIC data from the AC-Basic Compiler v1.2 disk.)

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