04 January 2018, 16:00 | #1 |
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Amiga Floppy Disk layout
Hi !
In france they are a old edition book from Micro Application : LA BIBLE DE L'AMIGA They're exist 2 Tome (Tome1 and so, Tome2 that is a the same version with correction of tome1) in Tome 1 I have this picture : I think there is an error. The first tracks (so 0), start on Side0 (which is upper, which is the FACE1 on the picture) and, on Amigados have 11 sectors/side If we use the sector information, the eleventh (yes because we start from 00->10 = 11 blocs) sector/bloc is the first sector on other side So for me, it's a mistake in this picture... Blocs 11-21 must be on Face2 on this picture and Blocs 00-10 must be on Face1 on this picture. If anybody confirm this ? Last edited by prowler; 05 January 2018 at 00:55. Reason: Embedded the image for clarity. |
04 January 2018, 17:34 | #2 |
Natteravn
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No. Block 0 (the boot block) starts on the lower side of the disk. Block 11 (first sector of track 1) is on the upper side.
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04 January 2018, 17:49 | #3 |
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Are you sure about this ?
Because when we start a doscopy with X-copy, it start first whith 'UPPER SIDE', So x-copy don't start in block 0? Strange isn't ? With MKIII, a RT 0 2 50000 , go in your way, Start reading Lower side and after Upper. Why X-copy start from upper side ? And burstnibler start from lower side... -_-' And, i think they are not really 'standard' name for Head (0, 1 sometimes even 2). Best is to talk about 'upper' and 'lower' Last edited by Giants; 04 January 2018 at 18:01. |
05 January 2018, 00:29 | #4 |
Natteravn
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I'm pretty sure about it, because I wrote a trackloader which sets CIA-B port B bit 2 (DSKSIDE) to select the lower head, whenever I access an even track. And it reads the data I expect it to read.
According to the Hardware Reference Manual DSKSIDE=0 means upper head and DSKSIDE=1 means lower head. |
05 January 2018, 10:13 | #5 |
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#Block 0 (the boot block) starts on the lower side of the disk.
#...DSKSIDE=0 means upper head and DSKSIDE=1 means lower head. So Start begin from DSKSIDE=1 !? |
05 January 2018, 13:02 | #6 |
Natteravn
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05 January 2018, 17:30 | #7 |
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OK, so This =>
Last edited by Giants; 05 January 2018 at 20:42. Reason: Html error |
27 May 2018, 00:29 | #8 |
Defendit numerus
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Warning.
I arrived quite randomly on this page (I was looking for a utility for MFM conversion ..) and I noticed that former picture can be misleading for those that approach the Amiga floppy system. In the Hardware Reference Manual, as already specified by phx, it's clearly indicated that DSKSIDE*=zero implies the upper head. But this, like many other CIA's signals, is negated. So actually to select lower side you need to write 1 to DSKSIDE*. Sectors count up from cylinder 0 side 0 sector 0 (outer disk position, lower side). Alternatively Amiga uses tracks (where track 0 is [cyl.side]0.0, 1 is 0.1, 2 is 1.0, 3 is 1.1, 4 is 2.0 and so on). The correct version: Code:
Blocks 11-21 (track 1) [Upper head] Side 1 | DSKSIDE*=0 -------------------------------- (cylinder 0) Blocks 00-10 (track 0) [Lower head] Side 0 | DSKSIDE*=1 Last edited by ross; 27 May 2018 at 01:01. Reason: improved my beautiful chart :P |
03 August 2018, 13:12 | #9 |
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Exact !
Thks |
05 April 2023, 18:37 | #10 | |
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Quote:
The manual doesn't say if "zero" means "0 volts" or "side 0". The asterix in DSKSIDE* would imply active low, so 0 volts would mean side 1. But, in my copy of the Amiga Hardware Reference Manual, it's called DSKSIDE, not DSKSIDE*. And anyways, I would be very surprised if Commodore did actually really know whether they had stored block 0 on the upper or lower side : ) (unless they had a good reason to care about sides, like needing to load the bootblock from single-sided disks). The only way to be sure would be to remove or disconnect the lower drive head, or somehow block/erase the magnet field on the lower side. And then test which blocks are still accessible. --- In the UNWARP software, the sides are called TOP and BOT, with the bootblock in block 0 being on TOP side (but there's a 50:50 chance that they got that wrong, and TOP is actually bottom). The trackdisk device functions are also confusing, ETD_FORMAT does use Offset=(track*2+side)*1600h. But ETD_RAWWRITE seems to use Offset=(track*2)+(1-side). Either one seems to have "side" inverted in software, and it might be further inverted in hardware. --- Also in the UNWARP software: That program defaults to allow to write to Track FFFFh (Track -1) up to Track 0052h (Track 82). I know that one may access hidden tracks in range 80..82. But Track -1, is that also possible? Can one issue an extra step, after triggering the track 0 sensor, and before hitting a hard boundary? EDIT: Warp is using Track FFFFh as dummy track number in Text chunks (added via +TEXTFILE in warp commandline), I guess it does never use Track FFFFh in actual data track chunks. Last edited by nocash; 06 April 2023 at 22:19. |
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