Amiga questions you've always been too embarrassed to ask

[malko]

Originally Posted by StingRay

ADF is just a plain 1:1 image of an Amiga disk. It could be created back in the day already as long as you were able to read the disk into memory and save it to a file. Back then it wasn't called ADF of course but the "format" as such always existed. I for one for example often used ASM-One to read a disk completely into memory and save it. And I did that as early as 1991.

So more a "wording" question. OK I stick to it .

Originally Posted by StingRay

Besides, DMS has quite a few bugs so you can easily end up with archives containing wrong/broken data!

Do I read you correctly ? I know that some compressed copy of DMS had issues (this is the reason I used it without compression), but do you mean that these DMS bugs were also affecting uncompressed 1:1 DMS copy ?
(not that I use DMS as today, just curious ).

[StingRay]

Originally Posted by malko

So more a "wording" question. OK I stick to it .

It's not just about the wording. I was trying to point out that ADF didn't "reinvent the wheel" as you claimed. The "format" always existed on Amiga. Contrary to DMS.

Do I read you correctly ? I know that some compressed copy of DMS had issues (this is the reason I used it without compression), but do you mean that these DMS bugs were also affecting uncompressed 1:1 DMS copy ?
(not that I use DMS as today, just curious ).

The bugs are in the DMS code and have nothing to do with the DMS binary being crunched or not.

[drHirudo]

There is also the .adz format, which is better than DMS and more portable.

From Wikipedia on Amiga Disk File

An ADZ file is an ADF file that has been compressed with gzip. The typical file extension is ".adz", derived from ".adf.gz".

I remember being able to directly create adz files with TransADF

Edit: More info:

DMS
ADF files were sometimes compressed using the Disk Masher System, resulting in .dms files.

The Disk Masher System (.dms) is an often used method on the Amiga, to create a compressed image of a disk (usually floppy). The disk is read block-by-block, and thus its data structure is maintained. DMS won approval particularly in the demo scene and the Warez scene, since with this tool, disk images could generally be transferred easily with telecommunication modems to mailbox networks like FidoNet for efficient distribution.[1]

The DiskMasher format is copyright-protected and has problems storing particular bit sequences due to bugs in the compression algorithm, but was widely used in the pirate and demo scenes. To avoid these issues, a number of other disk compressors were developed that used alternative disk reading and compression methods, for instance, xDM[2] or XAD (software).

[Amiga1992]

.ADZ is silly.

[malko]

Hummm... I am becoming confuse with all the answers received. To resume what I understood (Did I understand correctly ?) :

A- DMS <> ADF
a- in the way they read data from the disk (block-by-block VS track-by-track)
b- in the way they store data in the generated file

c- DMS == compacted 1:1 copy by default (plain 1:1 copy possible with cmd line options)
d- DMS bugs in code -> usually secure BUT in some special cases results in wrong/broken data
e- DMS is copyright-protected
i- <see link below>

f- ADF == plain 1:1 copy by default
g- ADF no bugs in code -> 100% secure
h- ADF is not copyright-protected

B- DMS == ADF as they both
a- handle only standard DOS disks
b- can handle NDOS disks BUT cannot handle any non-standard disk format.

Point h- may be the reason why ADF has been preferred. And it is understandable .

Edit: Was looking for something else and found this interesting thread regarding DMS & ADF .

[Amiga1992]

Originally Posted by malko

B- DMS == ADF as they both
a- handle only standard DOS disks
b- cannot handle NDOS disks

Did I understand correctly ?

No. Did you read what I wrote above? DMS can handle NDOS disks just fine. It just cannot handle copy protection, long tracks or other things like that. Same with ADF.

DMS is meant to be a compressed format for distribution, and ADF is meant to be a disk image to be used as is. That's your difference, and that is why emulators use ADF.

[JumpingJackson]

I never owned an Amiga back in the day but I like to play with retro tech. But are games supposed to be, or commonly played with the joystick? Or were gamepads popular too?

[Daedalus]

Unfortunately most games stuck with the standard single-button joystick, despite the Amiga supporting multi-button controllers from day 1. A lot of people did use gamepads, and a number of games were made to take advantage of a second button. The CD32 (the last Amiga model released) uses a multi-button pad as standard, though most games are just ports of the standard Amiga versions so even there they often don't take advantage of having lots of buttons. The CD32 pads can be used on any Amiga, and there are patches available for games that add multi-button functionality. See WHDLoad for more information on that.

[malko]

Originally Posted by StingRay

[...] ADF didn't "reinvent the wheel" as you claimed. [...]

My remark was tinged with irony ( ) . Sorry if it was understood differently.

Originally Posted by Akira

No. Did you read what I wrote above?

Of course I did . I am not the impolite/coarse type to ask a question and not read the answer .

Originally Posted by Akira

DMS can handle NDOS disks just fine. It just cannot handle copy protection, long tracks or other things like that. Same with ADF.

This is also what I "claimed" on my initial question (post #1728) and you confirmed with your post #1737.
After a re-read, I have realised that my answer #1739 to you was not containing the word NDOS contrary to what I thought .

Just I get confused with the various answers received and was not (more) quite sure of anything about it .... So I preferred to summarize, even if it meant writing something wrong.

I have changed point B-b- of my post #1745.

Thank you StingRay, Akira and others

[Gorf]

next question:

why was there never a zorro-board featuring Agnus and Denise (or later Alice and Lisa)?
How hard would it have been to build and support (software) such a card for C=?
Could a modern FPGA-gfx-card like the VA2000 provide such a feature?

[idrougge]

What's the point? Every Zorro-equipped Amiga already has Agnus and Denise.

[Gorf]

Originally Posted by idrougge

What's the point? Every Zorro-equipped Amiga already has Agnus and Denise.

Firstly of course for dual screen usage.

Than we have the nice genlock capability, so you could mix both outputs:
While being in sync such a setup would provide 2*64 -1 colors or 4 play fields.

One could even feed that output to yet an other card....

Imagine that used in an arcade machine - maybe even together with a laserdisc feed and 4 or 6 playfields on top..

you could also shift the colour range of the second chipset a little bit, so it would provide halve-tones between the original output, giving you a palette of 8192 colors

combined with a fickerfixer/amber/mixer you could provide an interleaved mode: highres in 64 colors. (or for AGA 256 with double blitter-speed)

I think that would have been a killer feature in the 80s and also would have been a way to stay competitive in the early 90s...

What would be the technical caveats of such a setup?

[malko]

Link to another EAB thread added in post #1745.

[Jope]

Originally Posted by Gorf

What would be the technical caveats of such a setup?

The problem here is, that Agnus basically is the Amiga. It won't live with another Agnus on the same bus, as it runs the show, taking the bus when it needs to.

You would be looking at something similar to a bridgeboard, but actually containing another Amiga, not a PC, communicating with the host machine via some dual port RAM or some other method.

[Gorf]

Originally Posted by Jope

The problem here is, that Agnus basically is the Amiga. It won't live with another Agnus on the same bus, as it runs the show, taking the bus when it needs to.

Of course it needs to play by the Zorro-Bus rules. It manages its own RAM on the card, similar to how most other gfx-cards work.

some registers would be unused/unavailable but copper and blitter and Denise should be fully working.

Sure you could call it a striped down Amiga, but it would be more things missing than conserve: cpu, cia, Paula, Garry, ports would be gone on such a card.

The registers and the new ChipRAM would be somewhere in zorro2-space and Agnus needs to be able to handle the offset or translate the addresses .... cpu can write to that memory via Zorro-Bus if card is ready. No big difference in function to how it workes with usual ChipRAM

[Jope]

The Agnus probably wouldn't have to care about any offsets in that sense, it can be handled by software before the register write.

I still think the Agnus should be totally isolated in its own microcosm on the zorro board, you're right that the CPU itself is not necessarily needed in this case, I wouldn't necessarily have added that on there either, so maybe the bridgeboard analogy wasn't that good.

But anyway, my reasoning behind the "amiga bridgeboard" idea was, that the Agnus can block anyone from the bus for a long time if you're doing something DMA heavy. This might be easier if there is a separate CPU on the zorro board to handle moving the data from the zorro facing registers into the Agnus itself..

[Gorf]

Originally Posted by Jope

The Agnus probably wouldn't have to care about any offsets in that sense, it can be handled by software before the register write.

I still think the Agnus should be totally isolated in its own microcosm on the zorro board, you're right that the CPU itself is not needed in this case, I wouldn't have added that on there either, so maybe the bridgeboard analogy wasn't that good.

than we were talking about the same thing here. Agnus and Denise get its own RAM on a board, where blitting and so on is done. CPU on the mainboard writes to gfx-ram and registers via Zorro.

Advantage of such a card: it is far more compatible to graphics.library and Intuition - software needs only address-transtation options.

If such a card would have been available even as late as 1991 with poor old ECS, I would have bought one for my A3000 immediately!
To be honest: today I would buy such a card ...

[Gorf]

But anyway, my reasoning behind the "amiga bridgeboard" idea was, that the Agnus can block anyone from the bus for a long time if you're doing something DMA heavy. This might be easier if there is a separate CPU on the zorro board to handle moving the data from the zorro facing registers into the Agnus itself..

I think a second cpu would make things far more complicated and unnecessary expensive. Sure the CPU has to wait on the Zorro-bus until Agnus is ready - but I do not see a big difference to usual ChipRAM behavior here. And there are plenty other Zorro-cards behaving the same way.
Being freed of audio, floppy and so on, the DMA stress-level would be lower on such a card anyways.

[malko]

Originally Posted by Gorf

[...] If such a card would have been available even as late as 1991 with poor old ECS, I would have bought one for my A3000 immediately!
To be honest: today I would buy such a card ...

Not sure as today, but back in 1991, I would have bought one for A2000 for sure !

[DamienD]

...this post is probably better suited in this thread.

Could have just moved but then it would get lost in the pages and not the most recent question:

Originally Posted by Viceroy

Hi

The extended ADF's folder on the FTP.
Could someone explain exactly what these are. I was wondering if these were just the SPS versions of games with protection in, or are they something different?
Cheers