Emulator Floppy Formats

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Pernod
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Emulator Floppy Formats

Postby Pernod » Mon Jun 13, 2016 8:34 pm

There's plenty of info out there on BBC formats, ssd/dsd/adm/adl, etc. but not a great deal on Archimedes formats. I'm adding the common formats to MAME and need definitive ways to identify each format.

A few questions:
- The common format is adf and most images are either 800K or 1600K, are these interleaved like adl?
- Are there any identifying bytes in an adf such as sector counts?
- Some adf files (TOSEC) are not quite 800K, some are under and a couple are 801K. Bad dumps or truncated like ssd?
- Found some arc files, how do these differ from adf?

Any other common formats out there?
- Nigel

BBC Model B, ATPL Sidewise, Acorn Speech, 2xWatford Floppy Drives, AMX Mouse, Viglen case, etc.

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Re: Emulator Floppy Formats

Postby geraldholdsworth » Mon Jun 13, 2016 8:52 pm

I've been trying to write a Windows utility to read new map ADFS files. David Boddie has done some work on this, including writing a Python script for reading them (the link escapes me at this moment in time). This post may also help:
http://compgroups.net/comp.sys.acorn.pr ... ps/1302965
There's also a description of the format at MDFS:
http://mdfs.net/Docs/Comp/Disk/Format/NewMap
as well as the PRMs.
Gerald Holdsworth
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www.reptonresourcepage.co.uk

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Re: Emulator Floppy Formats

Postby SarahWalker » Mon Jun 13, 2016 9:26 pm

Pernod wrote:There's plenty of info out there on BBC formats, ssd/dsd/adm/adl, etc. but not a great deal on Archimedes formats. I'm adding the common formats to MAME and need definitive ways to identify each format.

A few questions:
- The common format is adf and most images are either 800K or 1600K, are these interleaved like adl?

Yes.

- Are there any identifying bytes in an adf such as sector counts?

Nope, raw sector dumps.

- Some adf files (TOSEC) are not quite 800K, some are under and a couple are 801K. Bad dumps or truncated like ssd?

Bad dumps.

- Found some arc files, how do these differ from adf?

These are ArcFS archives, and not disk images.

Any other common formats out there?

APD, which is an MFM bitstream format (have a look in the Arculator source), FDI, and JFD.

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Re: Emulator Floppy Formats

Postby jgharston » Mon Jun 13, 2016 9:29 pm

Pernod wrote:- The common format is adf and most images are either 800K or 1600K, are these interleaved like adl?

No, ADF is a pure dump of the filesystem. The data for sector N is at exactly N*SECTORSIZE bytes into the image. However, that filesystem is written to a physical floppy disk with interleaved sides, logical sectors 0 to T-1 are on track 0 side 0, logical sectors T to 2T-1 are on track 0 side 1, logical sectors 2T to 3T-1 are on track 1 side 0, etc. The image file is purely sector 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,etc.etc.etc. with no skippping back and forth, all the way to the end.

It can be any size, if the image size is shorter than that filesystem's 'number of sectors' in the free space map, the 'nonexistant' sectors past the end of the image file are unused.

Code: Select all

$ bbcbasic
PDP11 BBC BASIC IV Version 0.25
(C) Copyright J.G.Harston 1989,2005-2015
>_

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Re: Emulator Floppy Formats

Postby sirbod » Tue Jun 14, 2016 6:53 am

Mirroring what @SarahWalker has stated:

Pernod wrote:- The common format is adf and most images are either 800K or 1600K, are these interleaved like adl?

Yes, interleaved from a 1772 perspective, as ADFS stores alternative tracks on alternative sides of the disc. From a software perspective it's one continual dump of the data from tracks 0 to 79.
Pernod wrote:- Are there any identifying bytes in an adf such as sector counts?

No, but detecting an ADF is simply a matter of ruling out the other types first and falling back to ADF if all else fails, which is what ADFFS does.
Pernod wrote:- Some adf files (TOSEC) are not quite 800K, some are under and a couple are 801K. Bad dumps or truncated like ssd?

Bad dumps, of which there are a lot :(
They should be either 640K, 800K or 1600K exactly depending on the original floppy format.
Pernod wrote:- Found some arc files, how do these differ from adf?

Archives, ignore them
Pernod wrote:Any other common formats out there?

APD, JFD, FDI and IPF - although in six years I've yet to find examples of either FDI or IPF, so haven't supported them in ADFFS. IPF is an undocumented, proprietary format created by the Software Preservation Society, decoding libraries can be downloaded from their site. Here's the documentation on APD and JFD that I wrote, that's included in ADFFS:
!Structure.txt
(9.12 KiB) Downloaded 41 times

APD, FDI and IPF are all low level formats at 1772 bitstream level. JFD is at the FileCore level after it's been decoded by the 1772 and passed through ADFS, so JFD's that include DiscOp 3 (read track) data can't be emulated outside of ADFFS - there's only a few games that use this, so the majority of JFD's could be supported by an emulator, certainly all the games released to date should work. I believe the next release of Arculator supports JFD.
Last edited by sirbod on Tue Jun 14, 2016 8:07 pm, edited 1 time in total.

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Re: Emulator Floppy Formats

Postby Pernod » Tue Jun 14, 2016 11:26 am

Thanks everyone for the informative replies. I intend to support ADF, JFD, and APD at this time. I have plenty of examples of ADF and JFD, and also managed to find the APD's.
- Nigel

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Re: Emulator Floppy Formats

Postby Pernod » Mon Jan 16, 2017 9:30 pm

Archimedes emulation in MAME has progressed significantly in the past couple of months, and most games are now playable. It currently supports ADF and as of 0.182 will support APD too. Now to see what I can do to support JFD.

My APD testing was a little limited due having only a handful of files to test with. Can anyone point me to a decent collection, PM me if preferable.
- Nigel

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Re: Emulator Floppy Formats

Postby sirbod » Tue Jan 17, 2017 10:57 am

There's some APD's on Qube Server

The format is described in a text file within the !ADFFS folder, from memory it's three track tables of 166 tracks each (single, double and quad density), the tracks being raw FM/MFM.

For JFD's, the format is again described in a text file within the !ADFFS folder. You can obviously grab examples from the project site.

Unlike APD, JFD sits above the 1772 so might require conversion back to FM/MFM and be a PITA to implement, it doesn't contain track or sector headers, just sector meta data. Arculator supports some JDF files, but I've not looked at how it was implemented, might be worth a look at the source for inspiration.

JFD does have one special case that allows for a complete track dump (Slappit), this does include the track and sector header, but none of these are publicly available.

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Re: Emulator Floppy Formats

Postby hubersn » Wed Jan 18, 2017 9:10 pm

Pernod wrote:Archimedes emulation in MAME has progressed significantly in the past couple of months, and most games are now playable.


Any hints on how to get MAME (0.181) actually to work (as an Archimedes - I managed to get it to emulate an Amstrad CPC6128)? I tried and failed. And haven't been able to find any meaningful docs.

"The selected machine is missing one or more required ROM or CHD images. Please select a different machine."

Any help appreciated. I understand it needs a "ROM set". I found some on the internet and I think I put it into the expected place.

hubersn

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Re: Emulator Floppy Formats

Postby hubersn » Wed Jan 18, 2017 10:58 pm

hubersn wrote:
Pernod wrote:Archimedes emulation in MAME has progressed significantly in the past couple of months, and most games are now playable.


Any hints on how to get MAME (0.181) actually to work (as an Archimedes - I managed to get it to emulate an Amstrad CPC6128)? I tried and failed. And haven't been able to find any meaningful docs.

"The selected machine is missing one or more required ROM or CHD images. Please select a different machine."

Any help appreciated. I understand it needs a "ROM set". I found some on the internet and I think I put it into the expected place.

hubersn


A few hours and countless experiments and doc hunting later...

There must be a dir "aa310" in the MAME's ROM directory. To run RISC OS 3.11 put ic24.rom ic25.rom ic26.rom ic27.rom into that directory. Get a good cmos.ram e.g. from Arculator and put it as cmos_riscos3.bin into that directory. Run MAME from the command line as

mame.exe aa310 -bios 311
(or of course mame64.exe)

and ignore all warnings (like e.g. an incorrect CRC and SHA1 of the cmos file - how can something variable have a fixed checksum???) :-)

I found some old MESS docs that helped a bit: http://www.progettoemma.net/mess/system ... chine=a310

Outdated, but helpful in the end. You can let MAME print out the things it expects via the following command:

mame.exe -listxml aa310

Have fun
hubersn

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Re: Emulator Floppy Formats

Postby Pernod » Wed Jan 18, 2017 11:15 pm

hubersn wrote:and ignore all warnings (like e.g. an incorrect CRC and SHA1 of the cmos file - how can something variable have a fixed checksum???) :-)
I found some old MESS docs that helped a bit: http://www.progettoemma.net/mess/system ... chine=a310

Due to recent developments most third party docs will be outdated. The CMOS checksum is for a good default state, any changes to the CMOS will be in your nvram folder. Check your PM!
- Nigel

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Re: Emulator Floppy Formats

Postby hubersn » Fri Jan 20, 2017 4:18 pm

Pernod wrote:
hubersn wrote:and ignore all warnings (like e.g. an incorrect CRC and SHA1 of the cmos file - how can something variable have a fixed checksum???) :-)
I found some old MESS docs that helped a bit: http://www.progettoemma.net/mess/system ... chine=a310

Due to recent developments most third party docs will be outdated.


I would be happy to read the first party docs, but I am still searching for it.

For arcade machines, it might be sufficient to throw some ROMs in a directory, but for real computers, a bit more information would be nice. I could not even find out where to put the floppy images and how to access them!

Pernod wrote:The CMOS checksum is for a good default state, any changes to the CMOS will be in your nvram folder.


If you want a good default state, you could hardcode it. If the user provides his own CMOS settings, use those. And it is not like a bunch of CMOS settings are copyrighted - if it really needs to be a file, why not distribute it with MAME?

Pernod wrote:Check your PM!


Thanks for that. I am a bit confused about the inconsistency of the ROM naming and format (1 file vs. 4 files). And I don't like the idea of downloading copyrighted files from some online source, when there is a legal source available for small money - which unfortunately uses different names and formats.

Don't get me wrong. I like the idea of having another alternative emulator for Acorn machines available. And it looks like MAME does a competent job of emulating the Arc. But in its current state, it is nearly impossible to test it as an average user. Or maybe I am just missing the obvious place where to find the necessary docs.

Have fun
hubersn

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Re: Emulator Floppy Formats

Postby hubersn » Fri Jan 20, 2017 6:08 pm

hubersn wrote:I could not even find out where to put the floppy images and how to access them!


OK, getting more successful by the hour...

Put the disc images somewhere inside the MAME dir (I think "software" is the default place). The keyboard key to invoke the emulator's menu is Scroll Lock. If, like me, you work on a Notebook that does not have that key, you can select a different one - I chose TAB for easy access (and I haven't found the part of the documentation where the possible key names are specified). So now I start MAME via the following command:

mame64.exe aa310 -uimodekey TAB -bios 311

By pressing TAB and selecting "File Manager", you can choose which floppy image to mount.

Phew!

hubersn

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Re: Emulator Floppy Formats

Postby Pernod » Sat Jan 21, 2017 11:02 pm

sirbod wrote:Unlike APD, JFD sits above the 1772 so might require conversion back to FM/MFM and be a PITA to implement, it doesn't contain track or sector headers, just sector meta data. Arculator supports some JDF files, but I've not looked at how it was implemented, might be worth a look at the source for inspiration.

I've now got preliminary JFD support in MAME, would've been sooner if I didn't mix up my assumed gap sizes. Anyone know what the typical ADFS gap sizes are?

Can you suggest a handful of JFD's that use different protections for testing?
- Nigel

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Re: Emulator Floppy Formats

Postby sirbod » Sun Jan 22, 2017 11:59 pm

Pernod wrote:Anyone know what the typical ADFS gap sizes are?

If I didn't document them in the same document as APD/JFD, they're in PRM2 I believe. Grab PRM2.PDF from the FTP site.
Pernod wrote:Can you suggest a handful of JFD's that use different protections for testing?

Off the top of my head:

Zarch - mixed SD/DD sectors and invalid sector ID's
Slappit - does a full track read
Fire & Ice - QD track, reads past track 160 and expects a list of track ID when it does a full track read (if there's no monsters on level 3, the protection check failed)
Wolfenstein - sector in sector
The Last Ninja - unformatted track
Air Supremacy - sector CRC error
HeroQuest - duplicate sectors

There's also mixed sector sizes, but I don't recall which games use it.

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Re: Emulator Floppy Formats

Postby Pernod » Mon Jan 23, 2017 7:36 pm

The PRM2 was exactly what I needed, thanks.

From your list of suggestions the following are working:
The Last Ninja - unformatted track
Air Supremacy - sector CRC error
HeroQuest - duplicate sectors

I have no idea how to represent sector in sector as a bitstream so those will have to wait for now. I should be able to handle the full track read though, is this the DiscOp3? It looks like DiscOp3 is only used a three images, in two of them it's specified in sector 0 header and the other sector 1 header. So is the DiscOp3 data a full track or a single sector, not clear on this.

In the [Track Table] where a blank track is denoted by FFFFFFFF, does this mean unformatted?

To get an idea of what's in a JFD I wrote a python script to scan a folder of JFD and list all non standard sectors in each image. It also writes out all standard 1024 byte sectors to an ADF of same name. Interestingly it didn't find anything unusual in The Last Ninja and produced an 800K ADF that works! There are about 20 JFD that convert to 800K ADF without finding unusual sectors, though haven't tested them all yet.

Regarding Zarch, the PRM2 specifically states 'You may not vary the data rate or encoding method within a single track'. In MAME I can easily create whole tracks with different encoding but not individual sectors, so this will require some additional work. I have an APD of this that works so not high priority, though it looks like there are a few other titles that require this.

So overall a large amount of JFD's are handled, just need to look at DiscOp3 and mixed density tracks, forget sector in sector.

In your !Structure.txt there's a ConvRec section, is this relevant to what I'm doing or just for reference?
- Nigel

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Re: Emulator Floppy Formats

Postby sirbod » Mon Jan 23, 2017 9:51 pm

Pernod wrote:I have no idea how to represent sector in sector as a bitstream

If it's any help it expects track 159 on disc 1 to look like this:

Code: Select all

25 sectors 0 > 9, sizes 3, 1, 1, 1, 2, 3, 1, 2, 1, 2, 3
 sector 2 bad CRC
 sector 5 bad CRC
 sector 8 bad CRC
 sector 9 bad CRC and nested sectors:
  sector 8, size 3
   sector 8, size 2 bad CRC
    sector 8, size 3
     sector 8, size 3
      sector 8, size 3
       sector 8, size 1 bad CRC
        sector 8, size 2 bad CRC
         sector 8, size 3
          sector 8, size 3
           sector 8, size 3
            sector 8, size 3
             sector 8, size 2
              sector 8, size 1
               sector 8, size 1 terminated early

The APD image should be on the server, manually dump the track with DiscOp 3 to see how it's structured. If I remember correctly, you create the sector ID's one after the other without a data block, only the last sector will contain data.
Pernod wrote:I should be able to handle the full track read though, is this the DiscOp3? It looks like DiscOp3 is only used a three images, in two of them it's specified in sector 0 header and the other sector 1 header. So is the DiscOp3 data a full track or a single sector, not clear on this.

Yes, DiscOp 3. You need to check the sector header at the address being requested, if bit 3 of the option bits is set, the sector data is actually a full DiscOp 3 dump, so you'd just return the data from that sector as FM/MFM instead of reconstructing the track.
Pernod wrote:In the [Track Table] where a blank track is denoted by FFFFFFFF, does this mean unformatted?

Correct. FFFFFFFF denotes the end of the track's sector list, so if there's no sectors it's unformatted.
Pernod wrote:To get an idea of what's in a JFD I wrote a python script to scan a folder of JFD and list all non standard sectors in each image. It also writes out all standard 1024 byte sectors to an ADF of same name. Interestingly it didn't find anything unusual in The Last Ninja and produced an 800K ADF that works!

Neat. With The Last Ninja, track 159 is unformatted. The ADF should be slightly short in length for it to work. There's a few games that use this protection method, so can be made to work in ADF form, provided the emulator returns unformatted if the read is outside of the ADF size.
Pernod wrote:There are about 20 JFD that convert to 800K ADF without finding unusual sectors, though haven't tested them all yet.

I'd expect a lot more than that, JFD's only store sectors that are touched so you'd need to pad the ADF with 1024 bytes for any missing sectors.
Pernod wrote:Regarding Zarch, the PRM2 specifically states 'You may not vary the data rate or encoding method within a single track'. In MAME I can easily create whole tracks with different encoding but not individual sectors, so this will require some additional work. I have an APD of this that works so not high priority, though it looks like there are a few other titles that require this.

The PRM is correct in that you can't create mixed encoding on an Arc. This is the R.A. North protection method. Conqueror, Magic Pockets, Sensible Soccer and Zarch use it. There's possibly a few others I've not specifically looked at (Drop Ship possibly, I recall this has a bespoke protection method that may be a variation).

The disc structure for the protection is:

Code: Select all

- Track 80 has mixed density sectors
- Track 80, 4 x DD 512 byte sectors 240, 241, 242, 243
- Track 80, 4 x SD 512 byte sectors 240, 241, 242, 243
- Track 80, SD and DD sector 243 bad CRC
- Track 80, SD and DD sector 241 bad CRC and nested sector:
- Track 80, SD and DD sector 242
- Track 81, unformatted track
- Tracks 82 to 159, 10 x 128 byte SD sectors 240 > 249

Pernod wrote:In your !Structure.txt there's a ConvRec section, is this relevant to what I'm doing or just for reference?

It's reference and describes how ConvRec stores its internal sector capture table from a recording, so it can replay the recording to create a JFD on an Arc. You can ignore it.

The structure for Fire & Ice incidentally is:

Code: Select all

Disc 1 - Track 157, no sectors
       - Track 158, 19 x 256 byte sectors ID order: 2 > 19, 1
       - Track 159, 19 x 256 byte sectors 0 > 18 all bad ID CRC
       - Track 160 extra track
       - Track 161 quad density track

Disc 2 - Track 0, sector 1 bad CRC

DiscOp 3 on disc 1 expects a list sector ID's, not a track dump
Level 3 has no enemies if disc check fails

Sound like you've made some good progress considering JFD's were never meant to work at emulator level.

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Re: Emulator Floppy Formats

Postby Pernod » Wed Jan 25, 2017 9:38 pm

A little progress with DiscOp3, I have Slappit working but the other RTFM titles don't :(
- Nigel

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Re: Emulator Floppy Formats

Postby sirbod » Thu Jan 26, 2017 9:44 am

Pernod wrote:A little progress with DiscOp3, I have Slappit working but the other RTFM titles don't :(

Odd, if its working for Slappit it should work for the others. If it's any help, I've just looked at the recording files to see what protection they're using:

F1049301 Arc/A3000 Christmas Box, The: Brixx! (1990) (RTFM Software)
F1049302 Arc/A3000 Christmas Box, The: PON! in Winterland (1990) (RTFM Software)

Code: Select all

DiscOp 3 @ C6C00 (track 159) disc size &C8000

F1049303 Arc/A3000 Christmas Box, The: Zap the red weirdos from Mars (1990) (RTFM Software)
F1045201 Bouncer (1991) (RTFM Software)
F1011801 Dominate (1991) (RTFM Software)
F1047501 Rekall (1990) (RTFM Software)

Code: Select all

No protection

F1045601 Slappit (1990) (RTFM Software)

Code: Select all

DiscOp 3 @ A0000 (track 128) disc size &C8000

F1059203 Games Minipack Five: PON! (1990) (Cambridge International Software)

Code: Select all

Picks random tracks to read between:
DiscOp 3 @ 64000 (track 80) disc size &C8000
.. and every track up to
DiscOp 3 @ C4400 (track 157) disc size &C8000

Which of these are you having problems with?

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Re: Emulator Floppy Formats

Postby Pernod » Thu Jan 26, 2017 11:13 am

sirbod wrote:F1049301 Arc/A3000 Christmas Box, The: Brixx! (1990) (RTFM Software)
F1049302 Arc/A3000 Christmas Box, The: PON! in Winterland (1990) (RTFM Software)

It's these two, they eventually produce a 'Disk load error' message. Am heading away for a few days so will be next week before I can investigate further.
- Nigel

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Re: Emulator Floppy Formats

Postby sirbod » Sun Jan 29, 2017 4:22 am

On a similar note, there are a couple of games where JFD's may be missing the protection sectors. These talk to the 1772 directly via IOC and so aren't captured in the recording process. You might be able to help me fix these images by letting me know which track/sector/density they're reading. Known games that use this protection method include:

F1064001 BlastOn (unconfirmed)
F1005701 Bubble Fair
F1007501 Chequered Flag (RO2 version)
F1015301 Fine Racer
F1022001 KerBang!

I suspect some of the other original Eterna releases also do this, but I don't have them all to confirm. They're easy to spot as they only contain a !BOOT file on the floppy.

There's also a few games that need very accurate CPU emulation, that to my knowledge do not currently work under any emulator. "Adventures, classic complication [Philosopher's Quest, Countdown to Doom, Return to Doom..., Kingdom of Hamil, Acheton]" for example. I've spent hours analysing this under the ADFFS JIT simply trying to figure out what on earth the protection code is supposed to be doing, it's very hard to follow as it puts the SVC stack within the code and switches CPU modes.

I think I've already mention the two that require accurate VIDC emulation, Greivous Bodily 'ARM and James Pond 2/2+. The former doesn't work correctly under any emulator.

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Re: Emulator Floppy Formats

Postby ThomasHarte » Mon Jan 30, 2017 2:36 pm

sirbod wrote:APD, JFD, FDI and IPF - although in six years I've yet to find examples of either FDI or IPF, so haven't supported them in ADFFS. IPF is an undocumented, proprietary format created by the Software Preservation Society, decoding libraries can be downloaded from their site.

Far too slow to be of any direct relevance, but IPF only was undocumented. The society seems to have a certain attitude towards the outside world that perhaps isn't enviable, but have at least been persuaded that a proprietary format isn't the way to go. So official documentation is here. I've not read it thoroughly, but having a flick through now it looks like they've avoided the FDI pitfall of adding so many special cases that the thing becomes unwieldy.

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Re: Emulator Floppy Formats

Postby danielj » Mon Jan 30, 2017 4:44 pm

I don't think that documentation is official, it's by dcoolzic, but the sps guys did help him with it iirc..

d.

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Re: Emulator Floppy Formats

Postby ThomasHarte » Mon Jan 30, 2017 4:50 pm

danielj wrote:I don't think that documentation is official, it's by dcoolzic, but the sps guys did help him with it iirc..

d.

You're right; I misread the thread that led me to it. So it is documented, but only by a third party as a consequence of the source code being available. Better than binary reverse engineering, not as good as the word of God.


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