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STH Elite disc image

Posted: Wed Sep 11, 2019 6:20 pm
by Diminished
During testing on the Disc Toaster I encountered this Elite image from the Stairway archive:

http://www.stairwaytohell.com/bbc/archi ... /Elite.zip

Downloading and extracting it yields an SSD file of 115456 bytes.

The maximum size for a standard-formatted 40 track disc is 256 bytes per sector * 10 sectors per track * 40 tracks, which gives exactly 102400 bytes.

So, what's with this image? I'm guessing it used some non-standard sector format to squeeze the extra data in there -- can anyone confirm?

Re: STH Elite disc image

Posted: Wed Sep 11, 2019 7:13 pm
by billcarr2005
Diminished wrote:
Wed Sep 11, 2019 6:20 pm

The maximum size for a standard-formatted 40 track disc is 256 bytes per sector * 10 sectors per track * 40 tracks, which gives exactly 102400 bytes.

So, what's with this image? I'm guessing it used some non-standard sector format to squeeze the extra data in there -- can anyone confirm?
It's an 80 track disc, with only sectors with data being in the image, ie. no additional formatted tracks filled with &E5
Any non standard format wouldn't emulate correctly...

Re: STH Elite disc image

Posted: Wed Sep 11, 2019 7:15 pm
by Diminished
That explains it, thanks.

Was Elite not available at all on 40 track disc?

Re: STH Elite disc image

Posted: Wed Sep 11, 2019 7:26 pm
by billcarr2005
On the original disc, drive 0 was 40 track and if an 80 track drive was detected the data was loaded from drive 2

Re: STH Elite disc image

Posted: Wed Sep 11, 2019 7:42 pm
by Diminished
So side A was 40 track and B was 80 track?

Does anyone know if there's an image of the 40 track version anywhere? Both my drives are 40.

Re: STH Elite disc image

Posted: Wed Sep 11, 2019 9:22 pm
by billcarr2005
The original disc has an unformatted track and also several tracks where the physical and logical track numbers don't match, so a straightforward SSD isn't possible... but there shouldn't be any reason why the STH version won't write to a 40 track disc, just delete $.ELTDEMO and $.ELTCODE (the ELITE rolling demo)

Re: STH Elite disc image

Posted: Wed Sep 11, 2019 10:22 pm
by Diminished
Ah, that's interesting. In theory I could write a nonstandard disc like that, but I'd need to write a parser for hq-UEF files and since I'm doing everything on an embedded system in ARMv4 ASM with a 16K RAM workspace, I don't fancy it right now.

I'm slowly finding more discs that don't have a 40-track compatible version on STH. Repton 1 is another one.

Re: STH Elite disc image

Posted: Thu Sep 12, 2019 8:11 am
by billcarr2005
Diminished wrote:
Wed Sep 11, 2019 10:22 pm
I'm slowly finding more discs that don't have a 40-track compatible version on STH. Repton 1 is another one.
But at least Repton ( the version here? https://www.stairwaytohell.com/bbc/arch ... Repton.zip ) is undersized and can be padded out if necessary. The fact that the SSD says it's an 80 track disc can largely be ignored.

Re: STH Elite disc image

Posted: Thu Sep 12, 2019 12:25 pm
by Diminished
billcarr2005 wrote:
Thu Sep 12, 2019 8:11 am
But at least Repton ( the version here? https://www.stairwaytohell.com/bbc/arch ... Repton.zip ) is undersized and can be padded out if necessary. The fact that the SSD says it's an 80 track disc can largely be ignored.
Whoops, you're right.

Well, that's curious; my code rejected that image. It seems you have just managed to find a bug from miles away. :lol: