Simon Cooke wrote:
That one basically ignored the track/sector addresses (wrote them out as weird values IIRC), so you'd need to manage all that manually to get the data off the disk.
The one I have is 5x1024 per track, with the cylinder value as 128 in each header, except for the boot sector and first directory sector that need to be correct. The head value matches the physical location, though (unlike the PC) the WD1772 doesn't match the head value so it wouldn't have added to the protection anyway.
Here's a dump of the start of the disk: [Parallax.dsk] 2 sides, 82 tracks: 250Kbps MFM, 5 sectors, 1024 bytes, cyl=128: 0:0 1[c0,n2] 4 2 5 3 1:0 1 4 2 5 3 2:0 1 4 2 5 3 3:0 1 4 2 5 3 4:0 1[c4] 4 2 5 3 5:0 1 4 2 5 3
Hackier still was the lemmings one - same idea, but stuffed a lot more data in there. Can't remember how, but I think it was 5.5k/track
It was indeed 5.5K - 5x1024 + 1x512 per track, interleaved probably due to the small inter-sector gap, and skewed for a slight speed gain:
[Lemmings.dsk] 2 sides, 82 tracks: 250Kbps MFM, 2 sectors, 512 bytes: 0:0 1 2 250Kbps MFM, 6 sectors, 1024 bytes: 1:0 5 3 6 4 1[n2] 2 2:0 3 6 4 1[n2] 2 5 3:0 6 4 1[n2] 2 5 3 4:0 4 1[n2] 2 5 3 6 5:0 1[n2] 2 5 3 6 4
Even hackier was one that I never used, but would put dupes of sectors on each track. Unless you synced up to the spindle marker, you'd have a 50/50 chance of getting bogus data.
That trick is used by a few +3 disk titles, including Tomahawk. They only appear to be there to choke copiers though, as I couldn't see any sign of them being checked by the protection.
Si
