salfter/fluxengine
1
0
Fork 0
mirror of https://github.com/davidgiven/fluxengine.git synced 2025-10-31 11:17:01 -07:00
Code Issues Packages Projects Releases Wiki Activity

No, wait. The AES Lanier sectors are clearly 256 bytes, but include the sector

Browse Source 
header.
This commit is contained in:
David Given
2019-03-03 12:43:18 +01:00
parent 3d72e79969
commit 654f250341
3 changed files with 9 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
doc/aeslanier.md
View File

@@ -11,13 +11,15 @@ of nearly £50,000 in 2018!).
processing software off twin 5.25" drive units, but apparently other software
was available.
The disk format is exceptionally weird. They used hard sectored disks, where
there were multiple index holes, one for each sector. The encoding scheme
The disk format is exceptionally weird. They used 77 track, 32 sector, single
sided _hard_ sectored disks, where there were multiple index holes,
indicating to the hardware where the sectors start. The encoding scheme
itself is [MMFM (aka
M2FM)](http://www.retrotechnology.com/herbs_stuff/m2fm.html), an early
attempt at double-density disk encoding which rapidly got obsoleted by the
simpler MFM. Even aside from the encoding, the format on disk was strange;
unified sector header/data records, and 253 (or maybe 252) byte sectors.
unified sector header/data records, so that the sector header (containing the
sector and track number) is actually inside the user data.
FluxEngine can read these, but I only have a single, fairly poor example of a
disk image, and I've had to make a lot of guesses as to the sector format