[Coladam] Delete a backup file on DDP

Rich Drushel drushel at apk.net
Thu Jan 28 20:26:37 CET 2010


On Thu, January 28, 2010 10:02 am, geoff at oltmansfamily.org wrote:

> For example if I attempt to use clone21 from TDOS and write a disk image to
> a blank disk, it's not writing the blocks in the right locations. ADAM 160k
> disk images are interleaved 5:1 (or is it 1:5?), so disk sectors aren't
> stored sequentially. The code in ADAMEm does this calculation properly, but
> when I look at the resulting image in a hex editor, things aren't correct.
> For example, the first write that clone does should be to block 0, which
> should also be offset 0 in the resultant disk image file. In my case
> though, it is several kb past the beginning of the file.

     Here are the interleave data from the floppy I/O routines in
ADAMserve (pasted right from DATA_31x.ASM).  Each entry is a table;
offsets into the table return low-level info to map ADAM 1024-byte
"blocks" into two IBM 512-byte "sectors", including "head" info (i.e.,
which side of the disk you are reading for double-sided media).  5.25"
double-sided disks map differently than 3.25" double-sided disks:  320K
disks put the first blocks 0-159 on one side (for compatibility with 160K
single-sided disks) and 160-319 on the other.  3.25" media switch sides
after every "track" (group of sectors in a cylinder) of data.  160K/320K
disks have 8 sectors per track; 720K disks have 9 sectors per track;
1200K disks (no native ADAMnet drives, but possible with ADAMserve)
have 15 sectors per track; and 1440K disks have 18 sectors per track.
All disks have 40 tracks.  Remember that 2 sectors = 1 block.  I am
omitting here the math to actually map an ADAM block to a given IBM
head/track/sector pair for a given drive size, but can provide it if
there is interest.

offset_160_320  DB       1,6, 3,8, 5,2, 7,4
;
offset_720      DB       0,1, 0,5, 0,9, 0,4, 0,8, 0,3, 0,7, 0,2, 0,6
                DB       1,1, 1,5, 1,9, 1,4, 1,8, 1,3, 1,7, 1,2, 1,6
;
offset_1200     DB       0, 1, 0, 5, 0, 9
                DB       0,13, 0, 2, 0, 6
                DB       0,10, 0,14, 0, 3
                DB       0, 7, 0,11, 0,15
                DB       0, 4, 0, 8, 0,12
                DB       1, 1, 1, 5, 1, 9
                DB       1,13, 1, 2, 1, 6
                DB       1,10, 1,14, 1, 3
                DB       1, 7, 1,11, 1,15
                DB       1, 4, 1, 8, 1,12
;
offset_1440     DB       0, 1, 0, 5, 0, 9, 0,13, 0,17, 0, 3
                DB       0, 7, 0,11, 0,15, 0, 2, 0, 6, 0,10
                DB       0,14, 0,18, 0, 4, 0, 8, 0,12, 0,16
                DB       1, 1, 1, 5, 1, 9, 1,13, 1,17, 1, 3
                DB       1, 7, 1,11, 1,15, 1, 2, 1, 6, 1,10
                DB       1,14, 1,18, 1, 4, 1, 8, 1,12, 1,16


    *Dr.D*

-- 
Richard F. Drushel, Ph.D.            | "They fell:  for Heaven to them no hope
Department of Biology                |  imparts / Who hear not for the beating
Case Western Reserve University      |  of their hearts."
Cleveland, Ohio  44106-7080  U.S.A.  |         -- Edgar Allan Poe, "Al-Aaraaf"




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