21 Apr
2000
21 Apr
'00
4:45 p.m.
"Fred Cisin (XenoSoft)" <cisin(a)xenosoft.com> wrote:
On Fri, 21 Apr 2000, Dwight Elvey wrote:
Hi Fred
I hadn't thought this through. I just assumed that since DOS
has two copies of the FAT that it would stretch past the area
that CP/M usually uses. I guess that Sam needs some way to
look at raw sectors. I don't think we can assume anything other
than it looks like he can at least read the directory area.
Although there are not as many basic tools for CP/M-86 as
were made for CP/M 2.2, I'm sure someone had a sector viewer
program. My gut feeling is that the disk have no data on
them and were either accidentally formatted or no data was
originally copied to them.
From what you say, it is still possible that they might have
a DOS format. If one can extract the FAT, the data can be found.
Of course the DOS directory would tie it all together.
Dwight
. . . I don't think is is a MS-DOS disk
either. The FAT and such take up a lot of space and
surely wouldn't return "NO FILE" if CP/M tried to read it.
In THIS case, I take it back, but because the NEC 8" CP/M disks that I've
seen used 256 bytes per sctor.
Although the FAT and such take up a lot of space, it's not THAT much, and
CP/M skips some tracks. A typical 8" (or 1.2M 5.25") MS-DOS uses 1/2K for
the boot sector, 2 copies of the FAT at 3.5K each, and 7K for the
DIRectory sectors. That is all done with by the end of the second side of
the first cylinder (#0). On double density CP/M 8", the directory hardly
ever starts before the first side of the second (#1) cylinder. Plus, the
latter parts (unused if the disk isn't full) of the MS-DOS DIRectory
sectors could be misinterpreted by CP/M as an empty directory.
Therefore, it's possible (although somewhat demented - BTDT) to actually
have two different DIRectory structures that access the same files in
order to create a distribution disk that is readable by multiple OS's!