8 May
2001
8 May
'01
6:59 a.m.
On Tue, 8 May 2001, Stan Barr wrote:
According to an old Peter Norton book, Dos 2.1 only
supported 320(!)
and 360K disks.
There are a lot of people on this list who know a lot about disk
formats. Quoting Norton about disk formats is like quoting billg about
Apple computers.
[BTW, on the Computer Bowl, nither billg nor anyone else on his team knew
where the write protect notch is on an 8" diskette!]
[BTW, Peter Norton has written a bunch of stuff where he refers to DOS
interrrupt vectors by their decimal numbers ("Int 33")]
PC-DOS 2.10 (NOTE there are TWO digits after the period) supported 160K,
180K, 320K, and 360K. Even Peter's own fUtilities supported the SS (160K
and 180K) formats.
Support for 720 and 1200K came with DOS3.
Support for 720K came with MOST versions of MS-DOS 2.11, but not until
3.20 for PC-DOS.
There doesn't exist a PC-DOS 2.11, only MS-DOS.
Support for 1200K (aka "1.2M") came with 3.0
Support for "1.4M" came with 3.30
XTs had to use a separate device driver for the higher
densities.
It takes different HARDWARE, NOT JUST DRIVER, to do higher density, such
as 1.2M or 1.4M formats.
Fortunately, 720K is NOT a higher density. The physical format on each
track is the same as 360K; but there are 80 cylinders instead of 40, and
some software parameters are different for the directory.
With added software, ANY version of DOS can do 720K. But with certain
OEM's MS-DOS 2.11 and with PC-DOS 3.20, XTs are quite happy with 720K.
Actually, it is EASIER to use "other" formats with an XT than an AT, since
an XT doesn't store CMOS info about drive types and/or CARE what kind of
drives are connected.
To use 720K and PC-DOS 3.20 with an XT with an IBM BIOS required using
DRIVER.SYS. To use 720K and PC-DOS 3.20 with a non-IBM BIOS could be done
with DRIVPARM (sets parameters without loading a device driver), which was
present on both MS-DOS and PC-DOS, but undocumented in PC-DOS.
--
Grumpy Ol' Fred cisin(a)xenosoft.com