>January 1986, PC-DOS 3.20 supported 720K
3.5".
>Later in 1986, PC-DOS 3.30 supported 1.4M.
On Mon, 12 Dec 2005, Chuck Guzis
wrote:
The 720K 3.5" drive was introduced by IBM in 1986
as an option for the
standard PC-PC/AT product line. What I recall about the PS/2 was the
support for DSHD and DSED 3.5 diskettes. In fact, drivers had been
available earlier than PC-DOS 3.2 from third parties for 720K 3.5" drives.
Numerous machines came out with 3.5" drives using "customized" versions of
MS-DOS 2.11.
2.11 and 3.31 seem to be the primary versions of MS-DOS that were
customizable by OEMs.
The "official", "standardized" support of 3.5" 720K in 3.20 was
with use
of DRIVER.SYS and/or DRIVPARM. DRIVPARM was incompatible with IBM's BIOS,
and therefore was undocumented in PC-DOS.
--
Grumpy Ol' Fred cisin at
xenosoft.com