4 floppy disk drives on a PC?

From: Fred Cisin <cisin_at_xenosoft.com>
Date: Mon Jan 17 19:19:38 2005

On Mon, 17 Jan 2005, Eric Smith wrote:
> You don't really need a 3.5" 720K drive. Unlike the 360K/1.2M situation
> with 5.25-inch drives, the 1440K 3.5" drives can reliably read and write
> 720K diskettes.

The 1.4M does, indeed seem to reliably handle 720K.
The somewhat rare 67.5tpi 3.5" drive (Epson) might have the expected
issues of track width.

> IIRC, there was a driver supplied in some (but not all) versions of DOS
> called DRIVER.SYS which had to be installed using a "DEVICE=" command
> in CONFIG.SYS in order to support extra floppies. I don't recall whether
> it allowed specifying a base IO address for a secondary controller.
> They may have removed some functionality in later DOS releases.

DRIVER.SYS was included starting with PC-DOS and MS-DOS 3.20
(when IBM started supporting 720K 3.5")
A few OEM MS-DOS versions had similar drivers since 2.11
DRIVPARM was also included, but undocumented in PC-DOS, and not compatible
with the real IBM BIOS.

DRIVER.SYS does NOT include IO addresses, etc. It assumes that there is
already full BIOS support in INT 13h

Grumpy Ol' Fred     		cisin_at_xenosoft.com
Received on Mon Jan 17 2005 - 19:19:38 GMT

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