2.8M Floppy (Was: thinking of the "ultimate" retro x86 PCs -

Fred Cisin cisin at xenosoft.com
Thu Jun 2 19:09:38 CDT 2016

I hope that Chuck will correct some of the errors that I made below:

On Thu, 2 Jun 2016, Chuck Guzis wrote:
> Not sure about the need for drivers, however.  I guess it depends upon
> the type and version of your OS.  I never had the need of them.  Simply
> declaring the drive as such in the BIOS setup was sufficient.

No need for drivers IFF your hardware (FDC and BIOS) and OS were new 
enough.  I think that SOME FDC boards that supported 2.8M data transfer 
rates had BIOS chip to "update" the system BIOS.  If not, DRIVER.SYS or 
DRIVPARM=.  If the OS was too old to know that drive format (<4.00?), then 
it called for a relatively simple block mode device driver.
Remember that PC/MS-DOS
1.00 supported 160K
1.10/1.25 supported 320K
2.00 supported 360K (and 180K)
2.10 tolerated slow Qumetrak 142
2.11 (MS-DOS) was OEM'd, and LOTS of OEMs added other DOS formats 
(including 3.5")
3.10 was first to support CD-ROM (MSCDEX and [undocumented] network 
3.20 added 720K  (first PC-DOS to support 3.5")
3.30 added 1.4M
Was it 4.00 that added 2.8M?

Those drives could, of course, be used on previous OS versions with device 

On MS-DOS 2.11 and 3.31, always look for which OEM it was from!  MODE.COM 
sometimes handled different videos (internal/external on portables!), and 
OEM versions handled any special floppies.  For example, Gavilan 2.11 was 
SS 3.5", 2.11J and above were DS (but NOT same format as PC-DOS 3.20), 
IIRC 2.11K brought it into line with PC-DOS 3.20.
And, for example, early HP 3.5" was not the same format as PC-DOS.

DRIVER.SYS permitted using formats that were newer than the SETUP program 
knew about, such as 720K 3.5" on 5150 and 5160, or pre 3.5" 5170.
DRIVER.SYS created an additional drive letter, so the 3.5" drive would end 
up as drive D:

DRIVPARM changed the specs of the drive without creating a new letter, so 
your 3.5" could still be B:
DRIVPARM was undocumented in PC-DOS 3.20 and 3.30, but it WAS there, and 
worked just fine with generic BIOS.
BUT, I was surprised to find it FAILING with real IBM BIOS (or image 
thereof) in the same machine!   Good reason to leave it out of the manual!

Both DRIVER.SYS and DRIVPARM= used format #9 for 2.8M
0 = 360K
1 = 1.2M
2 = 720K
3 = 8"SD
4 = 8"DD
7 = 1.4M
9 = 2.8M

You could also specify drive type using T:x/N:y (tracks and sectors), but 
disappointingly, it only used those to identify which one of the ones in 
its table; you could NOT use that to specify a 35 track or 70 track drive.

BTW, if you had four floppies installed, and the BIOS understood, then 
your floppies would be drives A:. B:, C:, and D:. and you hard drive would 
be drive E:.  But some programs were "hard-wired" to assume C: as the hard 
drive, including the INSTALL for MS-DOS 5.00! MICROS~1's answer: "Install 
it on drive C:, and then copy it to the hard drive that you want it on." 
I refused to install it to a 3" disk, so I installed on a different 
machine, and created a 360K boot disk, plus copied all of the other files 
to a sub-directory on the hard disk (E:).

Grumpy Ol' Fred     		cisin at xenosoft.com

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