Date   : Sat, 18 Nov 2006 00:12:59 +0000
From   : jgh@... (Jonathan Graham Harston)
Subject: 5 1/4" disc on PC

>Message-ID: <000401c705e1$f1544240$0301a8c0@...>
 
"David Harper" <dl.harper@...> wrote:
> >> When the BIOS was set to 360k 51/4 disc the POST (floppy seek) failed
> >> and the drive only showed up as 40T in omniflop
> >> When BIOS set to 1.2M it passed POST, showed up ok in Omniflop but
> 
> It sounds to me like a stepping-speed problem. A 5.25" drive cannot be brand
 
There are different issues with 5.25" drives on PCs. A 40 track
5.25" "360K" PC drive rotates at 300rpm, whereas a 80 track 5.25"
"1.2M" PC drives rotates at 360rpm. "Proper" 80 track 5.25" drives
for BBCs rotate at 300rpm. Drives for BBCs were often 1.2M drives
with links or solder pads that could be set to make them rotate at
the correct 300rpm.
 
I'm doing this from memory at the moment, but with a PC you need
to trick it to use a 5.25"/80trk/300rpm drive correctly by telling
the BIOS that it's actually a 3.5" drive.
 
Though, for software that bypasses the BIOS this should be
irrelavtnt.
 
-- 
J.G.Harston - jgh@...                - mdfs.net/User/JGH
Sheffield Boundary Review at http://mdfs.net/User/JGH/Docs/Politics/ParlReview