Date   : Sat, 11 Nov 2006 22:37:17 -0000
From   : dl.harper@... (David Harper)
Subject: 5 1/4" disc on PC

Bill Keesing wrote in response to BRAHMS:

>> As part of my recent efforts to get software accross to my master and
>> beebs I tried connecting a 5 1/4" disc to my PC - this did not work:
>>
>> 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
>> just made squeaky noises instead of the heads moving.
>>
>> My bios had no other settings - is it a lost cause?

> This is because the floppy controller in the modern PC cannot read the
> low density disks.

I am not convinced it has anything to do with this (despite the other debate 
that is going on at the moment).

It sounds to me like a stepping-speed problem. A 5.25" drive cannot be brand 
new :-) and it might be that the stepper motor that moves the head cannot 
cope with the speed it is being asked to move by the more modern BIOS.

I do not know Omniflop well, and do not know whether this is an adjustment 
that can be made within it. If it is, then it would be worth trying.

You probably won't be able to adjust the stepping speed from the BIOS 
settings in the CMOS - PCs are just not that flexible.

> If you can get hold of an older PC, possible one with an FDC that is a
> plugin board then that will be able to cope.

I would agree that you should try it on an older PC (and if it won't work on 
an old one, then throw it!) But if it will work on an old one, then I 
suspect it is a BIOS rather than an FDC problem.

David Harper