Working 8" Floppy drives??? (from originator)

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Fri May 9 18:34:00 2003

> ? Re: Working 8" Floppy drives??? (Fred Cisin)
> from yesterday's digest?
>
> Fred asks if we have considered substituting 1.2M 5.25"
> drives. Hmmmm. I didn't know there were such drives.
> I know of DSDD 360K 5.25 drives and 1.44M 3.5 drives,
> even 720K 5.25 drives, but not 1.2M 5.25 drives.

Oh yes, the 1.2M drive (that's 1.2 'IBM Megabytes' -- 1000*1024 bytes)
was a common drive on PC/AT (286) and later PCs. The PC I am typing this
on has one fitted.

It's a double-sided 80 cylinder unit turning at 360 rpm (like an 8"
drive, all other 5.25" and most 3.5" [1] drives turn at 300 rpm). It uses
the higher data rate (500kbps) like an 8" drive.

I have successfully used such a drive in place of an 8" drive. It's not a
drop-in replacement -- the cable/connectors are different, and there are
minor differences in some of the signals. Btu it can noramlly be got to
work. The problems really start if the drive you're replaceing wasn't a
standard 8" drive (the cannoical example of this is the DEC RX01 or
RX02), or if it uses some of the features on the 8" drive (data
separator, hard sector sector/index hole separation) that were never
provided on 5.25" drives

[1] Early 3.5" drives, often used by HP, rotated at 600rpm. And for
completness, there was a 5.25" drive that rotated at 180 rpm, allowing
the use of 1.2M disks on a normal (not high density) controller.

>
> On the general subject of using a substitute drive. I
> have actually been considering if this could be done. I
> have not suggested doing that because I need to find out
> the feasibility. I would hope we could at least get into
> the 1990s with a 1.44M 3.5 in floppy drive.

It's possible, but if you want to go that route, get the machine working with
a 1.2M 5.25" drive first. Once that works correctly, then get it working
with the 3.5" unit. By doiing the conversion in 2 stages, you will have a
clearer idea as to where any problems are coming from.

[...]

> These replies will probably be helpful to someone with a
> hardware background (which I'm not). They point out the

I sometimes forget that not everybody was born holding a soldering iron
and screwdriver :-).. Although I do find it hard to understand how anyone
can attempt to maintain and/or modify a computer without understanding
some hardware (and for that matter some programming).

> 11. Re: Working 8" Floppy drives??? (Tony Duell)
>
> Your answer is not silly at all. I didn't know whether
> such drives would be very rare or plentiful in the
> "vintage" market. I see now that there are "plenty" of

They are not rare. I don't know how easy they are to find for sale --
certainly I am not selling any of mine. But there are plenty of working
drives still around (Even if most of them are attached to working vintage
computers).

> The client has been repairing the drives for years. They
> are in heavy constant use. I get the impression that
> they are simply getting too fragile to repair.

I find that very hard to believe. These drives were _very_ solidly made.
I supplse it's possible the heads have worn out with all that use, but
just about anything else can be fixed quite easily. Heads can be replaced
if you can find them, BTW....

-tony
Received on Fri May 09 2003 - 18:34:00 BST