Help needed identifying old MFM drives from the excavation

[Warner Losh]

On Sun, Dec 6, 2020 at 7:51 PM Fred Cisin via cctalk <cctalk at classiccmp.org>
wrote:

> On Sun, 6 Dec 2020, Chris Zach via cctalk wrote:
> > As the excavation of Bob's junkpile continues I have finally hit the MFM
> > layer. Specifically about 10 5.25 hard disks that look to be old style
> MFM
> > drives.
> > Vertex V150
> > Miniscribe 6085
> > ST 4038M Seagate Franklin telecom AT-40
> > Miniscribe 3650 HH
> > Seagate ST4096
> > Priam ID45-H
> > Rodime RO203E
> > RD54
> > Real ST506
> > Pair of ST412's.
>
> The Seagates were commodity drives, used in almost everything.
> Number is approximately the unformatted capacity.
> ST506 was 5MB formatted (305 Cyl x 2 heads) ;
> ST412 added buffered seek, was 10MB formatted (306 cyl x 4 heads).
> ST4096 was 80MB formatted.  (1024 Cyl x 9 heads)  For a long time, it was
> the most common of the largest drives in that form factor.  I found out
> that 135W XT/AT power supplies were not always happy trying to run two of
> those at a time.
>
> XT/AT MFM had 17sectors per track; 512 bytes per sector.
>
> Drives formatted on a machine other than 5160/5170 are likely to be
> unreadable with 5160/5170.
> Drives formatted for a given XT controller were often incompatible with
> another XT controller.  (Was some of that due to numbering sectors from 0
> Vs from 1?)
> Drives formatted with an AT controller were normally usable on another AT
> controller.
>

The mfm emulator at https://www.pdp8.net/mfm/mfm.shtml by David Gesswein
will read them all, though...

Warner