formatting MFM drives on a IBM PC

allison allisonportable at
Wed Sep 27 11:16:48 CDT 2017

On 9/27/17 10:59 AM, Ethan via cctalk wrote:
>> IIRC, the first time I had problems with the low level format was 
>> with one
>> of the early IDE controllers and a 230MB Maxtor. Crapped out the entire
>> firmware, was never able to get it to admit who it was again. Seemed to
>> work okay with earlier MFM/RLL 40 MB and 80 MB Conner drives (I 
>> think, it's
>> been a while).
> AFAIK a lot of IDE drives store part of the firmware on the spinning 
> disk in a special section of the disk. Not sure if those early models 
> used that trick to cut costs or not?

Not so for MFM.  All and IDE drive is in essence is a MFM with a WD1003 
controller as IDE is the buss
level view of the 1003 (or the later 1005 RLL encoded version).

> The idea of IDE, as my understanding, is the controller that existed 
> as an ISA card was moved onto the actual drive, and then what became 
> the controller was mostly just extending the ISA bus over to the drive.
> My first hard drive was a SCSI-1 ?Fuji? on a Seagate 8-bit ISA card. 
> Families Tandy 1000sx. I remember in the end playing with low level 
> formatting tools and interleves, then the drive dying at the same 
> time. I correlated the two together then, but looking back I think the 
> issue was drive motor/bearings/stuck rotation of platters.
My first drive was a ST506 on S100 using the Teltek controller (CP/M) I 
was an early adopter and
5MB felt like a a lot of space when floppies were maybe 720K (2side 
double density 80track) back
in 1980.  After that it included over time St506, st412(RD50), RD51(also 
sold as MFM for PCs 31mb) then SA225(RD31), sa250 (RD32), Quantum D540 
(RD52) and a long list of others including most of the drives to 150mb.  
Those larger than 30mb woere used in my QBUS PDP11's and MicroVAX 
systems.  Least that was
true up to about 93ish when I started using PCs (XT class running 

DEC for MFM RDxx disks had different formats depending on system those 
being Rainbow, PRO, QBUS(RQDX1,2 or RQDX3) which was PDP11 and MicroVAX( 
MV2000 and QBUS).  That's for Low level format.  FOr High level
format for the different file systems were handled by the OS.  While 
they were sometimes called format it was really writing a bland initial 
filesstem on formatted media.

IDE disks format usually meant high level only.  SCSI could be either 
depnding on the specific controller and media.

PCs forced the issue with multiple controlled not all the same  For 
example the ST225 could be formatted
with WD1003(plain MFM) or WD1005 (RLL encoded).  There were many versions.

In the CP/M s100 days you had teltek, Konan and many others all 
different.  Media must be formatted for the controller and there was 
code supplied for that. Those were the bus installed controller as 
Xyebc, WD, Adaptec also had host controllers as well as SASI/SCSI 
interfaced versions to drive MFM drives.

The whole of that is 5.25 disks and the later 3.5inch IDE class 
devices.  Other formats were well, different.


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