23 Jan
2008
23 Jan
'08
4:49 p.m.
On Wed, Jan 23, 2008 at 09:25:16PM +0000, Peter Hicks wrote:
Hello!
I have an elderly Mitsubishi MR535R (60Mb-ish RLL) connected to an ST11R
controller. The control and data cables are homebrew although neatly and
tidying put together.
When I power up an old Pentium II - because it's the only box I have with
ISA slots - the ST11R pops up a message on the screen, clunks the drive in
an "I'm accessing you" kinda way, but then reports "No drives
found" and
continues merrily on its way.
I have never tried an MFM drive on a machine newer than about a 386. No
idea if the Pentium-II chipset or its BIOS could be adding to your troubles
or not.
As my knowledge is a tad rusty, can anyone help
identify what the problem
here is? BIOS shadowing is off for the memory locations that are, and
could, be used by the card.
Good.
The only thing I can think of is that the ST11R is in
fact an ST11M, tries
to read the drive, goes "Uh-oh, don't recognise you" and reports "No
drive
found".
So you are saying that this drive wasn't originally used with this
controller? If that's the case, then you need to ensure that the drive
is formatted for an ST11R. Even if the drive happens to be rated for MFM
vs RLL (an ST-255 vs ST-238R, say), the controller will _try_ to format
the drive. You just might have problems with completing the format with
few enough errored sectors or with long-term use. The controller doesn't
know anything about the drive that you don't tell it during formatting
(well... if you tell it that you have 8 heads, it *will* notice that there
are only, say, 6... but not the other way around).
I don't have access to the 'net at the moment (for another 12 hours), so I
can't look up the ST11R, but if you find docs, there should be formatting
instructions. From memory, a common way to do it was to jump into DEBUG
and call the formatter in ROM with something like 'G C800:5'. Some
controllers did not have ROM formatters - they came on a floppy. The
docs will sort all of that out.
I don't think the BIOS will see an unformatted MFM/RLL drive on the end
of a controller, or at best, you'll get a cryptic numerical error like
"1701 drive error". It all depends on how new the BIOS on the controller
is. Adaptec SCSI cards were, IMO, one of the better products for showing
you meaningful errors and for the quality of their ROM-based formatter.
MFM and RLL controllers were beyond terse.
Unfortunately I lack an MFM hard drive to test this
out with :(
You can format an RLL drive as MFM. Back in the day, it wasn't
commonly done because of the 25%-40% cost differential (RLL drives
were cheaper per byte than MFM, but not all that much). Formatting
an MFM drive as RLL was always a crap shoot, but the controller _will_
give it a shot.
-ethan
--
Ethan Dicks, A-333-S Current South Pole Weather at 23-Jan-2008 at 21:40 Z
South Pole Station
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Ethan.Dicks at usap.gov http://penguincentral.com/penguincentral.html