Need documentation - MFM controller

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NA...@rohvm1.rohmhaas.com

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Mar 16, 1993, 9:34:41 AM3/16/93
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Hi all. About a week ago I posted a note about my pc being unbootable
(C: and D: in conflict locked up in CMOS) Thanks to all who responded.
It only took 2 hours for cmos to lose its memory and then I was able to
get in and take care of the problem. Now that things are ok again, I have
the original problem. When I boot up I get D: drive error press F1 to
continue. I've checked all jumpers, drive selects, resistors, and other
configuration stuff. It all checks. Does anyone have any documentaion
on an SMS MFM controller. The board has several chips labelled OMTI on
it. There are at least 8 jumpers and there is also a prom which I'm not
sure how to access. I'd like to re-low-level format using the controller
and see if that would take care of it.

Thanks in advance.

R.v.Kampen

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Mar 22, 1993, 12:07:10 PM3/22/93
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In article <93075.09...@rohvm1.rohmhaas.com> NA...@rohvm1.rohmhaas.com writes:
>configuration stuff. It all checks. Does anyone have any documentaion
>on an SMS MFM controller. The board has several chips labelled OMTI on
>it. There are at least 8 jumpers and there is also a prom which I'm not
>sure how to access. I'd like to re-low-level format using the controller
>and see if that would take care of it.
>
>Thanks in advance.
what I figured out about most MFM controllers is:
4 jumpers/switches are used to select drive type,
these 4 don't necisarily correspond to the bits in an index of 0-15
in the table with drive types in the rom, but are mixed up a bit.

then on one of my controllers the other 4 jumpers select the
rom address (c800 or ca00), enable/disable rom
io address bits 3 and 2.

but not all is clear to me yet. If I low level format a hard disk
with one controller it is not always readable by another (both MFM).

willem

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