[rescue] Anybody remember MFM? (Durango Poppy II problem)

Walter Belgers walter+rescue at belgers.com
Tue Aug 5 12:09:40 CDT 2003

Mike Hebel wrote:
> > Now the problem: although the Micropolis 1325 71MB MFM drive spins up, 
> > I
> > cannot read/write it, I get an error on the first block. I do have the
> > correct /dev entry: the HD drive LED goes on. I tried inserting another
> > (21MB) MFM drive with the same problem.
> Inserting another drive probably won't work.  You might want to look at 
> some low-level formatting routines.  Some of the older cards you had to 
> use a command in DOS debug to get to the low-level routines:  c800:g    
> Depends entirely on the card.

The 21MB disc was DOS-formatted (with MS-DOS installed, I took it out of
a 80286). So I don't think low-level formatting would help (besides,
since I cannot boot DOS, also not from floppy, I have no way to perform
a low-level format). The system has no interactive BIOS AFAIK.

> > The drive is connected to a board from 'Molecular Systems' which has 3
> > connectors: 2 for the MFM drive and a 50 pin connector. I am hesitant 
> > to
> > try out if it's SCSI. Were combined MFM/SCSI cards normal in the old
> > days?
> Umm...not that I can recall but it _might_ be SCSI-1.  If it is you'll 
> probably not find a drive that will run on that connector.

Why not? SCSI-2 drives should work on a SCSI-1 controller?

> > Also, there are two potentiometers (is that English? variable 
> > resistors)
> > that are next to the MFM connectors. Would fiddling with those improve
> > my chances of getting this thing to work?
> Don't mess with those!  If you're having a problem _now_ then you could 
> very well put yourself totally out of the picture because you'll never 
> get them back into the original adjustment.  IIRC they had something to 
> do with sync.  Data or motor I can't recall but either way they aren't 
> easily adjusted properly without the original signal specs from the 
> board manufacturer.

Then again, these may cause the problem..

Walter Belgers         "Si hoc signum legere potes, operis boni in rebus
walter at belgers.com       Latinis alacribus et fructuosis potiri potes!" 

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