RE: MFM drive gone nuts

From: Martin Hoffmann-Vetter <>
Date: Sun, 20 Jul 2014 17:22:30 +0200
Message-ID: <003a01cfa42e$6cddcd80$>

>> The D9060/9090 used 256 byte Sectors,
>> so it's possible the C900 did too. The IBM PC XT/AT controllers used
>> 512Bytes 
>> per sector, so that's a likely showstopper right there.
> The C900 uses 512 byte sectors on the floppy, and the documentation
> says that it was done to match the hard disk. So I presume that the
> hard disk uses 512-byte sectors too.

The coherent use 512 bytes per sector, too. So this must be a 512 bytes sector format.

> The controller itself is labeled WD1003-CMD. I wasn't able to find any
> information on the Internet on it, but a Google search shows that
> there were cards for PC labeled WD1003-xxx where xxx was some letter
> and number combination.

Yes the WD1003 was a standard controller. There exists many variant of this controllers.

> So it looks probable that this controller
> uses the same format as these PC cards?

I think it too. There must be the same controller chip (wd11c00) on all these wd1003 (16 bit) controllers. But they have tolerances. So you can't read and write every harddisk with every WD1003 controller! But you have a good chance for read only!

> One other idea came to my mind: The controller has a 8749 CPU. It
> might be possible that this CPU died? Then obviously the controller
> would simply not respond to any commands from the computer in timely
> fashion, so the computer would think it's a timeout?

No, this cpu runs the factory test, too. This random seek was running and so the cpu must work.

Try to check the drivers and the pull ups on all control signals (34 pin connector)! Most of them are low active! All are open collector!


       Message was sent through the cbm-hackers mailing list
Received on 2014-07-20 16:00:33

Archive generated by hypermail 2.2.0.