Re: MFM drive gone nuts

From: Clockmeister <>
Date: Wed, 23 Jul 2014 19:12:45 +0800
Message-ID: <>
On 23/07/2014 4:34 PM, smf wrote:
>> As long as the controller board on the actual drive is from the same 
>> model you can swap it.
> Sure, the original point was with separate boards that you were forced 
> to replace controller boards with the same one or you wouldn't be able 
> to access the existing contents & to use the drive you'd have to low 
> level format it and start again. My point about IDE is you have the 
> same problem, except you can't always just low level format it and 
> start again because the controller firmware is on the drive.
>> The only problems where with the early PC's where you could only 
>> select from a select amount of definitions (and couldn't enter your 
>> own to suit the drive, or autodetect), but that's a seperate issue 
>> entirely. If a drive worked with one of those systems but the logic 
>> board on the drive died, you could certainly replace the logic board 
>> from another drive and you could retrieve the data.
> That isn't MikeS's experience and I'm pretty sure I've seen it happen 
> to. The last MFM controller I looked at documentation for stored the 
> drive geometry on track 0 during low level format, which I'm pretty 
> sure is controller specific. Even if the data tracks are stored in a 
> compatible way (which isn't a high chance) then I believe track 0 is 
> going to cause you issues.

When I said early PC's, I meant early PC's with fixed  IDE definitions 
in the BIOS. XT class machines didn't store drive definitions in BIOS, 
that was the job of the controller.

I have retrieved data from MFM/RLL drives using random controllers 
simply because the controller had a drive definition that was close 
enough, or supported the most common drives but it was hit and miss.

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Received on 2014-07-23 12:00:02

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