Re: MFM drive gone nuts

On 23/07/2014 12:25 PM, smf wrote:
>> Not quite; we're talking about the same computers, interface and file 
>> systems.
>
> The MFM controller card has a CPU and it's own proprietary software, 
> making it just as important as your motherboard and filesystem.
> How the MFM controller works isn't part of the ISA or ST506 standard, 
> the same as the format and the filesystem of a floppy disk isn't part 
> of shuggart.
>
> The only way to fix the problem would have been to force all MFM 
> controller cards to work the same way.
>
>> That was probably the best thing about IDE; it combined the 
>> controller and drive in one package with a common logical interface;
>
> You still have the same problem if the controller card on the IDE 
> drive dies. It's worse as there is no guarantee the interface is the 
> same and the controller firmware is on the drive.

The controller boards between the same model drive are interchangeable 
and that has been done since forever where the controller board on the 
IDE drive has failed and the data has to be retrieved.
The IDE interface itself is pretty dumb and universal. As long as you 
know the parameters for the articular IDE drive that you enter in the 
PC'  BIOS (or more commonly autodetect) you can access and read the 
drive contents


> Unless the firmware on the drive is compatible with the controller you 
> have fitted then you won't get anything working unless you have access 
> to the tools used to load the firmware in the factory (which is 
> generally unlikely).
>
>

As long as the controller board on the actual drive is from the same 
model you can swap it. The IDE interfacer on the mainboard or card is 
universal.

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.

There may have been some minor issues, and exceptions with sectors 
marked as bad - but in terms of retrieving data that wasn't much of a 
problem.





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