IDE <-> MFM

[Phill Harvey-Smith]

Quoting Christian Corti <cc at informatik.uni-stuttgart.de>:
> That doesn't make sense. IDE stands for Integrated Drive Electronics,
> which means that the controller is located on the drive. Therefore IDE
> controller cards don't exist,

This is indeed true, an IDE drive just looks like a controler chip and  
is addressed that way.

>                                  and you can't bride IDE to an ST-412
> interface type drive.

I wouldn't say can't, but it is quite a challenge, your bridge board  
would need to interpret the analog signals from the MFM controler,  
re-assemble them back to digital, format them into IDE commands and  
pass them along to the IDE drive.
It would also need to read the IDE drive, and then generate the analog  
signals that the MFM card was expecting.

It's been done IIRC for floppy disks which also use MFM encoding,  
though probably at a lower data rate.

> And the (original) IDE controller is just a plain old WD1003 integrated
> on the drive PCB. "MFM" and "IDE" are register compatible, the
> programming is the same, otherwise you would need an extra extension
> BIOS for your IDE drives. And an IDE HBA can be built with just an
> address decoder and some drivers/receivers (usually 74LS245).

Yes but that requires modification/replacement of the controler of the  
machine, which of course may not be a PC, so the way the registers are  
addressed may also be unknown. Whilst asuming the bridge board idea  
could be implemented, as far as the computer is concerned it is  
talking to an MFM drive so it should just work.

Cheers,

Phill.

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