ISA MFM disk controllers

Phill Harvey-Smith afra at
Sat Jun 20 07:26:02 CDT 2009

Christian Corti wrote:
> On Fri, 19 Jun 2009, Mr Ian Primus wrote:
>> Now, here's the dilemma. The stock card won't respond to the usual 
>> debug commands - they just freeze the computer. The original 20mb 3 1/2"
> Normal MFM controllers never come with an own BIOS, so there's nothing 
> to jump to.

Um that depends, the models the OP was discussing IIRC are XT controlers 
which *DO* for the most part come with their own BIOS, as the XT roms 
know nothing about hard disks of any sort.

However for 16 bit AT type controllers you are mostly correct, that they 
don't need a BIOS since the AT rom does know about hard disks.

There where exceptions however I have (or used to anyways) in my box of 
old cards a Seagate (I think) RLL controler that did have onboard bios, 
I believe for very old AT  type boards that didn't have CMOS settable 
drive parameters.



Phill Harvey-Smith, Programmer, Hardware hacker, and general eccentric !

"You can twist perceptions, but reality won't budge" -- Rush.

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