ISA MFM disk controllers

Paxton Hoag innfoclassics at
Tue Jun 23 18:23:23 CDT 2009

> Anyone remember the difference between the various Western Digital MFM disk controllers? I've got a few in front of me right now, and I'm trying to figure out which would be the best for this Compaq Portable 286.
> I've got the good ol' WD1002A-WX1, and what looks to be the bigger verison, the WD1002S-WX2,

WX-1 is 2 MFM hard drives only, WX-2 is hard drives plus two floppys.
My CSC Hard Drive manual says it is an 8 bit contoller for two hard
drives.  To format use G=C800:5  (Why  is that so familiar!!!)

>From the book the default jumpers on the WD 1002A-WX1 are
W3,W4-2 & 3, W6-2 & 3, W8-2 & 3, S1-8 (AT Mode)

>then another, even longer card, the one that came stock with the Compaq, the WD1015-PL03.

That doesn't show up in the book, but it was probably made for compaq.
The first card (WD1002A-WX1) should work. However the setup programs
were custom for Compaq. I don't think you can just use debug unless
you know Compaq codes.

> 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" Miniscribe hard drive is dead (won't even spin). I am going to replace it with a similar 3 1/2" form factor drive - the NEC D3142. (43mb! Woo!) I already got the drive formatted and working on the small WD1002A-WX1 card, but it's been a while since I worked with MFM controllers - and I seem to remember the WD1002S-WX2 being faster or something.

I think you will need the compaq set up disks. I still have a set but
not sure where they are. I might be able to locate them if you need me

> Also, I don't remember the calculations for optimum interleave, I used 3, since that was the default....

I think an interleave of 3 would be OK as it is an XT class
controller. But, as mentioned, Spinrite can optimize it for you. The
nec drive is an AT class drive at 28 ms. It should work fine.

> Pointers?
> -Ian

Paxton Hoag
Astoria, OR

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