ISA MFM disk controllers (From 19Jun09)

[Robert]

Hello Ian,

IIRC, the debug commands worked with XT controllers. It seems that the debug commands will not work with the newer AT controllers that have their own BIOS.

Also, aren't you talking about 5 1/2" drives? I thought that the smaller 3 1/2 drives were IDE drives, not MFM.

Disclaimer: I might be wrong. Others might have better answers.

Regards,
Robert Greenstreet
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Message: 9
Date: Fri, 19 Jun 2009 19:40:05 -0700 (PDT)
From: Mr Ian Primus <ian_primus at yahoo.com>
Subject: ISA MFM disk controllers
To: cctalk at classiccmp.org
Message-ID: <21393.98126.qm at web52703.mail.re2.yahoo.com>
Content-Type: text/plain; charset=us-ascii


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

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.

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

Pointers?

-Ian