Reverse-engineering WD1000, WD1001 hard disk controllers

Kip Koon computerdoc at
Sun Nov 20 00:21:57 CST 2016

Hi Eric,
Thank you for the information and correction.  I was going entirely from memory obviously.  :)  That project was approximately 37 years ago!  Now I want to find that old controller so I can see what the correct model is.  I'll know it right away since it has my eprom on it.  I'll let you know what the card number is when I find it.  I'm going to be working out there in the next few days anyway.  This should prove to be fun.  

Kip Koon
computerdoc at

> -----Original Message-----
> From: cctalk [mailto:cctalk-bounces at] On Behalf Of Eric Smith
> Sent: Sunday, November 20, 2016 12:20 AM
> To: General Discussion: On-Topic and Off-Topic Posts
> Subject: Re: Reverse-engineering WD1000, WD1001 hard disk controllers
> On Sat, Nov 19, 2016 at 6:20 PM, Kip Koon <computerdoc at> wrote:
> > When you have a stable version, please let me know.
> I'll try to remember to post an update here.
>   I would be interested in seeing the disassembled source code for the
> > WD1000 8-bit card I modified years ago.
> > I had an MFM hard drive or two that I was trying to format, but the 4 sets
> > of hard drive parameters offered by the WD1000 didn't match one of my hard
> > drives so I replaced one of the sets of hard drive parameters by reading
> > the eprom using my homebrew eprom burner setup I built for my Color
> > Computer 1 F Board version way back when I was in my 20s.
> >
> The WD1000 itself doesn't store any hard drive parameters. It just assumes
> that the host knows the correct ranges of cylinders heads, and sectors to
> use. I think the EPROM you describe that has stored drive parameters must
> be have been a firmware BIOS EPROM that was executed by the host system.
> It's possible that some variation of the WD1000, e.g., for ISA bus, had
> such a thing, but I've only concerned myself with the firmware that
> actually runs on the 8X300 processor on the WD1000, so nothing I'm doing
> will help in any way with an EPROM as you describe.
> I did design and wire-wrap a WD1000 to Color Computer 2 interface back in
> the day, and wrote an OS/9 driver for it, though I never wrote any boot ROM
> for it, so I had to boot from floppy.
> > After reinstalling the WD1000 back into the computer, the WD1000 came
> > right up and asked for my choice to pick for the hard drive parameters to
> > use to format the hard drive with!  It even included the set of hard drive
> > parameters I had put into the eprom!  I was very proud of what I had
> > accomplished!
> >
> Rightfully so. I've done a lot of firmware hacking over the years, but I
> never needed to do it to change disk geometry.  It really sucked that so
> many controllers had only hard-coded choices in their BIOS ROMs; thankfully
> by the 1990s almost all of them were configurable.

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