ROM dumps of Intel MDS-2 IOC

Adrian Stoness tdk.knight at
Sun May 17 20:39:48 CDT 2015

wish i coud get mine to work when ever i put the cpu board in the screen
goes all weird

On Sun, May 17, 2015 at 8:34 PM, Eric Smith <spacewar at> wrote:

> On Sun, May 17, 2015 at 6:06 PM, Dave Mabry <dmabry at> wrote:
> > As for the firmware, there were many versions.  At one point Intel
> released
> > an upgrade package called the iMDX-511.  That added cursor-addressbility
> on
> > the integral CRT, a function key on the keyboard (replaced the RPT
> (repeat)
> > key), some shortcut key sequences, improved speed, and other things I
> can't
> > remember.  It was a standard part of the Series-II at some point, about
> the
> > same time the white one became available.
> I've dumped all the programmable parts from a Series II with an IPB
> (8080 main CPU board) and the IOC iMDX-511 firmware, except the IOC
> 8041A and a few soldered-in bipolar PROMs used for address decode on
> the IPB.  My firmware images are on Bitsavers:
> > I have all that rom code.  I even took a swipe at disassembling it to
> try to
> > understand it.  That was never finished, but I did make some progress.
> As have I.  I found that the IOC firmware has undocumented 0dh and 0eh
> commands. Command 0x0d allows the main CPU to write to arbitrary IOC
> memory, and is probably for diagnostics, but is not allowed unless IOC
> RAM location 5af4h contains the value 24h, and I haven't figured out
> how that can be made to happen, since you can't use command 0x0d to
> set it if it isn't already set.  I haven't yet figured out what
> command 0eh does.
> > If the 8741/8041 chip on the IOC was called the PIO (Parallel I/O) then I
> > have that rom code too.  I have a document that says the 8041 is indeed
> the
> > PIO.
> Yes. I'd like a copy. Can you confirm that the one you dumped is P/N
> 104566-001?
> > The iMDX-511 also included an enhancement to the keyboard processor.  I
> have
> > that rom code as well.
> 104675-001, included in the ZIP file on bitsavers.
> Do you have dumps of the firmware for the RPB86 and/or RPC86 8086 CPU
> boards used in the Series III?
> Best regards,
> Eric

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