Intellec MDS questions

From: Joe R. <>
Date: Thu Feb 3 12:08:23 2005

At 12:35 PM 1/30/05 -0600, you wrote:
>Hey all,
>Thanks for all the background and help on the Altair project. I'll be
taking some pics of the pile for a 'before and after' set. Hopefully there
will be an after worth mentioning ;-)
>Now on to Intel / Intellec MDS systems. I've got one that is alternately
described as an MDS225 or and MDS800. IIRC, the dual-disk unit is marked
MDS800, (blue in color) and the main chassis is marked MDS225 (white in
color, has a monitor, kb, and a series of pushbuttons with LED indicators).

  It your unit has a CRT built in then it's a Series II or Series III
machine (aka MDS-2xx) PERIOD. They were built in both blue and white. See
my webpage at <> for more
information about the differences in the various models of the MDS-2xx.
FWIW the 225 is by far the most common of that series. MOST of that series
had one built-in disk drive but not all of them. The MDS-800 is a smaller
blue box and does not have a built-in CRT or disk drive. It MUST have a
terminal to use it.

  The external disk drives come in two styles. The older model will be
model DDS-2DS or something like that. They are mounted vertically in a blue
box. The box can hold two drives and almost allways have two drives even
though the second drive is optional. The newer style are the white boxs
with one or two drives mounted horizntially. Those are option 730 or 720
depending on weather you get the DD or SD controller. Again they're usually
found with two drives even though the second drive is optional. Even though
the DDS-2DS is older it is frequently found with MDS-2xx systems.

>Information on these units is pretty sparse on the web; multiple google
searches have yielded little more than years of manufacture, and some price
>One question that should amuse the more veteran members of classiccmp is
this: What exactly is meant by "Microcomputer Development System"?

  Early on, Intel referred to the microprocessor chips as Microcomputers.
Hence the term MDS. The MDS was used to write, compile, test, and edit the
software AND you could also get emulator pods for the MDS that allowed you
to replace the target system CPU with the pods. That allowed you to run the
SW from the target system or from the MDS and set breakpoints, examine
memory, CPU registers etc. The MDS was capable of doing everything needed
to develope both the hardware and software for microprocessor based
devices. They're not commonly seen but Intel also made "Trace" pods for the
MDS that acted like Logic Analyzers and let you trace any digital signal.

It's like that old joke about "Repairing Robots".. Are they referring to
the process of repairing a robot, or to robots that perform repairs?
>Is the MDS a system for developing microcomputers, or is it a
microcomputer that is used for other forms of hardware / software
development, or a little of both? I'm getting the feeling that the latter
might be the case.

     It's both.

>Secondly, what kind of operating system, applications, etc can one of the
MDS units run? I'm told that it is an ISIS based system, but I really don't
know much about ISIS. I assume it's a disk operating system, but beyond
that I'm clueless.

  See my webpage. This brings ups an interesting story, Gary Kidall was
hired by Intel to write PL/M as a compiler cpable of being used on the
MDS-800 to write microcomputer software. Apparently this was before the
MDS-800 was released and well before ISIS was released. Gary found that he
needed a file sytem to handle the files that he created so he wrote CPM. He
offered CPM to Intel but they didn't want it since they were already
developing ISIS in Israel. Big Mistake! If you look at the OLD CPM manuals
from Digital Research (Gary's company) you'll see a commented listing for
CPM in the back. It clearly states that it was written for the Intel
MDS-800! All other variants of CPM were modified from the MDS-800 version.

I'd like to think that there is some general-purpose OS I could run on it,
play some wumpus, trek or life, amortize my mortgage, or maybe fire up a
terminal emulator and get into the BBS scene.


>I'm clearly no expert in this old stuff, but I'm at least wise enough to
realize what I *don't* know. Can someone fill in a few of the gaps?
>My MDS has an 8080A CPU card in it, some kind of memory card, and a disk
controller. Also, a card that connects to a large ICE pod "Intel ICE-51",
if that helps.

  The last card is for the Intel 8051 CPU emulator. The rest of the cards
are standard (except the disk drive system and controller were optional).
See <> for pictures of one
of my MDS-800s and it's cards along with descriptions of a lot of the
various bits and pieces.


>TIA, Bill
Received on Thu Feb 03 2005 - 12:08:23 GMT

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