new find: an Intel MDS 800

From: Dave Mabry <>
Date: Sat Oct 30 10:07:08 2004

Yeah, that white MDS-800 is the first I've seen as well. Very cool, I

As for the BIOS in CP/M, it is actually not much different between the
SD and the DD controller boardset. They take the exact same command
set, as I remember. The only real difference is the range of sector
numbers, as there are merely more sectors on the DD diskettes. The
sectors themselves are the same size. They used different I/O ranges
for the control ports, but that was about it.

The original DRI CP/M-80, right out of the box from Digital Research,
would boot on an MDS-800 with the SD controller boards. That is the way
an OEM would get it and they would rewrite the BIOS for their hardware.
   Kildall wrote the original CP/M for that exact system, the MDS-800
with Single Density controllers (the SBC-201).

I did a lot of rewriting on my version of the BIOS in order to handle
the internal SD drive on a Series II as a fifth drive (the first four
were the ones that the SBC-202 DD controller could handle). The CP/M
that I bought from Intel supported having BOTH the SD and the DD
controllers in the system at the same time, but Intel never supported
CP/M and the internal drive on the Series II.


Joe R. wrote:
> That's interesting. I've never even heard of a white MDS-800 before. Was
> it painted white originally or was it painted over an orginal blue one?
> I think you need a lot more than rewriting the BIOS to handle DD disks.
> Intels DD controller has a 3000 series bit-slice CPU and some other odd
> circuitry to handle DD.
> Joe
> At 11:39 AM 10/29/04 +0200, you wrote:
>>I have a white MDS 800 System. It was sold in Germany by Siemens and they
>>relabelled it to SME 800 ("Siemens Microcomputer Entwicklungssystem").
>>It has an external 8"-double drive and a dumb terminal. Inside it is all
>>Intel. The only thing they changed internal: The glued "Siemens"-labels
>>over the original Intel-logos on the PCBs.
>>You can see it:
>>We are running ISIS-II inclusive KERMIT on it. One time Christian Corti
>>succeeded to boot a CP/M 2.?. But in the meantime this disk was damaged.
>>I found a very old CP/M source, dated "11/21/75" in the net, written in
>>PL/M and was able to translate it with the original PL/M-compiler
>>written in FORTRAN (dated: JAN 1975) on our SUN 4/260.
>>What is needed: To adapt the original BIOS for single density disks to
>>the double density drives on our system and to make bootable floppies.
>> Klemens
>>On Wed, 27 Oct 2004, Steve Thatcher wrote:
>>>I lived in Munich, Germany for a year and a half back in 1983 while I was
>>>working for Applied Microsystems. I developed a couple of the EM series
>>>emulators and ran into a number of remarked Intel systems that said
> Siemens
>>>on the outside.
>>>> I've never heard of a Siemans system. The white MDSs that I've seen all
>>>>have the standard Intel markings and labels. (I've got one sitting about 3
>>>>feet from me as I type.)
>>>> Joe
>>klemens krause
>>Stuttgarter KompetenzZentrum fyr Minimal- & Retrocomputing.
Received on Sat Oct 30 2004 - 10:07:08 BST

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