new find: an Intel MDS 800

From: Steve Thatcher <>
Date: Wed Oct 27 05:43:21 2004

as for the DC37 on the back (yes, they do consider it a d-sub style connector). The more important question is what the two bottom cards are in the card cage. They are normally a two board disk controller from Intel (bit slice processor). As long as the controller was made by Intel, then the DC37 pinout should be compatible with this hardware or Intel's. I seem to recall a company called Zendex that made compatible items for the MDS series.

Intel made a MDS220 and a MDS230. In either one, you could make a choice as to the density of the internal drive. As I said before, if there is a 50 pin ribbon cable between the back board (IOC) and the drive, then it is wired for SD. If an internal cable comes from the front to the disk drive, then it is wired as DD. I have both types of cables at home...

About your comment on monitor troubleshooting. I have the schematic set for the Ball Brothers monitor that was usually used in the MDS2XX series. The nice thing about the monitor is that it is very simple. There is no fancy monitor control chip in it, in fact it doesn't even have any chips on it if I recall correctly. The monitor was usually supplied by Ball Brothers or Zenith. The back IOC supplies +12V poower, vertical, horizontal, and video intensity signals for display.

By the way, the top card with all the switches on it is the CPU card. There were three versions of it that I know of. The first was 8080 based and only had 32K on it. I believe the remaining two versions were 8085 based with the first having 32K and the final one having 64K. If you only have 16 ram chips on your cpu board, then the next card down would or should be a 32K ram card.

best regards, Steve Thatcher (one of the other MDS guys)

-----Original Message-----
From: Scott Stevens <>
>The internal drive could be either SD or DD. If there is a 50 pin ribbon
>connecting the drive to the back board in the system, then you have an
>internal single density drive. If there is a cable running from one of the
>front cards to the drive, then it has been hooked up as double density.

Actually, there's an added-in non-Intel jack on the back (I think 37
pin 'D' shaped but as everybody knows, probably not a 'Dsub' due to
size) that the external dual-8" floppy enclosure plugs into. I
suspect the system may have had something third-party added to support
the two external drives, and some of the disks are labeled to indicate
they are 'higher' density than the internal drive will support.
Received on Wed Oct 27 2004 - 05:43:21 BST

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