View Full Version : Mystery boards found in an IBM AT 5170

July 16th, 2017, 10:34 AM
I recently rescued an IBM PC AT 5170 from recycling, and I'm glad I did! The machine boots up fine and seems to have several aftermarket upgrades. Even had the original case key!

In the system, I found two weird expansion boards that I haven't been able to find out anything about.

One is marked "BLUEBIRD SUPER SECURE" and has several slots for what looks like memory or cache? Only 4 of the slots are populated. The chips are labelled: "MMI PAL20X8CNS". I can't find any information on what these are.

The other is unmarked aside from a date of "1985". The board has what looks to be a big metal capacitor and a red LED that turns on when the computer is powered on.

Neither of these cards have any external connectors.

I haven't gotten a SETUP disk yet to check any additional configuration or software.


If anybody has a clue what these are, any insight would be greatly appreciated.

July 16th, 2017, 11:55 AM
For PAL chips, check out https://en.wikipedia.org/wiki/Programmable_Array_Logic

It's a complete guess (for amusement, hopefully someone actually knows what it does), but given the name of the board I figured a possible scenario might be that each PAL contains a cyrpto key, or logic to generate/validate keys for identification or secure transfers done via software.

July 16th, 2017, 12:01 PM
I doubt that it's anything that complicated. It looks like a big SRAM board--I don't find mention in my 1987 PC products catalog. 8 bit, so probably some mapping logic in there.

Other than providing a switch register, I haven't the faintest idea of what the small board does.

July 16th, 2017, 12:07 PM
Isnt' Bluebird a subsidiary of American Express ?
Could be a computer used for a payment system

July 16th, 2017, 12:10 PM
Or to read about the specific Monolithic Memories PAL designs https://archive.org/details/MonolithicMemories-MMI-PROMsPALsFIFOsAndMultipliersOCR

I think the smaller card is equivalent to a dongle. Bluebird Systems made a multi-user DOS aimed for security which in some versions included a parallel port dongle.

Larger card: I have no idea. Might be designed to be a multiplexer having multiple clients sharing a single serial port.

Is there anything special on the hard disk? Could be a great clue as to what the cards do.

Edit: Amex started Bluebird in 2012 so I doubt these cards relate to that.

July 16th, 2017, 12:28 PM
A preliminary keyword search brought me to Bluebird SuperDOS which appears to have possibly used hardware keys. You may have a set of them. I found reference to the late 90's version using a Parallel port key. Earlier systems may have used an ISA board. Can't find any specifics, but the name and date fits, as well as using keys later on.

Victory is mine, I found that there is a hardware KEY that plugs into the printer port that the customer was not aware of. This is what was keeping the system from booting. Once the Key was in place I adjusted the bios and got the system back on to working. it has been a while since I fiddled with a smoking fast PII MMX with 256MB of memory.

Bluebird Systems has introduced SuperDOS/286 and Business BASIC/286 for the IBM AT. Under SuperDOS/286, an AT can support up to 24 users sharing up to 82 megabytes of disk storage. As Business BASIC/286 is a superset of Data General’s Business BASIC, AT users can take advantage of the decade-old library of Data General BASIC programs...

July 16th, 2017, 12:37 PM
I think the smaller card is equivalent to a dongle. Bluebird Systems made a multi-user DOS aimed for security which in some versions included a parallel port dongle.

You beat me to it.