Weird Sys 6/7 MPU Board - Any info or schematics?

Working on a project Blackout, I went to take out the MPU to test it and noticed it wasn't a system 6 board; it had an unpopulated 12 pin connector on the top right edge. The two four pin connectors were moved to the left side. Examining it more I noted it has the system 7 style 7 segment display, and it has dual 2114 ram chips like a system 7. But it doesn't look like any system 7 board I've seen. Those have the roms sideways and the 12 pin connector is on the side. The 12 pin doesn't look to ever have been populated. The only marking I see is "5764-09465-01", but that doesn't return a single thing on google

I'm trying to diagnose why it won't boot, but since williams boards aren't screened, and the layout doesn't match any boards I know, I can't figure out which chip is which. Trying to cross reference just off part numbers to a system 7, it doesn't seem like all the connections are the same, though I could just be missing a trace somewhere.

Does anyone know what this is from or where I could find a schematic?

IMG_20181126_191421 (resized).jpg

#2 5 years ago

LOS

Theonlylilo

Pinside member

10y 46,900 466 12

Fantastic find!!! It seems the passage between sys6 to 7...
Follow!

#3 5 years ago

ZAC

zacaj

Some further looking seems to suggest that this is probably a full system 7 board, but jumpered for system 6? At least, the jumper below the middle rom is going to ground, not an address line, and is connected to pin 18, so I think that would swap from 2716 to 2732. I'll have to research if there are any other modifications necessary to use a system 7 board in a system 6. So maybe this is a board configured for backwards compatibility by williams sold as a replacement once they ran out of system 6 MPUs to use? I wasn't aware there were multiple generations of system 7 boards though...

#4 5 years ago

AMS

barakandl

nvram.weebly.com

12y 132K 10,414

That is neat. Does look like a sys 7 prototype.

I wonder if they spun this up after they ran out of ROM space on Firepower compared to the rest of the sys 6 games ROM setup.

#5 5 years ago

ZAC

zacaj

As another update, this isn't just a rearranged system 7. Some of the chip pinouts don't match up for the address decoders. Might be functionally the same, but at least using different logic gates within the 7400 chips

#6 5 years ago

HAN

HHaase

Siegecraft

14y 89,550 3,097 4 12

Definitely an interesting board to look at. Never seen one with a layout anything like that.

Sure looks like a prototype system 7 to me too, but makes sense they didn't populate the header for the speech PIA as you'd still be feeding from the driver board. Which means it was made before system 7 machines went into production.

Neat find, make sure to upload the photos to IPDB as well.

-Hans

#7 5 years ago

ZAC

zacaj

Quoted from HHaase:
Neat find, make sure to upload the photos to IPDB as well.

It would be nice to document this somewhere, but I don't know what game the board is necessarily from

#8 5 years ago

BOY

vid1900

Pinside member

Sana'a

12y 164K 40,201 18

Very cool.

What are the date codes on the unsocketed chips?

#9 5 years ago

ZAC

zacaj