Mystery RAM board?

[bluejazzer]

I recently acquired a 520ST, and decided to give it a look internally because I may end up routing power to an Ultrasatan through the hole left by a removed standoff on the HDD connector, and when I got it open, I discovered that there was clearly an expansion board of some kind fitted to it.

 

It's definitely a RAM board because it's populated with 41256s -- 16 of them, to be specific, so I'm guessing this is a 512K expansion board. It has 16 empty and 16 populated chip sockets. The empty ones are marked "bank 0 low" and "bank 0 hi" (8 each), and the populated ones are marked "bank 1 low" and "bank 1 hi" (again, 8 each). However, what's strange is how the board mounts. It has two spade connectors that are screwed down to the motherboard -- one along the ground plane (the center motherboard screw), the other slipped in between a standoff on the printer port. There are a set of pins at what looks like 1mm spacing pointing down that look like they press into the PLCC socket at U15, and sure enough, if I look at the socket, the contacts are pushed in on both sides at the points where the pins look like they insert. 

 

The only indication on the silkscreen are the words:

 

tech-specialities Co.

Houston, TX

520A r2.11

 

The motherboard is a Rev E, and I've attached pictures.

 

I've heard that the 520ST is basically heavily crippled by the miniscule amount of RAM it leaves available and that boards to expand it to 1MB were very common, but are a major task to fit because the footprint of the motherboard and case simply doesn't really allow for expansion. Is this board even safe to use?

 

Pictures are: Full motherboard with RAM expansion in place; RAM expansion flipped over (it's still attached via the ribbon cables underneath the can); bent pins on PLCC socket (U15) where RAM expansion appears to push in.

[LouisB]

Did you find out anything else about this board?  I just opened up an Atari 520ST and it has the same exact board in there! 😮  Seems this board needs to be re-seated often 🤔 

 

Mine has the battery & dallas clock chip on there.  I wonder if I can unearth the software, or does the clock work with the OS native?  Guess I'll find out.

Atari st tech-specialities Co houston, tx 520A r2.11

 

Edited September 3, 2023 by LouisB