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Sun 3/50 with Parity Systems RAM Upgrade


Veteran Member
Feb 1, 2010
Central VA
Finally did a writeup on my Sun 3/50:

Here's the machine set up and running:

Before powering it up, I opened the machine and cleaned it. I was surprised to find this:

It's a Parity Systems RAM upgrade! It's actually two boards with a jumper ribbon:

This board adds 4 MB of RAM, for a total of 8 MB. It's got empty SIMM sockets, but I can't find documentation on it, and just adding more RAM doesn't cause it to show up. Anyone have documentation on this one?


Experienced Member
Jul 25, 2022
You are missing the very best part of the 3/50 there, the giant monitor! The serial ports were kinda slow and kludgy.
I had a similar memory boards BITD, but I got it fully populated so had no experience with configuration.


Experienced Member
Aug 17, 2015
Kansas City area, US
From http://www.verycomputer.com/39_a348c9fca4233740_1.htm
>I've got a 3/50 at home with one of these cards that has been running
>with 4Mb installed on the card for a total of 8Mb system memory.
>I installed another 4Mb, but the system still reports 8Mb when it
>comes up. Tried the same thing on another motherboard with the
>same result.
>There don't seem to be any jumpers to set on the daughter board.
>eeprom reports
> memsize=4
> memtest=4
>which doesn't seem to match what is installed.
The EEPROM parameters for the ammount of memory fitted and the ammount
tested can be easily altered. Just type 'eeprom memsize=x memtest=x',
where 'x' is the number of megabytes that is installed (in your case, this
would be 12), shutdown the machine (using 'halt'), then type 'k 2' at the
PROM monitor prompt.

This will warm-boot the machine as though it's just been turned on, and it
should report the correct RAM size and test the relevant ammount during
the power-on self-test.