[rescue] Sun 3U Expansion Memory Questions

Patrick Finnegan pat at vax11.net
Thu Jul 18 16:49:09 CDT 2019

On Thu, Jul 18, 2019 at 3:57 PM systems_glitch <systems.glitch at gmail.com>

> Yep, you called it, it's the old Clearpoint logo. Anyone have information
> on this board? Joe Zatarski suggested I map it out with the logic analyzer
> as he did for his VAX RAM board, but I'd rather not :P
I'd hook a scope up to the chips, and see if you can find any ones that
have the output "stuck" on or off.

My usual method works better with socketed chips - start pulling some and
see how they map out based on the new parity errors you get.  You could
probaly do this -- cut the DO pin from the chip, see how it maps, and then
solder it back together -- unless you have good tools, I wouldn't try
unsoldering the chip intact.

Assuming you can get to an Open Boot prompt, I'd make some Forth code
read/write patters to the ram, and try to find the error.

Anything you do is probably going to be time consuming, unless you can find
better documentation on the board.


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