Memory Voltage on MicroVAX II

Jon Elson elson at
Sat Dec 5 17:40:04 CST 2015

On 12/05/2015 01:49 PM, Robert Jarratt wrote:
> As the 5V seems fine, the ripple seemed to be about 20mV 
> (although I am going to check again), I do wonder what 
> could be causing the memory modules to appear to be 
> failing. I am hoping that re-seating will cure it. Regards 
> Rob 
I ran a uVAX-II for 21 years here in my house.  It was HOT 
STUFF when I first got it in 1986!  By 2007, it was the 
slowest computer in the house.  It ran continuously during 
that period (at the end, it was only running a home 
environmental monitoring program, or I would have shut it 
down earlier.)

Anyway, after some years of flawless operation, I started 
getting crashes every couple months.  When it would hang, I 
would power down and re-seat all the boards.  It seems like 
it was usually a failure of one of the grant chains (either 
interrupt or DMA) and the disk controller would not be able 
to transfer.  Every once in a while I'd pull all the boards 
and vacuum out the backplane and gently vacuum off the 
boards.  That sort of helped, maybe.

The external UVII memory also had ribbon cables across the 
boards. Rough handling of these cables can cause intermittents.


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