AlphaStation 200 NVRAM Problem

[Maciej W. Rozycki]

On Sat, 23 Apr 2016, Robert Jarratt wrote:

> >  Second: it may also be that DROM itself is faulty, a bit may have flipped
> for
> > example; NB this is UV EPROM, so things happen.  Maybe someone can
> > share a known-good image.
> > 
> 
> When I put the DROM back the failure returned. So it is either a bad SRAM, a
> short/open somewhere, or the DROM code itself. I have a PROM programmer, but
> it is only for DIP packages, I don't have the facilities to read a PROM in
> this type of package. I will have another look round for any obvious
> problems on the board, but it looked OK to me when I checked. Getting the
> SROM diags out might help too, I will have a look at that.

 First of all you might be able to run some SRAM diagnostics yourself, 
either from the console (if it has a tool for this; at worst you could 
poke at it manually with deposit/examine commands, but the complicated 
flashbus access protocol will make it a tedious task unless there is a way 
to script it) or from the OS (can't help how to do this from VMS; under 
Linux you could mmap(2) /dev/mem at the right address and then poke at it 
with a little program doing the right dance to get the flashbus access 
protocol right), to see if it shows any symptoms of misbehaviour.

 To experiment with DROM you might be able to find a DIP-to-PLCC socket 
adapter, pinouts for ROMs are pretty standard I believe.  A ROM emulator 
might help too if you can get your hands on one, second-hand units are not 
exactly expensive nowadays as they went out of favour it would seem.

 Overall, hard to say which failure case would be better (or worse).  It 
looks to me like at this point you have several options to proceed with.  

 Good luck with your investigation and recovery!  I wish I had one of 
these machines, they are sweet and they run Linux out of the box. ;)

  Maciej