[rescue] Sun-3 memory board troubleshooting

[John Hudak]

Well, a technique based on some assumptions:
Assume MMU is disabled (Don't know if this machine has one)
Assume the diagnostics start a absolute mem location 00
Assume you have a schematic with enough detail to determine memory decoding

Determine on the board where the lowest address segment is located on the
memory board
HW designers usually followed a order in memory chip layout, startng with
the 'top' row as the first segment..
Based on the memory chips used, determine the address range of each
segment.  e.g. sketch a memory map.
Map the memory location of the failure to the memory segment (this gets you
into the correct set (row) of chips. )

Determining the exact chip requires finer granularity of troubleshooting
gear..e.g. logic analyzer, possibly a scope and possibly a more detailed
schematic.  Things get very tough at this point.

Without having seen the board, I can't give much more help...12MB?  ouch!
good luck
J



On Wed, Aug 2, 2017 at 4:07 PM, Peter Stokes <peter at ashlyn.co.uk> wrote:

> Hi Scott
>
> If all else fails, try a methodical swapping round of chips and watch the
> error move?
>
> Sounds a tedious process I guess, but better than random changes?
>
> Peter
>
> Sent from my iPad
>
> > On 2 Aug 2017, at 21:23, Scott Quinn <saquinn624 at aol.com> wrote:
> >
> > I pulled out my 3/110 for verification of my spare 3/110 CPU, but now
> under
> heavy diagnostics the 3/110 shows a parity error on the 12MB+SCSI expansion
> board.
> >
> >
> > I tried re-seating all the chips, no change.
> > The error on the console is "Parity error at address 0x00D3F428 EXP
> 0x2C5A5A97, Obs 0x2DA5A97" (and the expected parity calc.)
> > Anyone have tips for how to map from the address to the board-level ICs
> on
> the Sun-3 memory expansion/SCSI card? I have some spare memory chips out
> from
> fixing a parity issue on the spare CPU board.
> > _______________________________________________
> > rescue list - http://www.sunhelp.org/mailman/listinfo/rescue
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