23 Apr
2016
23 Apr
'16
8:34 a.m.
On Sat, 23 Apr 2016, Robert Jarratt wrote:
I don't think the SROM diagnostics are going to help much because the
failure is in the DROM sequence, which comes after the SROM.
But from the discussion referred I gather DROM outputs its diagnostics to
this port too and you might be able to learn what exactly about NVRAM it
complains. Also you might be able to correct configuration, e.g. by
poking at NVRAM or elsewhere appropriately; notice that the manual also
suggests you might be able to bypass the DROM sequence and go to SRM/ARC
directly, which might help recovery too.
It's up to you if you want to try this of course, I just thought it might
help as the existence of this SROM console might not be universally known.
It is separately decoded on the flashbus (among flashROM, DROM,
diagnostic LEDs and jumpers), so I doubt it's in an ASIC, that would be
too arcane. I suspect they wanted to keep it separate from flashROM for
safety.
That's a
bit cryptic, but knowing that this is a low-level CPU interface
you can
gather the wiring from this document:
<http://h18000.www1.hp.com/cpq-
alphaserver/technology/literature/164lxtrm.pdf>.
So BSROMCLK is Tx and SROMCDAT is Rx, but as noted here and in the
discussion in the first reference you need an EIA/TIA 232 driver and
receiver
(there is power available on the diagnostic port,
so you can use it for
the
circuit), and of course you need to cross the
lines wiring them to your
host.
Finally the
SROM console command reference is here:
<http://h18000.www1.hp.com/cpq-
alphaserver/technology/literature/srommini.pdf>.
This manual doesn't specifically cover the Avanti, but I'd expect the user
interface to be similar -- it's a low-level tool close to the CPU after
all.
NB on Avanti the 8kB NVRAM is separate from the TOY/NVR chip (which is a
Benchmarq BQ4285, providing 114B of general storage only).
I had already located the Benchmarq chip and found the spec to be
insufficient for the 8K NVRAM. The problem is, I don't know which chip has
the NVRAM, I have not been able to locate it and the manuals don't tell me.
I hope it isn't one of the ASICs. I have posted a photo of the board here:
http://bit.ly/1qHQnaB in case anyone can id the NVRAM. If the NVRAM contents are maintained by the battery
then there should be a
way to reset the NVRAM contents, but there does not seem to be a way. I
wonder if the NVRAM persists without power? The manual seems to say that the
TOY is battery backed, but makes no mention of the NVRAM needing the
battery.
It is battery backed indeed and it sits right in the upper right hand
corner: <http://web.mit.edu/6.111/www/s2007/datasheets/KM6264B.pdf>, next
to the other flashbus devices, as expected -- next to the left there is a
pair of flashROMs (and a pair of sockets for another two of the four
supported total), and a socketed DROM chip. Being decoded as a DRAM bank
they are also close to DRAM sockets. Jumpers and LEDs are elsewhere, but
obviously they have less strict PCB routing requirements.
HTH,
Maciej