27 Sep
2023
27 Sep
'23
12:14 p.m.
/me hears mention of dead NVRAMs and materializes
Pulled out my UltraBook IIe today, it's fine with a dead NVRAM, just gives you the
usual "IDPROM contents are invalid" message you see on Suns.
If I'd have to guess, based on past experience, you likely have a counterfeit DS1553W
or you ordered the DS1553 without the W suffix. The W means 3.3V part. On a 3.3V system,
the DS1553 5V part will never release write lock-out; furthermore, the DS1553 has a
power-on reset comparator and will never de-assert reset either! I don't know if the
UltraBooks use this reset output, but if I were designing a system and using the DS1553/W,
I certainly would.
A missing DS1742W in a SGI Tezro stops it dead, as does a DS1742 5V part (W suffix is,
again, 3.3V). Part of what took so long on my designing a replacement for the DS1742W was
the sacrificial modules that were sent to me were...wait for it...Chinese counterfeits!
The part numbers from the dissected modules were all 5V parts!
Now the good news is, I can probably make replacements for the DS1553W. I already have a
prototype replacement for the DS1643, some customer must've needed it for a one-off as
I've never run more, but that should already be a solved problem. I have one or two
GW-1643-1 prototypes on hand for testing.
Thanks,
Jonathan