Peter
I indeed have a bit of practical experience to share on O2s and RAM.
We have Bruker spectrometers with O2's and when we received them, I rapidly
planned a memory upgrade in order to speed work on these boxes. Considering
the O2's peculiar internal architecture, it seemed - and it still does seems
so today - that 64Mb is rather unefficient. So I upgraded my O2s to more
than 256Mb. Then problems started, the spectrometers kept crashing for no
apparent reasons and not totally reproducibly.
Finally, it turned out that there is a *bug* in Irix 6.3 that makes the O2
crash in the situation where the following three conditions are
simultaneously fulfilled:
(1) there are two Ethernet cards active
(2) there are more than 256Mb of RAM
(3) the RAMs are from different origins (vendor)
The patches installed for allowing Irix 6.3 to handle more than 256Mb do not
seem to matter, read they all fail. SGI does not seem to care either. Their
first reaction was: this extra RAM is not SGIs', so none of our business.
Further on, I basically got the you-just-have-to-upgrade-to-6.5 talk. How
did I solve the problem in practice ? It turns out that the bug is only
active when the RAMs are from different hardware sources, so I concentrated
all SGI's RAMs into some of the boxes and the other vendor's RAM in the
other boxes and the problem **disappeared**. Gone ! All my O2 run as
perfectly as an O2 can run on more than 256Mb.
In your case, if you get your O2 to work with 160Mb, you are probably well
off. If your available RAMs allows you, you can go up to 256Mb and it should
work as well as with 160Mb, no matter what patches you have (they are
actually not used up to 256Mb). Below 256Mb, it worked in my experience with
whatever mixture of RAM sources (I had three to mix and match...).
A small point to note that the sensitivity to different RAMs is a known
weakness from some UNIX boxes, but I found it pretty ironic that SGI is
buying its RAMs from the same vendor I got my extra ones, tests them
somewhat, throws away a few (many ?) and sells the resulting ones for ~5
times the original price. And does not even support their (co)existence
properly.
> I hesitate to go from 6.3 to 6.5 as my programs runs
> ok presently, at least with 160 Mbyte memory.
It is possible that this is not a problem anymore under Irix 6.5, but I have
no experience since I did not migrate, yet. But I will soon for Y2K reasons
(Irix 6.3 is not guaranteed by SGI, even with all the Y2K patches). A reason
to move anyway ?
Good luck
Sebastien
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Dr. Sebastien Vincent sebastien.vincent@rdls.nestle.com
Nestle Research Center Tel.: ++ 41 21 785 9165
Vers-chez-les-Blanc Fax: ++ 41 21 785 8925
CH - 1000 Lausanne 26, Switzerland
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