[Beowulf] cheap PCs this christmas

[Mark Hahn]

> > more to the point, if you're going to network $300 PCs, ECC should almost
> > certainly not be on your xmas list...
> 
> I'm not sure why. The Sun Fire X2100 (double the price of $300 PCs, 
> admittedly) take DDR 400 (PC3200) unbuffered ECC memory, which is 

I had the impression that the $745 list for that computer was pretty
much a barebones price.  does it even include a CPU?  (CPUs are opteron
1xx's, which start at $200 just by themselves.)  but any s939 should 
support ECC, I believe.

well, I just looked at pricewatch dimms, and for 1G, the difference
is 105 vs 59 (recognizable brand).  I have lost touch with how damn cheap
this stuff is!  so, omitting ECC from a $300 PC only saves $45, which is 
still enough to think about.  obviously, desktops use less ram, therefore 
have fewer failures to detect, making ECC less valuable.  desktops also
usually do not run 24x7, again reducing the value of ECC.  I seem to 
recall that there is a term of memory corruptions that depends on how 
"hard" you use it, as well.  and as others pointed out, altitude,
temperature, etc.

error rates (at my altitude) seem low enough that I see ECC's main value
in burnin and health-monitoring.  I suspect that if a dimm's bad, you'll
notice it through other means, but an increasing trend of ECC events can 
tip you off earlier (and more specifically).

regards, mark hahn.