> > >> No, it uses the parity bits. Only 8 syndrome bits are needed
> > >> for 64bit words.
> > >
> > > Hmm. So does that mean the ECC is limited to single (odd
> > >number of) bit errors?
> > ECC has single bit error correction and 2 bit error detection. Better than
> > parity no matter how you slice it.
Only if you have memory that is failing or you need extreamly reliable
operation (good memory should have a single bit error rate of something
like 1 in 10 years).
> I have not tried it on D-P, but Rod says that the Triton-II ECC imposes an
> extra delay in memory accesses, i.e. "don't use it".
The cost is about 10 to 15% in memory bandwidth.
> That should be really easy to see if you go looking for it.
Yep... easy to spot in any bcopy benchmark larger than the cache.
Rod Grimes firstname.lastname@example.org
Accurate Automation Company Reliable computers for FreeBSD