13 May
2006
13 May
'06
3:14 a.m.
On May 13 2006, 9:32, Jochen Kunz wrote:
On Fri, 12 May 2006 23:21:10 +0200
Gerhard Lenerz <mail at g-lenerz.de> wrote:
RAM.
No need for ECC RAM
ECC == parity? I
always thought the SGI machines need ECC / parity (I.e. SIMMS with 36 data bits.)
ECC != parity.
Parity uses a single bit (in the case of 36-bit SIMMs, one bit per
byte) to detect single-bit errors. It will tell you a byte is wrong,
but won't tell you which bit, so it provides no correction capability.
It will not detect two-bit errors.
ECC stands for error correction code, and is a multi-bit arrangement
capable of not only detecting errors but providing enough information
to correct some of them. How much it detects and provides correction
for, depends on how many bits and how they're organised.
--
Pete Peter Turnbull
Network Manager
University of York