> > ECC is just parity RAM, the memory controller in the chipset detects
> > single bit errors and recalculates the correct bit.
>
> That would be a good trick. A parity bit will let you find out about a
> single-bit error, but you need more redundant bits to tell you which bit
> to invert. If your memory is organized as 32-bit words, for example,
> the controller needs to come up with a number between 0 and 31 to
> identify the bad bit. That takes another five bits.
`Parity' SIMMs for PCs have four parity bits for every 32-bit word.
Some chipsets will use all four to calculate ECC on a 32-bit word,
rather than one each of the four to calculate parity for each octet
within the word.
cjs
Curt Sampson cjs@portal.ca Info at http://www.portal.ca/
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