From: Tony Duell <ard_at_p850ug1.demon.co.uk>
>> Is it? Someone also told me that parity was usually faster, though.
True?
>
>There's no reason at all why parity memory should be faster than
>non-parity memory. Parity memory just stores a parity bit for each byte
The assumption is that parity is available at the ram at the time of
write
and while true it was calculated some where.
Parity can only be calculated (simple combinational logic with attendant
delays) at the time of a wirte so the write must for a given ram speed
take longer. So if you want the parity to fit in a given memory write
cycle time you must use faster ram.
>of normal data, so you can detect (but not recover from) some memory
errors.
There is also ECC ram, those are slower (over all) as the ECC bits have
to be
calculated. Expensive, errors are caught and recovery is possible.
Allison
Received on Sat Jan 27 2001 - 13:48:06 GMT