3 Nov
2005
3 Nov
'05
7:53 p.m.
How does parity memory work? Must one use the extra bit for parity or
could one use it as a ninth data bit?
Genuine parity memory does, indeed, store 9 bits, and you can use it as 9
bit wide RAM. Certainly some of the old 30 pin SIMMs were genuinely 9
bits wide.
There was a hrrible thing called fake parity memory. It stored 8 bits and
calaculted the parity bit on a read (ignored the incoming parity bit on a
write) to keep the memory controller happy. Of course you can't store 9
bits in that type of device.
-tony