FPGA VAX update, now DIY TTL computers
ard at p850ug1.demon.co.uk
Thu Nov 3 13:53:29 CST 2005
> 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
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.
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