5 ms·
Commodity PCs back in the 80s and 90s didn't have error correction but they did have parity (iirc). Correction requires three extra bits per byte compared to pa
by greenbit 4y ago
Commodity PCs back in the 80s and 90s didn't have error correction but they did have parity (iirc). Correction requires three extra bits per byte compared to parity only carrying one extra bit per byte. I recall around 1990 you could get your 30pin SIMs as 9-bit (parity) or 8-bit (no-parity), and virtually all of the PCs at the time wanted the 9 bit modules. Parity can't correct errors, but at least it can cause an exception when you read something that's had a bit flip.
- Felger 4y agoYes I can indeed recall systems being shipped with 4x 9-bits sticks. And god the horrific price of thoses sticks...
- Dylan16807 4y agoOn current memory, parity and correction get applied to the entire bus width. So with parity taking one bit, and correction taking log2(width) bits, it only requires 7-8 bits to apply both of them to an entire memory channel. (DDR4 has 64/72 bit channels, and DDR5 has 32/40 bit channels)