By: David Kanter (dkanter.delete@this.realworldtech.com), September 16, 2022 9:44 pm
Room: Moderated Discussions
anon2 (anon.delete@this.anon.com) on September 15, 2022 7:04 pm wrote:
> What is expensive about L1 ECC which is less costly in L2?
Most L1Ds are writeback. They also receive many partial writes (e.g., byte writes, 2B, 4B, etc.). ECC forces every write to trigger a full cache line read and write. In the L2, most writes are at full line granularity. In the L1, most writes are less than a full line.
Also, ECC read+calc+write adds latency (as others noted above).
David
> What is expensive about L1 ECC which is less costly in L2?
Most L1Ds are writeback. They also receive many partial writes (e.g., byte writes, 2B, 4B, etc.). ECC forces every write to trigger a full cache line read and write. In the L2, most writes are at full line granularity. In the L1, most writes are less than a full line.
Also, ECC read+calc+write adds latency (as others noted above).
David
