Re:Apple Preps Next Mac Chips with Aim to Outclass Highest-E...
by dragontamer on Monday December 07, 2020 @03:44PM
(#25337238)
HBM's latency characteristics are about the same as any other DRAM however (including DDR4 or LPDDR4x).
So you have a high-bandwidth, but no better latency, L4 chip. And that's kind of hard to deal with and optimized against.
Xeon Phi had a DDR4 + HMC (where HMC was a early competitor to HBM), and getting good performance out of that was unusual. DDR4 ended up having slightly better latency, so the HMC cache would hurt some workloads.
So you have a high-bandwidth, but no better latency, L4 chip. And that's kind of hard to deal with and optimized against.
Xeon Phi had a DDR4 + HMC (where HMC was a early competitor to HBM), and getting good performance out of that was unusual. DDR4 ended up having slightly better latency, so the HMC cache would hurt some workloads.