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A comment on AMD's EPYC 9355P: Inside a 32 Core Zen 5 Server Chip. Parent comment

Re:AMD's EPYC 9355P: Inside a 32 Core Zen 5 Server Chip by jauntywundrkind on Monday October 06, 2025 @12:45AM (#45487703)
> Existing servers typically have 12 channels per socket, but they also have two DIMMs per channel, so you could double the number of channels per socket without taking up any more space for slots. You could also use CAMM which takes up less space.

Usually this comes at a pretty sizable hit to MHz available. For example STH notes that their Zen5 ASRock Rack EPYC4000D4U goes from DDR5-5600 down to DDR5-3600 with the second slot populated, a 35% drop in throughput. https://www.servethehome.com/amd-epyc-4005-grado-is-great-an...

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Re:AMD's EPYC 9355P: Inside a 32 Core Zen 5 Server Chip by AnthonyMouse on Monday October 06, 2025 @01:10AM (#45487815)
It comes with a drop in performance because there are then two sticks on the same channel. Having the same number of slots and twice as many channels would be a way around that.

(It's also because of servers being ultra-cautious again. The desktops say the same thing in the manual but then don't enforce it in the BIOS and people run two sticks per channel at the full speed all over the place.)

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