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Small nitpick, but if I'm reading this correctly, the EPYC 7371 is a 16-core part. The Threadripper 2950x with 16 cores and the 2970wx with 24 cores both have f
by llampx 8y ago
Small nitpick, but if I'm reading this correctly, the EPYC 7371 is a 16-core part. The Threadripper 2950x with 16 cores and the 2970wx with 24 cores both have full speed memory access for all cores. It is only the 32 core 2990wx that has half the cores running without direct access to memory. Do correct me if I'm wrong.
- gigatexal 8y agoYou could be right. I was under the impression that all mainstream parts even the threadripper ones were artificially handicapped.
- duhast 8y agoEPYC supports up to 8 memory channels where as Threadripper only 4.
- loeg 8y agoSure, but that's 32-core EPYC (4 dies, each die has 2 channels). Does this 16-core part use 2 dies or 4 dies (with half of each die's cores crippled)?
- Tuna-Fish 8y agoAll EPYC cpus support 8 memory channels, and the full set of PCI-E lanes. AMD has chosen to segment the market so that every CPU plugged into every existing SP3 MB can make full use of all it's features. This CPU has 4 dies, each of which have 2 CCX, each of which have 2 cores and 8MB of cache.
- deleted 8y ago[deleted]
- atq2119 8y agoThe 24-core Threadripper doesn't have full memory bandwidth from all dies. It's build from 4 dies with 6 enabled cores each, and like for the 32-core Threadripper, only 2 of those dies have memory channels enabled. You're right about the 16-core Threadripper being built from 2 dies, though the EPYC should still be able to do better at I/O, since I believe it's built from 4 dies, all of which have active memory controllers. So you basically get 2x the memory bandwidth.
- zamadatix 8y agoDirect access is half the equation, 8 vs 4 memory controllers means half the memory bandwidth.
- dragontamer 8y agoYou are missing important details. The fundamental building block of AMD is the CCX: CPU Complex. AMD's design has 2-CCX per manufactured die, and then they glue dies together. Each CCX is manufactured with 8MB L3 cache + 4-cores. All of AMD's chips are combinations of this "Zeppelin" die. AMD Ryzen is 1xdie, Threadripper is 2x or 4x dies, while EPYC is always 4x dies per chip. Threadripper is 2-dies of (4+4)x2 == 16 total cores. The 2970wx is 4-dies of (3+3)x4 == 24 total cores (1-core broken in each CCX). Ryzen 2600X is a single die of (3+3) == 6 core. The EPYC 7371 is the "most broken" of them all, (2+2)x4 == 16 total cores. But each 2-core CCX has the full 8MB of L3 cache to work with still, so it ends up being a good performer anyway. And I guess with so many cores broken, they can send a lot of power into the part and ramp up the GHz. In short: the 7371 can command a low price because its technically an incredibly defective design. Of the 32-cores which were attempted to be manufactured, only 16 of them passes quality control. AMD then configures them to have a high GHz and... what do you know? It performs pretty well.
- llampx 8y agoThanks for the detailed breakdown, it makes a lot more sense now.