Sizing Up Servers: Intel's Skylake-SP Xeon versus AMD's EPYC 7000

All in all, whhen you have a server that seems so close in performance to Intel for less money and consuming less power, I can't imagine that EPYC won't see broad adoption and Intel won't be squeezed.

I'm glad AMD is back and there is renewed competition in the server market!

1. The mesh interconnect looks like a big loser for the smaller parts. It's a big jump up in complexity (there's an academic paper floating around which describes the guts of an early-stage version) and seems to be a power and performance drain. I can't imagine they got the clock speeds they wanted out of it. Sure, it's probably necessary for the high-core-count SKUs, but the ring bus probably would have done a lot better for the smaller ones.

2. There's almost nothing in here for high-end workstations (which typically have launched with the server parts). Sure, AMD has Threadripper coming soon, but this looks like Intel's full lineup... so where are the parts? We've bought plenty of Xeon E5-1650s and 1660s around here, and it doesn't look like there's anything here to replace them. That's unexpected. The "Gold 5122" (ugh what a silly name) is comparable, but at $1221 is priced just about double what an E5-1650v4 runs.

Workstations are a bit of an interesting case because their loads look a lot more like a "gaming desktop" than a server: a few cores loaded most of the time with occasional bursts of high-thread-count loads. That typically favors big caches, fewer cores, and aggressive clock boosting. If you're only running max thread count every now and then, you can afford a huge frequency hit when you do. But since these are business systems we try to avoid anything that doesn't say "Xeon" on it (or "Opteron", in years past) as reliability is paramount. To see nothing here from Intel in this launch is discouraging, to say the least. I have an upgrade budget and it looks like it'll be heading nVidia's way at this point.

> This pricing seems crazy, but it is worth pointing out a couple of things. The companies that buy these parts, namely the big HPC clients, do not pay these prices.

We in HPC would not touch these outside big memory systems which is even niche for us. The consumers of these are far more likely to be those with data warehouse style needs (a.k.a Oracle customers).

Much like the rest of the world 2 socket systems in HPC are by far the most common.

<disclaimer, I work for DO>

Looks pretty solid. Sure not everything scales linearly with corecount but if your task does, it looks like AMD might be worth considering.

"What does this mean to the end user? The 64 MB L3 on the spec sheet does not really exist. In fact even the 16 MB L3 on a single Zeppelin die consists of two 8 MB L3-caches. There is no cache that truly functions as single, unified L3-cache on the MCM; instead there are eight separate 8 MB L3-caches."

Also:

"AMD's unloaded latency is very competitive under 8 MB, and is a vast improvement over previous AMD server CPUs. Unfortunately, accessing more 8 MB incurs worse latency than a Broadwell core accessing DRAM. Due to the slow L3-cache access, AMD's DRAM access is also the slowest. The importance of unloaded DRAM latency should of course not be exaggerated: in most applications most of the loads are done in the caches. Still, it is bad news for applications with pointer chasing or other latency-sensitive operations."

I was kind of expecting this, but it's still disappointing to see. Looks like if you need a lot of L3, Intel is still the best/only option. Not to say that AMD hasn't made massive improvements though - and it's also worth noting that while AMD's memory latency is generally worse, throughput is also typically better than Intel.

Wondering other than some sparse matrix applications known to be memory bandwidth bound, what kind of performance impact this is going to cause. Is there any real memory bandwidth bound applications other than ML/AI stuff used by those Internet big names?

AFAIK, GitLab's server proposal included them. They will probably not use 128GB TSV LR-DIMMs immediately though. I think the price gap between 32GB RDIMMs and 64GB LR-DIMMs are falling right now right?