[lstamour]

I was curious as to what Intel’s number’s look like. Found the 2nd gen Ryzen matched the random latency for the 7th gen i7, but while the 3rd gen at 3733CL17 gets 67ns, it’s 53-54 ns for the 8th and 9th gen i7/i9. So that’s narrowed to 13 ns slower, a 24% drop in performance (or a 20% improvement, depending on how you look at it...) While it does matter, we’re comparing 8 core parts to 12 core parts, so it’s possible that 50% more cores outweighs a 24% increase in memory latency, or alternatively that 33% fewer cores could hurt performance more than 20% faster memory latency. Ehh... it’s a mixed bag for me. I can see how increased memory latency hurts performance, and it’s unclear what the minimum random latency is at different CL settings and speeds on the Intel side. Also there’s a slight single digit ns penalty to sharing memory across units, a concept the comparable Intel parts don’t have, if I’m reading this right.

That said, the X570 chipset has PCIe 4.0 with improved power management to match, even at the ITX end. But PCIe 4 will likely go through implementation improvements and right now is only useful for storage in really fast Raid configurations, 15GB/sec performance from 4 drives has been demonstrated at a relatively cheap cost, comparable to high end commodity NVMe PCI 3 storage.

I wish it were obvious which part was “best” but different implementations lead to different optimizations/costs/benefits...

[snvzz]

Memory latency is one metric out of many.

For memory latency to matter, you need the worst case scenario to play out, which is a miss on all caches.

For cache to be made entirely irrelevant in performance, you'd need a situation where every access is a cache miss.

Yet even a pattern of completely random memory accesses will hit cache once in a while. And even then, a completely random access pattern is absolutely in disconnect with real world applications.

Thus, performance is not determined by memory latency. It is only a factor. And latency has actually improved, like other metrics, when compared to previous generations.

In short, wait for benchmarks. Just some three hours left for NDA lift.

[lstamour]

True, and the benchmarks told a very different story for Ryzen 3700 and 3900, that for most of these workloads, the gains from the extra cores far outweigh anything else including tiny RAM timing differences. The tests I saw ran with 3600 speed RAM though, for both.

[lstamour]

A very interesting article is https://www.pcworld.com/article/3298859/how-memory-bandwidth... which brings up Linux vs Windows, and compares the slightly older ThreadRipper 2nd gen to the 7th gen i9 part. Which means it’s possible the i9 outperforms the Zen 2 parts still, if random access memory is required and you’re on Windows where the difference is more apparent...