Dual vs Quad vs Six channel RAM real performance advantage?

[kingmax]

Hi. I'm building some new Corona oriented render nodes.

Does anyone know what performance impact would a dual vs quad channel RAM setup bring? Talking about a dual xeon system.
Anyone tried six channels?
I can't even find real-life benchmarks regarding 2133 vs 2400Mhz DDR4.

[Juraj]

It really depends on the architecture of the CPU platform. Corona does benefit from faster memory but it's only noticeable when the memory is the limiting factor for the CPU's performance.

I've run 2133 vs 2933 for my i9 7980XE, almost no difference in Corona rendering speed. Same difference in 2990WX amounted to quite a lot (37 vs 46 seconds ?). Both are quad-channel.

I thus don't think the six-channel for current Xeon platform (and x599 28core i9) will do much in favour of Corona rendering speed. Corona does favor somewhat the Intel platform though.

Anyway, current Xeons support only ECC memory and you really can't choose much there. Fastest seems to be 2400 and there isn't much price difference to 2133. Go with the faster unless you can get big price benefit in favour of slower. (Because slow 128 is still much better than fast 64GB).

[kingmax]

Thanks for the info. I can get hold on a pretty cheap DDR4 2133 ECC modules. I guessed too that on the intel platform RAM speed  really wouldn't matter that much in terms of performance. Since I'm building some "cheap" dual xeon systems as render nodes, I was going for 64GB machines as I rarely need more RAM than that. Problem is, the modules I can get my hands on are 16GB, so for a quad channel you should be getting 8 of them on a dual CPU system. Anyhow, as soon as I get one assembled I'll try to do some testing regarding RAM channels and speed and try to post the results.

[Juraj]

Yes, the channels required are always per cpu-socket, so 8 for dual-xeon system. But again, it doesn't make much of a difference to rendering load in Corona on Intel systems.