I haven't posted anything on my blog in ages! That's not good, so I am going to change that. Here is a tiny little test I did. It came about because I wanted to see if there were any major performance differences between running my Ryzen 9 3950X with 1 or 2 DIMMs per channel, at the same 3200 MHz C14-14-14-31 settings. If not, I was going to split up my 4x8 GB kit and upgrade the RAM in one of my WCG servers.
For a long time, I've always considered 2 DIMMs per channel to be the best memory solution for the 3950X, and to a lesser extent the 3900X - these two parts can likely put a lot of strain on memory parallelism within the RAM... The fact is that with two sticks per channel, you have a chance that the second DIMM is ready before the first is refreshed, and can take a read/write command without the UMC having to wait for the first (and only) DIMM to refresh.
This is the technical reason, but I wanted to see it for myself. I'll say it now, that I am lazy and it's 3 AM, so I only tested two games. Fortunately, one of those games - Ashes of the Singularity: Escalation - seems to have some pretty insane gains from having 2 DPC in the system. The other game, Far Cry New Dawn, saw basically no change in performance.
Well, it shot down my idea of splitting up the kit. I want the 3950X to have the best memory set up it can. So, I guess you want the results. I'll give you the results. So you shut your mouth!
I was a bit surprised, but the science checks out (did you read what I typed above?). You can see that when I tightened up the tRFC - a timing that controls how quickly the DIMM can refresh to accept a new command (Row Refresh) - the performance increases. What this tells me is that this game (which, by the way, uses a lot of RAM, and loads up all 16 cores pretty easily), is limited in some scenes by the speed at which the RAM can respond to a read/write request.
This makes sense to me, because the 3950X would theoretically generate twice the memory traffic as, say a 3700X, because you have twice as many cores/threads competing for that same, Dual-Channel memory controller. Of course, you could also just increase the ram frequency, it'd have the same effect along with reducing the tRFC absolute time (in ns). But if you're like me and are terrified of overclocking your RAM, 2 DPC seems like a good way to get around that limitation.
Well, or you could just need more RAM. Well, I used to need it, but I stopped using Adobe Premiere Rush as much lately, and that was the main application that would use the 32 GB of RAM.
That said, I'll keep it in there, because it makes me Happy.