CPU Choice for Multi User Setup

[Chrysaetos_]

     Hey guys, my roommates and I have been inspired by Linus' 7 Gamers build to look into building a single system for the three of us. We're all gamers, and one of us would like to stream as well. We're trying to decide on a CPU and are hoping y'all can help.

     This build is likely to happen far enough out that our graphics cards will be next gen, but for now we're parting them out as 2x 2070 Supers and 1x 2080 ti. We also have it parted out so we each have an M.2 NVMe drive. I'll link the full parts list, but keep in mind it's essentially a first draft.

     Our choices for CPU are between a Threadripper 2950X and a Ryzen 9 3950X. We are leaning towards the Threadripper because of the 64 PCIe lanes, but we aren't sure that that will matter because the Ryzen's lanes are 4th gen. I've found a report, linked below, that a 2080ti has little to no performance loss in PCIe 3.0 x8 compared to x16. My understanding is that 3.0 x8 is equivalent to 4.0 x4. Therefore, could we run the graphics cards in x4 with the Ryzen? And would we still have enough lanes for the SSDs? The SSDs can be SATA if need be but would be nice to know. If we can go with the Ryzen it would be preferred because of the single core performance gains over Threadripper.

 

Any help would be appreciated, thanks ^-^

 

2080ti PCIe impact

https://www.techpowerup.com/review/nvidia-geforce-rtx-2080-ti-pci-express-scaling

 

Parts List

https://pcpartpicker.com/list/XcMZrV

 

 

[Jurrunio]

Note that this will hurt performance comparing to 3 separate systems.

 

If you use the 3950X, two GPUs will run PCIe 3.0 x8 to the CPU while the other will run PCIe 3.0 x4 to the chipset, then the CPU (extra latency). 16 PCIe 4.0 lanes cannot be turned into 32 PCIe 3.0 lanes directly from the CPU, you'll need a proper PCIe transcoding chip (or whatever it's called, if it even exists) which motherboards dont have (and they add latency, bad for performance)

 

With 2950X, you'll take the hit in high frame rate gameplay due to older Zen's architecture. Also since you effectively only have 4/3 memory channels per system, it could very well do even worse than say, an R5 2600 in games per machine since that gets 2 memory channels per user

[Chrysaetos_]

I don't want to turn 16 lanes of 4.0 into 32 lanes of 3.0, I just want to know if I can set the GPUs to only use 4 lanes of PCIe 4.0 each, and if that will have anything larger than a minimal impact of performance.

[Jurrunio]

3 minutes ago, Chrysaetos_ said:

I don't want to turn 16 lanes of 4.0 into 32 lanes of 3.0, I just want to know if I can set the GPUs to only use 4 lanes of PCIe 4.0 each

20 series does not support PCIe 4

 

4 minutes ago, Chrysaetos_ said:

and if that will have anything larger than a minimal impact of performance.

yes, not so much PCIe (not with Threadripper for sure) but the CPU and memory.

[Chrysaetos_]

9 minutes ago, Jurrunio said:

20 series does not support PCIe 4

So if we waited till next gen cards, which from the sounds of things will have at least PCIe 4, and went with the Ryzen that should be fine? I get that it might be hard to say because we don't know anything about the next cards yet, but lets assume they're not a huge jump and they support 4.0. That should take care of CPU performance, right? I don't really know much about what I'm looking for with memory, this is all very new to me and I'm just starting to get into it. 

[Jurrunio]

2 minutes ago, Chrysaetos_ said:

So if we waited till next gen cards, which from the sounds of things will have at least PCIe 4, and went with the Ryzen that should be fine?

Stlll have problems with the board. I dont know which boards can do x8/x4/x4 setup on X570, though there is the Asus WS board that has a PLX chip and solves all problems with PCIe (at a high cost)

 

5 minutes ago, Chrysaetos_ said:

That should take care of CPU performance, right?

No, CPU performance and PCIe bandwidth are different metrics. With 16 cores spread to 3 users, you'll be getting 5 cores per user while even a lowly R5 3600 has 6 cores...

 

6 minutes ago, Chrysaetos_ said:

 I don't really know much about what I'm looking for with memory, this is all very new to me and I'm just starting to get into it. 

With the 3950X, you'll get 1/3 the transfer speed than you would with a single machine (same dual channel memory config), so even if you get 3x the capacity, performance still takes a hit especially when everyone starts pulling hard on the hardware

[Chrysaetos_]

2 minutes ago, NZgamer said:

I've read this thread and It's probably just a better idea to run seperate systems

Better because of the performance loss of doing it this way, or because it's easier and I clearly don't know what I'm doing. Cause I understand the second part, but figuring this out is the fun part and that's most of the reason I'd do this to begin with.

[Chrysaetos_]

12 minutes ago, Jurrunio said:

With the 3950X, you'll get 1/3 the transfer speed than you would with a single machine (same dual channel memory config), so even if you get 3x the capacity, performance still takes a hit especially when everyone starts pulling hard on the hardware

Idk that any of us are too concerned about losing a core given going this way with a 3950x is almost $400 cheaper than a similarly specced build, but I'll look into the RAM issue some more. Thanks for the help!

[Jurrunio]

5 minutes ago, Chrysaetos_ said:

a similarly specced build

as in, same board (which is completely unnecessary) same case same PSU? Of course.