Will dual channel help Ryzen 7 performance?

[imrazor]

So I bought a Dell Inspiron 5675 with a Ryzen 7 and RX 580. Benchmarks (Fire Strike and Time Spy) are about 15% higher than my old gaming rig (3570K @ 4.2Ghz + GTX 970). However, Assassin's Creed Origins still gets about 45 fps on Medium settings @ 1080p during benchmark runs. That's pretty much the same as my old box, though it is noticeably smoother on the Ryzen. Why am I not seeing a 15% higher frame rate on the Ryzen?

In trying to diagnose this I've noticed a few things. Dell, in their infinite wisdom, decided to put in a single stick of DDR4-2400 in the PC. Would getting another 16GB stick help? How about 3200GHz RAM? To my surprise, Dell used the X370 chipset in the Inspiron 5675. I was expecting a B350 chipset, so maybe this will support higher RAM speeds ...?

I've also noticed some dips in GPU utilization when running the benchmark, down to as low as 20%. In addition, the 12 threads that the game are using are typically between 50% and 75% utilization.

So should I invest another $200 in a stick of DDR4-2400? Or do you think dropping my old 970 into the new rig would help?

P.S. I know this system is not that much faster in gaming than my old rig, but I wanted the extra cores for virtualization and something that could be patched against Meltdown/Spectre.

 

[CountMike]

Yes, my tests show definite improvement with dual channel, fast RAM and low latency. Problem is with games that don't use CPU, RAM and GPU equally but in general properly set up RAM has at least some effect.
If you are going to invest in RAM, best would be to invest in 2 x 8GB of faster RAM (3000 -3200MHz), Just dual channel of same (2400MHz) is going to give only very marginal results in general.

 

[imrazor]

So bad news. It looks like the Dell maxes out at 2666 Mhz, and it can't use XMP profiles. The speed has to be programmed in as a JEDEC speed into the SPD. See here: https://www.dell.com/community/Desktops-General/Fastest-Memory-for-Inspiron-Gaming-Desktop-5675/td-p/5127755/page/2 . Ryzen Master can't control the RAM clocks on this PC, though I can overclock the CPU.

I doubt I'd see a big improvement jumping from 2400 to 2666. I really want 32GB of RAM for some of my virtualization experiments. Given that, I think my best bet is to go ahead and double what I've got. I'm just not sure how much it'll help.

 

[CountMike]

Well, if you really need 32GB it's most probably going to hit a ceiling at 2400MHz anyway and as I said, in real work you'd get a very little just because of dual channel. Without XMP (usually called "DOCP" with AMD system) there would be a lot of fiddling to get it any faster. For best results, try getting exactly same RAM stick as you already have.

 

[imrazor]

After further testing it seems the problem is not with Ryzen, but rather the fact that Ubisoft hates Radeon GPUs.

I swapped out the RX 580 for my old GTX 970 and gave it a mild overclock - enough to nearly match the reference 580 in benchmarks. The difference in AC Origins was remarkable even though the benchmarks were nearly the same. At Very Low I get 69 fps, Medium nets 56 fps, and at Very High I get 49 fps. With the RX 580 I get 51 fps at Very Low, 45 fps at Medium, and Very High is 42 fps. Nutso...

 

[imrazor]

OK, more news. Apparently Dell has been re-badging RX 470s as 570s and and 480s as 580s in the Inspiron 5675. See here: https://www.dell.com/community/Desktops-General/Inspiron-5675-Desktop-NVME-M-2-slot-speed/m-p/5172495#M1029407

So it's not just Ubisoft hating on Radeons, it's also due to the fact that Dell is playing shady tricks with re-badged RX 480s. Technically, they can get away with it because AMD just gives OEM reference guidelines on clock speed, power consumption, etc., but it's up to the OEM to implement specific speeds.

There are a couple of other sketchy 'features' in the 5675. The two x16 slots actually run at x8 ( https://www.dell.com/community/Desktops-General/Inspiron-5675-motherboard-PCIe-slots/m-p/5171757#M1029192 ) and the NVME m.2 slot runs at PCIe Gen 2 speeds (effectively half speed, see here https://www.dell.com/community/Desktops-General/Inspiron-5675-Desktop-NVME-M-2-slot-speed/m-p/5172495#M1029407 ). Dell cut a lot of corners in this desktop...

 

[imrazor]

To get back on topic, this video shows a potentially huge difference between single and dual channel RAM, depending on the game and detail level.

https://www.youtube.com/watch?time_continue=517&v=u827fdCOCao