Vega 56 crossfire extreme flickering

[Tristerin]

2 minutes ago, vibbelito said:

You are probably correct in that these fast cards aren't able to communicate fast enough with each other over that PCIe gen 2 x4 slot. I have ran a few tests wit the superposition benchmark and by the looks of it the flashing is much less visible when running a 720p test and when running a 4k test the screen is more black than anything else which to me indicates that it isn't able to synchronize the frames between the two cards. 

I will do one final test today and that is to swap out the FX-8350 and MB with an i7-2600 with DELL oem MB. Which I guess also only have a x4 slot. But it's worth a try.

check the mobo OEM manual to see how the slots are oriented in that mobo, if using SATA ports kills PCIE bandwidth on slots etc, should answer questions early on.

[vibbelito]

18 minutes ago, Tristerin said:

check the mobo OEM manual to see how the slots are oriented in that mobo, if using SATA ports kills PCIE bandwidth on slots etc, should answer questions early on.

It's a Dell OptiPlex 790 Mini-Tower and it seems like it also uses one 16x slot and one 16x slot wired up as a 4x slot whilst being PCIe gen 2

 

See attached pdf

optiplex-790_owner's manual_en-us.pdf

[vibbelito]

Running the superposition benchmark at 8k crashes the PC for some reason. 

[tankyx]

This PC is responsible for global warming.

Sell it, take something better.

[Tristerin]

I cant even bring myself to sell someone my FX rig because I feel like I would be raping them unless it was free. 

[191x7]

Selling the old FXium (because it went the way of the dinosaurs like the pentium) and one of the Vega cards would allow you to get a decent Ryzen capable of feeding a Vega 56.

Guess what - there wouldn't be any issues, you would have at least double the performance  in games compared to now, your power bill would be lowered and this thread would end.

Stop pairing two mid-range cards with a platform that's low end so hard it low ends the lowest low end of the modern day (FX, Sandy/ivy/haswell, anything with 4 cores and less that 8 modern threads).

 

My friend, the FX 8350 clocked to 4.5 GHz can't even prerender enough for an RX 560 in most modern games. And a trash i7 like the 2600k/3770k/4770k/4790k can't do a lot better, the top for those would be RX 570.

Modern games are modern.

[vibbelito]

11 minutes ago, 191x7 said:

Selling the old FXium (because it went the way of the dinosaurs like the pentium) and one of the Vega cards would allow you to get a decent Ryzen capable of feeding a Vega 56.

Guess what - there wouldn't be any issues, you would have at least double the performance  in games compared to now, your power bill would be lowered and this thread would end.

Stop pairing two mid-range cards with a platform that's low end so hard it low ends the lowest low end of the modern day (FX, Sandy/ivy/haswell, anything with 4 cores and less that 8 modern threads).

 

My friend, the FX 8350 clocked to 4.5 GHz can't even prerender enough for an RX 560 in most modern games. And a trash i7 like the 2600k/3770k/4770k/4790k can't do a lot better, the top for those would be RX 570.

Modern games are modern.

Well do you have any suggestion on what the lowest tier AMD CPU is that wouldn't be able to bottleneck dual Vega cards then?

Thinking about getting a ryzen ryzen 9 3900x or possibly a ryzen 9 3950x if that isn't way to overkill for crossfired Vega 56. 

[Zando_]

2 hours ago, Tristerin said:

x4 slot likely the culprit - I would assume you need x8 x8 for this to run smoothly in crossfire.

Ooooooooo yeah that'd be an oof and highly likely to be why it's being funky. On Nvidia, SLI won't even run at all without x8/x8, lower AMD GPUs in crossfire might be okay with x4, but V56s are pretty powerful. 

 

9 minutes ago, vibbelito said:

Well do you have any suggestion on what the lowest tier AMD CPU is that wouldn't be able to bottleneck dual Vega cards then?

Thinking about getting a ryzen ryzen 9 3900x or possibly a ryzen 9 3950x if that isn't way to overkill for crossfired Vega 56. 

If you wanna go Zen 2, the R5 3600 would be excellent. About on par with a stock i7 8700K. The 3700X would be excellent as well, 3900X is quite a price hike for not much perf difference in gaming. 

[vibbelito]

Well I put up a nice little test bench based on the Dell optiplex 790 motherboard with an i7-2600 and 8gb RAM. And running everything of an 120gb ssd with a fresh install of windows 10.

 

I started out with an AMD radeon HD5870 to compare performance increase and bottlenecking, ran some benchmarks and moved on to an AMD Radeon HD7970, installed the latest drivers and ran the same benchmarks and saw pretty much a doubling in performance. Then when I moved on to the Vega 56 where the first card crashed on boot so I switched to the other one which booted after some tries. 

But everything was running extremely sluggish and for some reason the pc was taxing the GPU 100% most of the times while idling. So I downloaded and installed the latest drivers which actually was the same as the ones for the 7970. But the problem persisted and the screen went black a few times. I then preceded with trying the benchmark again but it crashed on the lowest 720p settings. 

(Yes I play Half-Life 2 on this pc, don't you need dual Vega56 for that?)

 

So for some reason this old pc can't handle this newish GPU due to something being incompatible. 

 

So I guess well have to wait until I get something newer to see if we can get to the bottom of exactly what's causing the flickering. 

[191x7]

20 hours ago, vibbelito said:

Well do you have any suggestion on what the lowest tier AMD CPU is that wouldn't be able to bottleneck dual Vega cards then?

Thinking about getting a ryzen ryzen 9 3900x or possibly a ryzen 9 3950x if that isn't way to overkill for crossfired Vega 56. 

 

For dual vega 56 on 1080p - even the i9 9900K would bottleneck in some instances, but i7 9700K or 8700K would do fine. On the Zen side it would be a 3700X and up.

On 1440p the're some difference, the Ryzen 5 3600, 3600X or Ryzen 7 2700(x) would probably do fine. Or the i7-s and i9-s.

On 4K, something like Ryzen 1600X, 2600, 2600X or Intel i5 8400f, 8600K, 9600K.

For a single Vega56 on 1080p I'd recommend the Ryzen 2600 or 2600X as the lowest, but higher cores or newer cores would be better.

[vibbelito]

19 hours ago, 191x7 said:

 

For dual vega 56 on 1080p - even the i9 9900K would bottleneck in some instances, but i7 9700K or 8700K would do fine. On the Zen side it would be a 3700X and up.

On 1440p the're some difference, the Ryzen 5 3600, 3600X or Ryzen 7 2700(x) would probably do fine. Or the i7-s and i9-s.

On 4K, something like Ryzen 1600X, 2600, 2600X or Intel i5 8400f, 8600K, 9600K.

For a single Vega56 on 1080p I'd recommend the Ryzen 2600 or 2600X as the lowest, but higher cores or newer cores would be better.

This seems to check out so now the decision lies in deciding between going for intel platform (i7-9700k/ i9-9900k) or AMD platform (ryzen 7 3700x / ryzen 9 3900x) considering I do sometimes do some photo and video editing. The FX-8350 was fine but it always left me craving for more raw cpu power when editing/rendering.

 

Anyway the decision will probably boil down to what PCIe generation and speed I will ultimately need to never ever having to see this god awful headec causing flashing. I think the intel motherboards offer up to dual PCIe gen 3 x16 slots without slowing them down. 

 

But AMD has PCIe gen 4 on the latest motherboards and gen 3 on the older ones but I can't seem to find anyone with dual PCIe 3.0 x16 slots. It always seem to be that one either runs at x8 speed all the time or that if both slots are used, that they both run at x8 speeds. 

 

What should I go for then to allow these cards to run at full potential taking everything in consideration.

 

And yes I might upgrade that 850w psu as well then to allow for some overclocking and not having it run at the peak of what it's capable of. 

[vibbelito]

Except for normal gaming and some video editing I also plan to run Valve index VR on the system if that makes any difference.

 

I am also for fun considering a motherboard that allows for Quad-Crossfirex to run 4 of those power hungry Vega 56 GPUs' but I don't think scaling would be particularly good beyond 2 of them.

[191x7]

4 hours ago, vibbelito said:

Except for normal gaming and some video editing I also plan to run Valve index VR on the system if that makes any difference.

 

I am also for fun considering a motherboard that allows for Quad-Crossfirex to run 4 of those power hungry Vega 56 GPUs' but I don't think scaling would be particularly good beyond 2 of them.

Even scaling with two isn't that particularly good.

[vibbelito]

After hooking up the 40$ dell optiplex 9020 with an i7-4790 and 24gb ram. I connected the two Vega 56, one to a PCIe 3.0 x16 and the second to a x16 slot running at x4 speeds the flickering have now been reduced to specific textures for some reason.

I run the exact same SSD that was in the FX-8350 system and the exact same drivers so the problem must be that the FX-8350 platform wasn't up to the task

[vibbelito]

Just thought that I should add that according to my motherboard box it does support crossfire. 

But that may well be because back then the crossfire wasn't communicating purely over the PCIe link. And instead used a separate crossfire bridge.