Vega 56 crossfire extreme flickering

[vibbelito]

I'm having a weird problem with my crossfire setup where it causes the games to flash/flicker like crazy almost causing an epilepsy seizure. The flickering change based on the refresh rate I set. This happens for instance in GTA V which is a game known for working well with crossfire. It also happens in other games that try to use both GPU's. It's almost like there's a problem with the picture synchronization/ blanking. I send the picture over HDMI and have tried both a TV and a projector with the same results.

I bought the cards from a guy at work for 200usd each and he has been running them flawlessly in crossfire. Both cards work on their own in both PCIe slots. I have tried two driver versions that were available on AMDs website with the same result.

 

My setup is:

GPU 1 - Sapphire AMD RX Vega 56 with 64 bios

GPU 2 - Sapphire AMD RX Vega 56 with 64 bios

Latest amd drivers.

CPU - AMD FX8350

MB - ASUS M5A97 R2.0

RAM - corsair vengeance ddr3 1600mhz 3x4gb 12gb

PSU - corsair CX850m

OS - windows 10 on a 240gb SSD

Games on a 7200rpm 500gb HDD

 

See this video of the problem. It is only visible in game and any overlays don't flicker.

 

 

[SavageNeo]

Sli and crossfire are pretty dead by now. You can have better fps, but worse latency.

[vibbelito]

5 minutes ago, SavageNeo said:

Sli and crossfire are pretty dead by now. You can have better fps, but worse latency.

That's not what I asked. I'm not interested in answers just telling me to sell the cards and get a single card instead. I mainly play games that support crossfire so this is a good option for me so it's out of question getting a more expensive single card that will give me worse performance.

[Juular]

This PSU isn't nearly enough for two Vega 56's that quite possiby an issue here.

[Juular]

One Vega 56 draws almost 400W, that's a bit higher with 64's BIOS and double that with two of them, now that's average power draw, it's recommended to have some headroom for GPUs this powerful, around 15-20% i'd say. Now AMD FX8350 draws around 250W in stress tests and a just bit less in games (it's not very power efficient CPU) so you need another 300W minimum for the CPU and other PC components. That makes minimum power requirements for around 1.3-1.4kW, you're running your PSU at the limits, i'm quite surprised it didn't trip on all this stuff already. Or maybe it did ? Were there any restarts ?

[vibbelito]

5 minutes ago, Juular said:

This PSU isn't nearly enough for two Vega 56's that quite possiby an issue here.

I have been thinking about that to but that would probably cause either one of the cards to shut down or crash the pc. The guy I bought them from was running them with a 650W PSU without any problems.

 

Overclocked one card can reach about 270W under full load and that would only reach 540W combined which leaves 310W for the rest of the system.

and when in power saving mode one rarely goes over 200W

[Juular]

2 minutes ago, vibbelito said:

I have been thinking about that to but that would probably cause either one of the cards to shut down or crash the pc. The guy I bought them from was running them with a 650W PSU without any problems.

 

Overclocked one card can reach about 270W under full load and that would only reach 540W combined which leaves 310W for the rest of the system.

and when in power saving mode one rarely goes over 200W

It's not about power consumption only, that's quite good quality PSU but it's not a good choice for two 400W GPUs even if there's enough power.

[vibbelito]

2 minutes ago, Juular said:

One Vega 56 draws almost 400W, that's a bit higher with 64's BIOS and double that with two of them, now that's average power draw, it's recommended to have some headroom for GPUs this powerful, around 15-20% i'd say. Now AMD FX8350 draws around 250W in stress tests and a just bit less in games (it's not very power efficient CPU) so you need another 300W minimum for the CPU and other PC components. That makes minimum power requirements for around 1.3-1.4kW, you're running your PSU at the limits, i'm quite surprised it didn't trip on all this stuff already. Or may it did ? Were there any restarts ?

I think Vega 64 bios on air is limited to 300W maximum. I could hook up the pc to a power meter to measure total system draw.

[191x7]

The motherboard has a single PCI-E 2.0 x16 slot, the other one is a full size slot (x16) but only with 4 lanes (x4).

That's the first part of the problem. 

 

The second part of the problem is the CX PSU. Weak on the 12V rails for the combo of two RX Vega 56 cards paired with FX "8-core".

 

The third part of the problem is the CPU bottlenecking the GPU system. An FX "8-core" is a huge bottleneck for a single RX Vega 56, not to mention two of them.

 

Your performance would be better if you'd just remove the second card.

That would remove the PCI-lanes discrepancy, the PSU power issues and since the CPU can't feed a single vega56 there would be no performance loss.

[Juular]

Just now, 191x7 said:

Your performance would be better if you'd just remove the second card.

Yup, that'a a cheap fix. Or just sell that room heater of PC and get smth power efficient.

[Juular]

You could've bought a new RX5700 XT instead of them (or RX5700 and flash it with -XT BIOS), it would've been a bit slower in Crossfire-friendly games but it will be faster in other and it's way more power efficient, and sell that AMD construction machinery CPU and get R5 3600(X). That PSU will be okay for this config but i'd replace it too with smth like 550\650W Corsair RMx \ Bitfenix Formula\Whisper \ Enermax Revolution DF.

[191x7]

1 minute ago, Juular said:

Yup, that'a a cheap fix. Or just sell that room heater of PC and get smth power efficient.

Also, the issues would be gone. It's that his CPU can't keep up with the frame pacing.

[GoldenLag]

38 minutes ago, Juular said:

This PSU isn't nearly enough for two Vega 56's that quite possiby an issue here.

PSU is enough. And the quality of it is fine. Probably does have some coilwine. 

 

 

[Juular]

22 minutes ago, GoldenLag said:

PSU is enough. And the quality of it is fine. Probably does have some coilwine. 

 

 

200-250W from the CPU + 50W system + 2x300W average power draw on GPU with 370W peaks, that's already 850W on average with 1050W peaks, OCP\OPP probably set a bit higher anyway but you don't want to push it just because it can. And i'd recommend multi-rail PSU even with one 300W GPU, not to say two of them, but even single-rail 1000\1200W PSU will be way more appropriate here.

[vibbelito]

48 minutes ago, Juular said:

It's not about power consumption only, that's quite good quality PSU but it's not a good choice for two 400W GPUs even if there's enough power.

I bought that PSU planning to crossfire 2 Radeon HD 7970 a few years back but once I got a second gpu it was killed instantly by a faulty crossfire bridge.

[GoldenLag]

2 minutes ago, Juular said:

200-250W from the CPU + 50W system + 2x300W average power draw on GPU with 370W peaks, that's already 850W on average with 1050W peaks, OCP probably set a bit higher anyway but you don't want to push it because it can. And i'd recommend multi-rail PSU even with one 300W GPU, not to say two of them.

Thats assuming full load. Something that you dont see with crossfire. 

 

And wouldnt point to the issues that he sees. 

 

And PSUs can run 20% above their rated wattage without shutting down. Tho not recommended. 

 

And OP isnt experiencing PSU shutdown. 

[Juular]

6 minutes ago, GoldenLag said:

And OP isnt experiencing PSU shutdown. 

He might experience GPU instability because of higher ripple, that's still unlikely because it might've affected both GPUs then but who knows how how long previous owner of this room heater has been running it like this, at 100%+ load, it may have damaged PSU and\or GPU VRM. I'm still more inclined to software causes of this issue and general inbalanced config but still, this PSU needs to be replaced if they plan to keep running crossfire with 2x300W GPUs.

[vibbelito]

47 minutes ago, 191x7 said:

The motherboard has a single PCI-E 2.0 x16 slot, the other one is a full size slot (x16) but only with 4 lanes (x4).

That's the first part of the problem. 

 

The second part of the problem is the CX PSU. Weak on the 12V rails for the combo of two RX Vega 56 cards paired with FX "8-core".

 

The third part of the problem is the CPU bottlenecking the GPU system. An FX "8-core" is a huge bottleneck for a single RX Vega 56, not to mention two of them.

 

Your performance would be better if you'd just remove the second card.

That would remove the PCI-lanes discrepancy, the PSU power issues and since the CPU can't feed a single vega56 there would be no performance loss.

Yeah I was thinking about those PCIe lanes being a possible problem with them only being gen 2 and one of them being x4. I could see if lowering the resolution solves it. That should take care of any potential bandwidth problem. 

 

And yes I have noted a huge bottleneck by the CPU running even one card. And with both cards working they are only utilized max 50% with pretty much the same fps. 

I will be switching over to a i7-4770 in the coming week. Which could still bottleneck but not as much. 

[Juular]

See, OP, do this occur in all\most games or only in GTA V ? Did you try running only one of the GPUs to see if they're stable one by one ?

[GoldenLag]

Just now, Juular said:

He might experience GPU instability because of higher ripple, that's still unlikely because it might've affected both GPUs then but who knows how how long previous owner of this room heater has been running it like this, at 100%+ load, it may have damaged PSU and\or GPU VRM.

Dead VRM would lead to overheatinh and throttingling. 

 

HBM2 issues are possible tho unlikely. 

 

And 12v ripple while could lead to instability. Its more to do with component harm. And the cxm isnt a known bad PSU in terms of overload ripple. 

[Juular]

5 minutes ago, vibbelito said:

I will be switching over to a i7-4770 in the coming week. Which could still bottleneck but not as much. 

Yep, that's still not much of an upgrade in comparison with modern CPUs but it's a massive upgrade from Bulldozer. Althrough, it would raise GPU utilization and power consumption even further and can lead to PSU tripping on it, if you didn't run it at it's maximum capabilities now you definitely will then.

[vibbelito]

38 minutes ago, GoldenLag said:

PSU is enough. And the quality of it is fine. Probably does have some coilwine. 

 

 

I actually don't get any noticeable coilwhine. Py previous 500w psu however you can think will explode from its whine under load. 

[vibbelito]

17 minutes ago, GoldenLag said:

And OP isnt experiencing PSU shutdown. 

Yeah I haven't seen any crashes at all 

[vibbelito]

13 minutes ago, Juular said:

He might experience GPU instability because of higher ripple, that's still unlikely because it might've affected both GPUs then but who knows how how long previous owner of this room heater has been running it like this, at 100%+ load, it may have damaged PSU and\or GPU VRM. I'm still more inclined to software causes of this issue and general inbalanced config but still, this PSU needs to be replaced if they plan to keep running crossfire with 2x300W GPUs.

The gpu actually has very good vrm capable of over 400w. And has Samsung HBM2 memory so very high quality there. The previous owner have been running them undervolted playing mostly world of tanks in 4k.

I said the wrong thing earlier, he has a corsair something850i psu.

He have maybe 20 more of these GPU's that he is mining with so he even gave me 3 months warranty on them. These 2 particular ones haven't been mined with however. 

[Juular]

5 minutes ago, vibbelito said:

I said the wrong thing earlier, he has a corsair something850i psu.

Corsair RMi\HXi\AXi 850W is a bit more appropriate PSU for this, being multi-rail i'm at least a bit more confident that it will not explode would one of GPUs fail, it has more sophisticated protections overall and higher efficiency so it'll run cooler at the same load so it's lifetime will be longer. Corsair CXm is like the cheapest PSU that could handle this config at all, that doesn't mean it's okay for it tho.