AMD Threadripper 1950X RAM problem?

[Jiri.Matys]

Hi,

I have some informations about newest AMD 1950X, that it cant allocate whole RAM while rendering. Probably because this procesor contain two procesors in one package, it allocate only half memory for one internal procesor. So if I have let says 64GB of RAM, when system use half of it, only 32GB, then start to swap. Is this a true please?

Thank you.

[Alex_M]

Never heard of this. Where did you get this information from, can you please post link or show evidence? Do you think they would release a processor that can't allocate your RAM properly? Sounds like a rumor to me or you misunderstood. The two dies in Threadripper, just like in Epyc (which has 4 dies), are interconnected and can freely talk to each other and allocate all the RAM they need thanks to Infinity Fabric and the MCM (multi chip module) design.

Check out these videos and you'll get a better idea of how Threadripper and Epyc work:

[Jiri.Matys]

I dont missunderstood.

My friend watched rendering on a new computer AMD 1950X with 64GB of RAM and after 32GB was full computer slow down and swap to HDD.

I just wanna ask somebody with this AMD if anybody notice this problem.

Its something like dual xeons which has already been discussed here many times. But for me I think there was some problem with AMD computer because its look weird to me. I just wanna know other opinion, thank you.

[Alex_M]

Ok, I'll try to test this on my 1950X and share my findings in this thread.

[Vsha]

Same problem here with 1950x, after filling 50% RAM during rendering, system starts to behave like he is out of memory :/

[Alex_M]

I've just tested this by deliberately making the scene heavy (no instanced objects, lots of unnecessary displacements etc.). Well... no such problem here. For me it allocates as much RAM as it needs. Please see the screenshots below. You can see that Max is able to allocate quite a lot more than 32 GB RAM and there's no disk swap activity. My render or PC didn't slow down after surpassing 32GB either.

Maybe there are some settings in Windows and/or BIOS that you've changed to cause this behavior? Maybe you can also check if your RAM was installed properly in the motherboard? Also, does it run in quad channel mode? It should for optimal performance. Can you post some screenshots/videos of this behavior? That would be interesting to see.

[Vsha]

Hi,
I did another test on my work PC, tried to fill the RAM with vraydisplacement. Now it can allocate whole 64GB RAM (4*16 GB quad channel). But in some rare cases (i need to find in which one ), i can't get over 32GB of RAM.
MB : Gigabyte X399 Aorus Gaming 7(latest bios version).

Marcel

[Alex_M]

That's interesting. In the first image (the birds eye view) I haven't used any displacements and it still uses as much RAM as it needs. If you find a case where it can't use more than 32 GB and starts swapping to disk, just send me the scene (if possible, of course) and I'll test it on my system too.

[Jiri.Matys]

Interesting, so there is some problem with this CPU. The questin is what couses this problem. Vsha, if you can share problematic scene with Alex to test it, it would be helpful.

[urbanite]

It would be great to hear for people who have already bought this cpu as I am about to buy one and this could be deal breaker for me.

[Vsha]

Can't share scenes, because NDA. But I am testing different heavy scenes which i modified to allocate whole RAM (volumetrics, ornatrix, forest pack, turbosmooth x8 ), All are working fine.
I changed some settings in BIOS and windows a few days ago. Maybe I found the solution and didn't know about it until now - i didn't need more than 32GB RAM.
Result of testing : there was a problem with RAM allocation in a new untouched workstation, but it can be fixed with some updates and magic.

[Alex_M]

It would be great to hear for people who have already bought this cpu as I am about to buy one and this could be deal breaker for me.

Well, there are 2 machines here with Threadripper 1950X and 64 GB RAM that we bought so I can test this. In the few tests I did, I haven't seen such problems. As you can see by the screenshots I posted above, 1950X is able to use a lot more than 32 GB RAM just fine (why shouldn't it?). Please send me any scenes that you think might have this problem and I'll test it on my 1950X. Frankly, this is the first time I hear 1950X not being able to use more than 32 GB RAM.

Please see attached another scene I've just tested. All trees and shrubs are unique non-instanced non-proxy objects to make it as heavy as I can. Notice the "Memory" and how it shows 54.2 GB RAM being used. Also, disk activity is basically zero so no swapping is happening either.

Can't share scenes, because NDA. But I am testing different heavy scenes which i modified to allocate whole RAM (volumetrics, ornatrix, forest pack, turbosmooth x8 ), All are working fine.
I changed some settings in BIOS and windows a few days ago. Maybe I found the solution and didn't know about it until now - i didn't need more than 32GB RAM.
Result of testing : there was a problem with RAM allocation in a new untouched workstation, but it can be fixed with some updates and magic.

Fair enough. Good to hear you managed to solve it. On the two 1950X machines here we just installed the latest BIOS and left it basically at default (except for OC'ing the CPU) and then we installed Windows 10 and the AMD drivers for Threadripper.

Pro tip - if you have 64 GB on 8 sticks of RAM instead of 4 sticks and they are faster than 2800-2900 Mhz, you are putting more stress on the IMC and you might not be able to boot properly or get blue screens, restarts etc. You'll need to decrease the speed of your RAM to 2900-2800 Mhz to get a stable system. This is what happened on the machines here when we used 8 sticks of 64GB 3200 Mhz RAM. If I use only 4 sticks of RAM (32 GB) I am able to run it stable at 3400-3600 Mhz just fine. Also, always check if your RAM kit is on the QVL list of your motherboard. Here's an example with Asrock X399 Taichi.

[Jiri.Matys]

I dont have AMD, I just heard from my friend there is some problem. Good its fine, thanks.

[urbanite]

Alex, have you tested how RAM different clock reflect on rendering in VRay? Somebody have mentioned that in Corona you can gain 10% just by using higher clock RAM (2600 vr 3200).

[Alex_M]

Ok, I might test this.