Timespy crossfire

[Devil Djinn]

My crossfire setup doesnt work on timespy, only works 1 gpu.
running crimson 16.6.2.
2 x r9 280x
crossfire worked fine in firestrike, is this behavior normal?

[UL_Jarnis]

It uses Crossfire if it is enabled an supported by the GPU Driver (Linked-adapter Explicit Multi-GPU).

I must admit our test lab does not have HD 79xx/R9 28x multi-GPU setup to test as our HD 7990 failed a while ago, but there is nothing in the benchmark code that would make it not work.

It has been tested with...

R9 295X2 (so 2x R9 290)
2x Fury Nano
2x Radeon Pro Duo (so 4x Fury X)

...and it works perfectly fine.

[Devil Djinn]

i must of been mis informed. Was told dx12 multi gpu was up to developer rather than driver related, opps.
anyway, i upgraded my drivers to beta, and it still doesnt crossfire.
Crossfire works with all my other games i own, and scales quite well.
odd.

[UL_Jarnis]

Originally posted by Devil Djinn:

i must of been mis informed. Was told dx12 multi gpu was up to developer rather than driver related, opps.
anyway, i upgraded my drivers to beta, and it still doesnt crossfire.
Crossfire works with all my other games i own, and scales quite well.
odd.

Linked Multi-Adapter is kind of... halfway. It requires identical cards and some of the stuff related to initializing and choosing the GPUs that receive commands is handled by drivers. Once the actual rendering starts, then it is "pure DX12" in that the engine assigns work to all the available GPUs and driver has no say on any of that.

Considering a few other reports, I have a nagging feeling that latest AMD drivers for HD 79xx/R9 280 series does not support Linked Adapter Explicit Multi-GPU properly. In short, it presents to Time Spy only one GPU when asked to give all of them.

I guess I can ask our database guy to see if we have any multi-GPU results with this card in our database, that would pretty much settle it.

[HARVEY]

I have 7970 in crossfire and it worked fine score 4000+

[UL_Jarnis]

Originally posted by HARVEY:

I have 7970 in crossfire and it worked fine score 4000+

Just to make sure, which exact driver did you use?

[HARVEY]

16.6.2 i used,

[Devil Djinn]

really strange, guess it must be my system.
cant understand what it might be. running the same drivers too.

[Devil Djinn]

Originally posted by HARVEY:

I have 7970 in crossfire and it worked fine score 4000+

i get a similar score : http://www.3dmark.com/spy/60057
it says 2 gpu's, but the secondary runs at 0% load. Hwinfo + rivatuner.

[LBXZero]

By observation with my system, it only runs multiGPU for my 2 R9 390Xs when Crossfire is active. This tells me that it does not use DX12's multi-GPU mode when the GPUs are unlinked in the driver.

Read the technical manual. It is worded in contradiction. The manual explains explicit multi-adapter is the MDA mode, where as the LDA, despite listed as explicit, is actually implicit multi-adapter, letting the driver manage coordinating the GPUs.

False advertising.

[UL_Jarnis]

DX12 offers 3 modes

MDA
LDA Implicit
LDA Explicit

Time Spy uses LDA Explicit.

Driver does not manage work across GPUs. The engine does. The only limitation is that this mode works only with identical cards.

[LBXZero]

Double speak for "false explicit". Time Spy does not hold up as a true DX12 benchmark tool.

If the software is managing the GPUs, why does Time Spy require Crossfire to be enabled for my identical R9 390Xs to operate in linked mode? If they are explicitly being identified, then having the driver managed mode active should not matter for a pair of identical GPUs.

[UL_Jarnis]

Originally posted by LBXZero:

Double speak for "false explicit". Time Spy does not hold up as a true DX12 benchmark tool.

Implicit = Driver controls everything, like in DX11.
Explicit = Application controls multi-GPU

And you probably have no idea how complicated it is to support MDA so it actually shows any meaningful gains in true mixed setups (two considerably differently performing cards). A choice was made, based on what we expect games to support. So far DX12 games have either not supported multiGPU at all, or have used LDA. Ashes of Singularity is the only exception I can think of.

...also the number of people with one high end AMD and one high end NVIDIA card beyond press test labs is fairly close to zero, so MDA is a multiGPU mode with no user base.

[LBXZero]

Then explain why my pair of identical R9 390Xs require Crossfire to be enabled for "explicit" to identify them. Crossfire is the driver managing it.

If these 2 GPUs are being explicitly handled, then having Crossfire active or not should not influence the score. They are both as identical as possible.

It sounds like Futuremark took a shortcut to release a DX12 benchmark up to industry expectations. I do fully understand how complicated it would be to handle a true explicit mode between mix-matched GPUs, but what is being advertised is not what is being sold. I strongly advise the "explicit multiadapter support" be removed from the description, replaced with "LDA support", to be more accurate. Well, if the LDA support actually worked.

[UL_Jarnis]

DX12 supports only Explicit multi-GPU. Any implicit multi-GPU would be driver side special sauce (I do not think any support such a mode yet).

There are two Explicit multi-GPU modes available, MDA and LDA. Time Spy supports LDA. To run in LDA, you need the SLI/Crossfire to be on as that determines how many GPUs DX12 reports as available to the application for Linked-node use.

[LBXZero]

When I see "explicit Link", I see DX12 and the software detecting the GPUs and establishing links between matching cards. If the driver must be asked to establish a link, that means the driver can manage the link.

As the systeminfo shows, you don't need Crossfire or SLI active to detect the multiple GPUs. For software that targets a single GPU only, the driver creates the links and manages the linked adapters as a single GPU.

You don't need Crossfire and SLI to enumerate devices. The only reason for Crossfire and SLI to be active is to utilize the Crossfire and SLI bridges, but that means linked mode operations are being driver managed.

Overall, LDA is no less than a hybrid mode between implicit and explicit. The explicit LDA is a false mode made up for marketing purposes using doublespeak to cheat the consumers.