Nvidia/AMD asynchronous stuff, whats happening?

[Heizu]

Hey guys,

So what exactly is going on between nvidia and asynchronous computation??

Ive heard bits and pieces from posts but nothing really informative.

Thanks for any info!

[Sakkura]

https://www.reddit.com/r/pcgaming/comments/3j1916/get_your_popcorn_ready_nv_gpus_do_not_support/

 

Simplified explanation:

 

 

Think of traffic flow moving from A->B.

NV GPUs: Has 1 road, with 1 lane for Cars (Graphics) and 32 lanes for Trucks (Compute).

But it cannot have both Cars and Trucks on the road at the same time. If the road is being used by Cars, Trucks have to wait in queue until all the Cars are cleared, then they can enter. This is the context switch that programmers refer to. It has a performance penalty.

AMD GCN GPUs: Has 1 Road (CP; Command Processor) with 1 lane for Cars & Trucks. Has an EXTRA 8 Roads (ACEs; Asynchronous Compute Engines) with 8 lanes each (64 total) for Trucks only.

So Cars and Truck can move freely, at the same time towards their destination, in parallel, asynchronously, Trucks through the ACEs, Cars through the CP. There is no context switch required.

NV's design is good for DX11, because DX11 can ONLY use 1 Road, period. GCN's ACEs are doing nothing in DX11, the extra roads are inaccessible/closed. DX12 opens all the roads.

[Fulgrim]

Hey guys,

So what exactly is going on between nvidia and asynchronous computation??

Ive heard bits and pieces from posts but nothing really informative.

Thanks for any info!

Nvidia oversight; they didn't bother implementing something because the latest DirectX at the time didn't benefit from it. Now that decision has come back to bite them in the arse. And they've tried to underhandedly convince Oxide to disable features which benefit from Asynchronous Compute/Shaders to get Nvidia's performance up in the benchmarks, and lower the performance of AMD cards in DirectX 12.

 

(Asynchronous compute/shaders is something only AMD cards support right now)

[Heizu]

https://www.reddit.com/r/pcgaming/comments/3j1916/get_your_popcorn_ready_nv_gpus_do_not_support/

 

Simplified explanation:

hmm interesting read, guess i might have to switch teams .-. r9 380 here i come....

[Fulgrim]

hmm interesting read, guess i might have to switch teams .-. r9 380 here i come....

I'd wait for AMD's second generation HBM cards to come out tbh. It'll be a while before most new titles use DirectX 12.

[Heizu]

I'd wait for AMD's second generation HBM cards to come out tbh. It'll be a while before most new titles use DirectX 12.

fair point probably will do, that literally just picked up a gtx 960 a month ago>.>

[MichaelTechTalk]

In an article, Mark Cerny mentioned that developers will be taking huge advantage of this architecture for the PS4 in which he also stated that PC will inherit those benefits for those with supported GPUs. The PS4 has a 7870 GPU.

[Sakkura]

In an article, Mark Cerny mentioned that developers will be taking huge advantage of this architecture for the PS4 in which he also stated that PC will inherit those benefits for those with supported GPUs. The PS4 has a 7870 GPU.

 

The PS4 GPU is smaller/weaker than the fully enabled Pitcairn in the 7870. 1152 shaders, halfway between the 7870 and 7850 (1280 and 1024).

[MichaelTechTalk]

The PS4 GPU is smaller/weaker than the fully enabled Pitcairn in the 7870. 1152 shaders, halfway between the 7870 and 7850 (1280 and 1024).

I'm aware that the PS4 has a cut down version of the 7870 by disabling 2 of its Compute Units (-128 shaders) and bring its down to 1024. Mark was referring to the PS4s 8 ACE's that will be taken advantage of which will add things to the screen never seen before in gaming.