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> No one is using the iGPU for anything. It's completely ignored because it's usually completely useless compared to your main discrete GPU. Modern iGPUs are a

> No one is using the iGPU for anything. It's completely ignored because it's usually completely useless compared to your main discrete GPU. Modern iGPUs are actually quite powerful is my understanding. I think the reason no one does this is that the software model isn’t actually there/standardized/able to work cross vendor since the iGPU and the discrete card are going to be different vendors typically. There’s also little motivation to do this because not everyone has an iGPU which dilutes the economy of scale of using it. It would be a neat idea to try to run lighter weight things on the iGPU to free up rendering time on the dGPU and make frame rates more consistent, but the incentives aren’t there.

softfalcon 3y ago
I agree the incentives aren't there. Also agree that it is possible to use the integrated GPU for light tasks, but only light tasks. In the high performance scenarios where there is all three (discrete GPU, integrated GPU, and CPU) and we try and use the integrated GPU alongside the CPU, it often causes thermal throttling on the shared die between iGPU and CPU. This slows the CPU down from executing well, keeping up with state changes, and sending needed data to the keep the discrete GPU utilized. In short, don't warm up the CPU, we want it to stay cool, if that means not doing iGPU stuff, don't do it. When we have multiple discrete GPU's available (render farm), this on-die thermal bottleneck goes away and there are many render pipelines that are made to handle hundreds, even thousands of simultaneous GPU's working on a shared problem set of diverse tasks, similar to trying to utilize both iGPU and dGPU on the same machine but bigger. Whether or not to use the iGPU is less about scheduling and more about thermal throttling.
- vlovich123 3y ago
  That’s probably a better point as to why it’s not invested in although most games are not CPU bound so thermal throttling wouldn’t apply then as much. I think it’s multiple factors combined. The render pipelines you refer to are all offline non-realtime rendering though for movies/animation/etc right? Somewhat different UX and problem space than realtime gaming.
zokier 3y ago
It still annoys me how badly AMD botched their Fusion/HSA concept, leading igpus to be completely ignored in most cases.

softfalcon 3y ago

I agree the incentives aren't there. Also agree that it is possible to use the integrated GPU for light tasks, but only light tasks. In the high performance scenarios where there is all three (discrete GPU, integrated GPU, and CPU) and we try and use the integrated GPU alongside the CPU, it often causes thermal throttling on the shared die between iGPU and CPU. This slows the CPU down from executing well, keeping up with state changes, and sending needed data to the keep the discrete GPU utilized. In short, don't warm up the CPU, we want it to stay cool, if that means not doing iGPU stuff, don't do it. When we have multiple discrete GPU's available (render farm), this on-die thermal bottleneck goes away and there are many render pipelines that are made to handle hundreds, even thousands of simultaneous GPU's working on a shared problem set of diverse tasks, similar to trying to utilize both iGPU and dGPU on the same machine but bigger. Whether or not to use the iGPU is less about scheduling and more about thermal throttling.

vlovich123 3y ago
That’s probably a better point as to why it’s not invested in although most games are not CPU bound so thermal throttling wouldn’t apply then as much. I think it’s multiple factors combined. The render pipelines you refer to are all offline non-realtime rendering though for movies/animation/etc right? Somewhat different UX and problem space than realtime gaming.

zokier 3y ago

It still annoys me how badly AMD botched their Fusion/HSA concept, leading igpus to be completely ignored in most cases.