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In high performance scenarios, the GPU is running full blast while the CPU is running at full blast just feeding data and pre-process work to the GPU. The GPU

In high performance scenarios, the GPU is running full blast while the CPU is running at full blast just feeding data and pre-process work to the GPU. The GPU is the steam engine hurtling forward, the CPU is just the person shoveling coal into the furnace. Using the integrated GPU heats up the main die where the CPU is because they live together on the same chip. The die heats up, CPU thermal throttles, CPU stops efficiently feeding data to the GPU at max speed, GPU slows down from under utilization. In high performance scenarios, the integrated GPU is often a waste of thermal budget.

MaxBarraclough 3y ago
Doesn't this assume inadequate cooling? A quick google indicates AMD's X3D CPUs begin throttling around 89°C, and that it's not overly challenging to keep them below 80 even under intense CPU load, although that's presumably without any activity on the integrated GPU. Assuming cooling really is inadequate for running both the CPU cores and the integrated GPU: for GPU-friendly workloads (i.e. no GPU-unfriendly preprocessing operations for the CPU) it would surely make more sense to use the integrated GPU rather than spend the thermal budget having the CPU cores do that work.
- softfalcon 3y ago
  What the specs say they'll do and what they actually do are often very different realities in my experience. I've seen thermal throttling happening at 60°C because overall, the chip is cool, but one core is maxing or two cores are maxing. Which is common in game dev with your primary thread feeding a GPU with command buffer queues and another scheduling the main game loop. Even when water cooled or the high end air cooling on my server blades, I see that long term, the system just hits a trade-off point of ~60-70°C and ~85% max CPU clock even when the cooling system is industry grade, loud as hell, and has an HVAC unit backing it. Probably part of why scale out is so popular to distribute load. When I give real work to any iGPU's on these systems, I see the temps bump 5-10°C and clocks on the CPU cores drop a bit. Could be drivers, could be temp curves, I would think these fancy cooling systems I'm running are performing well though. shrug

MaxBarraclough 3y ago

Doesn't this assume inadequate cooling? A quick google indicates AMD's X3D CPUs begin throttling around 89°C, and that it's not overly challenging to keep them below 80 even under intense CPU load, although that's presumably without any activity on the integrated GPU. Assuming cooling really is inadequate for running both the CPU cores and the integrated GPU: for GPU-friendly workloads (i.e. no GPU-unfriendly preprocessing operations for the CPU) it would surely make more sense to use the integrated GPU rather than spend the thermal budget having the CPU cores do that work.

softfalcon 3y ago
What the specs say they'll do and what they actually do are often very different realities in my experience. I've seen thermal throttling happening at 60°C because overall, the chip is cool, but one core is maxing or two cores are maxing. Which is common in game dev with your primary thread feeding a GPU with command buffer queues and another scheduling the main game loop. Even when water cooled or the high end air cooling on my server blades, I see that long term, the system just hits a trade-off point of ~60-70°C and ~85% max CPU clock even when the cooling system is industry grade, loud as hell, and has an HVAC unit backing it. Probably part of why scale out is so popular to distribute load. When I give real work to any iGPU's on these systems, I see the temps bump 5-10°C and clocks on the CPU cores drop a bit. Could be drivers, could be temp curves, I would think these fancy cooling systems I'm running are performing well though. shrug