Microsoft has announced a brand new feature for Windows known as CASO which supports hybrid iGPU & dGPU switching on laptops across all three GPU vendors without the requirement of MUX.
Microsoft CASO Will Let Hybrid Laptops Switch Between iGPU & dGPU More Efficiently Without Requiring Proprietary Solutions
According to Microsoft, CASO or Cross Adapter Scan-Out is a solution devised for platforms that use a hybrid GPU configuration which includes both iGPU and dGPU. Laptops which include both iGPU and dGPU will use the iGPU to run the display and can also be used for light-weight tasks & the dGPU is responsible for the heavy lifting such as gaming and other rendering & creation tasks.
Modern-day laptops use proprietary solutions to fully utilize the hardware onboard and to switch between the iGPU and dGPU based on the workload. NVIDIA has Advanced Optimus while AMD's solution comes in the form of Smart Access Graphics. Both solutions use a MUX (Multiplexer) chip that switches between the iGPU and dGPU.
But both of these are proprietary solutions and there will be cases where certain vendors don't support such features. For example, AMD has used Smart Access Graphics on its premium products under the "AMD Advantage" program and NVIDIA also uses these features across its own ecosystem of laptops. So what if you don't have an NVIDIA Optimus or AMD Smart Access Graphics laptop?
That's where Microsoft's CASO comes in. Without a MUX switch, two copies of a rendered frame will be sent out. One from the dGPU to a shared resource and the other from the shared resource to the iGPU (handles display). This example includes gaming and while it works, it's not efficient and leads to lower FPS and higher latency. With a MUX switch and the same gaming workload, the laptop can switch the display connection to the dGPU too so that it doesn't pass through a shared resource with the iGPU. This maximizes performance by using the GPU that is best for the task the laptop is running.
With CASO, you aren't just getting rid of the shared resource but also getting rid of the MUX switch requirement. CASO requires just one copy of the rendered frame which is directly scanned out to the display, resulting in better performance, lower display latency, and better battery times. As per Microsoft themselves, CASO is supported across a wide range of hardware and supports both DX11 and DX12 titles. Internal tests have shown an average of 16% FPS increase, 27% latency reduction & 45% decrease in Windows TDR (Timeout Detection & Recovery Events) with CASO enabled.
- AMD
“As a testament to our long-standing partnership and commitment to technology innovation, together we made hybrid graphics better for gamers, delivering more frames per second and lower latency. CASO is available starting on AMD RyzenTM 6000 Series processors with RadeonTM graphics, the most advanced processor in its class for high-end gaming on ultrathin notebooks.”
- Intel
“Intel strives to improve gaming performance and CASO delivers such improvements with reduced frame latency and increased FPS with our integrated and dedicated GPU offerings”.
- Nvidia
“All currently supported NVIDIA GeForce GPUs support CASO starting with driver version r515_00.
The latest GeForce Game Ready Driver is available for download here.”
Microsoft's CASO requires at least an AMD Ryzen 6000 CPU and Intel Iris Xe Graphics with WDDM 3.0 or above. You can try CASO for yourself if you are running a modern-day laptop.
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