jtchip wrote on 2025-12-21, 01:39:

Not necessarily, the earlier ones used a mux to switch the display outputs between the integrated and discrete GPUs. AIUI those […]
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myne wrote on 2025-12-20, 12:03:

All laptops since gpus were ever added do this.

Not necessarily, the earlier ones used a mux to switch the display outputs between the integrated and discrete GPUs. AIUI those made in the last 10-15 years, perhaps when PCIe bandwidth became sufficient so as to not cause a significant performance dip, switched to mux-less designs.

myne wrote on 2025-12-20, 12:03:

All it really is is copying the framebuffer from one card to another.

Indeed but it needs the drivers to have ability to do that. Easier to do that on a laptop with a fixed configuration and laptop vendor-supplied drivers but a potential nightmare on a desktop with any combination of devices and drivers.

In a sense this is a special case of ATI Crossfire where instead of sharing the rendering between 2 GPUs (one of which can even be integrated in the case of Hybrid Crossfire), one GPU does all of the rendering work.

afshin6760 wrote on 2025-12-20, 19:03:

After a little research, I found out that using this method with an iGPU is much more risky because many motherboards do not allow the simultaneous use of an iGPU and graphics.

It depends on the motherboard. Don't know about Windows but on Linux this combination has some use because the dGPU is disabled, and hence draws no power, when not in use and iGPUs have lower power draw at idle or light loads.

In any case, this thread really belongs on Milliways since an old secondary GPU that can do this really isn't that old. You should ask on other forums too.

Thanks, I’ve asked this on Milliways forum as well.

Don't dupe threads. You already have one for your issue.