Resolution scaling vs. RPCS3

[themanuel]

I'm curious to know if RPCS3 might do resolution scaling differently from Dolphin.  As described in their blog post, scaling RPCS3 to 4K level resolutions has negligible impact on performance.  On dolphin, scaling to higher resolutions, even though containable by my system, does cause a measurable degradation.

Is this due to an inherent different between the two rendering systems?

[JMC47]

The main reason Dolphin would get slower at higher resolution is due to costly GPU syncs with features like EFB2RAM + EFB Access to CPU. EFB Access to CPU is especially interesting as more pixels to read = much slower.

[themanuel]

Thanks for the info, as always.

[JMC47]

I actually brought this up on RPCS3's discord to get some more concise answers on their end. And the answer is pretty obvious.

Games that need GPU syncs behave the same on RPCS3 as they do on Dolphin, getting much slower at higher resolutions. Unlike Dolphin, the CPU bottleneck is more common than a GPU bottleneck, so raising the resolution is less likely to cause slowdown in most games.

[themanuel]

Interesting. Thanks for digging further. It sounds like you've found a reason for the difference in behavior.
I suspect Cemu is more like Dolphin in this regard, since using higher resolutions through the graphics packs is not exactly "free".