Shaders on 1440p screen

Hi, I recently purchased a Galaxy S6 Edge and it has a 1440p screen. I’m having problems with the Gameboy shader. It worked fine on my older Galaxy S3 and also works on my 2013 Nexus 7. On the S6 the shader looks just like a bilinear filtered green palette. If I raise the scaling for each pass, the Gameboy effect starts to work, but the games will run way too slow. Is there a way to decrease the size of the screen, apply the shader and then upscale the screen. To me, it seems like the dpi is too high for the GPU to handle.

Hmm. Not that I know of. I have a 4K monitor and the effect looks like it’s supposed to without scaling the passes, but even my desktop GPU can’t get fullspeed at full res.