A few years ago I was interested in a way to improve bilinear filter specifically for the GBA core, I had no idea at the time how to do it, and if it had been done by the retroarch people it would have been on the CPU which would not help GBA games. None of this matters now because of Enhanced mGBA; it manages it on the GPU. However there are cases where this option is useful for example a game on the PC Engine can change from 352x240 to 256x240, retroarch is not capable of automatically changing these resolutions and instead forces you to use one at a time. Another case would be games that use a horizontal resolution higher than 320, because retroarch can't go higher than 640. Yet another case would be arcade games that use 240 lines and no overscan safe huds. Because of these reasons and for the sake of having options, I managed to duplicate an existing filter and break it so that it does nothing but keep the output image multiplied by 2. You can try it for yourself: https://www.dropbox.com/s/euuqz9m0hebewpo/RA_backup.zip?dl=1 Only cores fb_alpha, cps1/2, neogeo, genesis plus(titled gg.dol in the zip), gambatte, mgba, and pce_fast support it. You need the "normal2x.filt" found in the filters folder in the zip and simply select it from Settings/Video/Software filter/ I tested a couple of games, performance lost in GBA games is quite clear but the other less demanding cores should have little to no problem. My biggest motivation was a single game anyway.