Personnaly, the highest I've tried is 640x480, but I don't think 800x600 is supported... Anyway best way to know it is actually to try it !
Else, if you really need it, you can still render your stuff to a 800x600 framebuffer and stretch it to the display (so 640x480). Then, as aspect ratio is the same and using some bilinear filtering, it should looks good !
800x600 resolution
Actually, the PS2 fully supports SVGA resolutions up to 1280x1024 as well as HDTV resolutions. It's just that most people don't have the monitor cable and monitor for SVGA modes, or the component cable and HDTV for HDTV modes. If you check the PS2linux site, there are people using all three: normal TV (PAL or NTSC), SVGA, or HDTV. There are folks who even use 1920x1080i HDTV - although given the limitation of memory in the GS, you only get 16bit color and no double-buffering at that resolution.
Generally, 640x480 is as high as you can go for millions of colors (24/32 bit mode) and still have double-buffering, a Z buffer, and still have room for textures. If you switch to thousands of colors (15/16 bit mode), then you can go much higher on resolutions.
Generally, 640x480 is as high as you can go for millions of colors (24/32 bit mode) and still have double-buffering, a Z buffer, and still have room for textures. If you switch to thousands of colors (15/16 bit mode), then you can go much higher on resolutions.