Why exactly is this important? If it works and it works well, what's a number going to do?
3 meg. W x H x bits per pixel / 8. Keep in mind this is just one frame buffer. Most apps will use double or triple buffering (multiple copies of the frame buffer) to render into and then switch on a vsync to avoid tearing artifacts. As far as textures etc, that is up to each individual app.
screensaver400 said:Wirelessly posted (Mozilla/5.0 (iPhone; CPU iPhone OS 5_0_1 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Version/5.1 Mobile/9A405 Safari/7534.48.3)
Yeah, except it's four times the pixels.