480x960 requires 4 times the frame buffer memory of 320x480. Assuming a double-buffered frame buffer system, that's 2 or 4 megabytes (* depending on color depth) of memory, either hidden inside the A4, or taken away from apps. Possibly a lot more if all the CG graphics contexts inside every view object are also quad density (in terms of total pixel memory) for maximum resolution text rendering.
So apps may end up with less maximum available memory on the new device.
* With quad density, one option is to only use 6-bits of color per pixel, and dither in groups of 4 to emulate 8 bits-per-pixel color. At 300+ dpi, no human eye would notice the difference without magnification.
So apps may end up with less maximum available memory on the new device.
* With quad density, one option is to only use 6-bits of color per pixel, and dither in groups of 4 to emulate 8 bits-per-pixel color. At 300+ dpi, no human eye would notice the difference without magnification.