Gareth's Downstairs Computer
 wrote:
> Presumably there is a video buffer somewhere which
> will display any pixels that you choose to put there,
> without there being any activity from the GPU part of the
> video controller?

It depends. Some screens (like 3.5" or 2.8" TFT screens from AdaFruit) have
software video buffer located in RPi memory that you have to use directly,
bypassing the GPU. It's because these screens are connected right to RPi
GPIO pins. They, of course, would lack any hardware acceleration.

> How is its area, frame rate and X and Y pixel range determined?

It determined by screen driver which is usually supplied by the screen
manufacturer. Software for such screens usually written for pre-determined
screen size, i.e. programmer write in the code something like "var
ScreenSize.x = 320; var ScreenSize.y = 240;"

> Also, for dynamic video such as DVB there must be some means of
> instructing the graphics processor how to overwrite that area?
>
> Has there been published any disassembly of the graphics library
> to work out what is going on so that 64 bitters could drive it
> from A64?
>
> Yours etc,
> Confused from Tunbridge Wells
>
>
>

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