Quote:
Originally Posted by sandruzzo
with only 16 colors you'll have 8 pixel into 32 bit insted 4. Not bad. You can almost double the pixel written into chip and fast memory
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You won't save on writes to the chunky buffer, though. The 68000 will have to do sequences like this.
Because you are now using nibbles you will have to merge them together. On my first post I mentioned the compiled sequences to draw vertical lines... as well as doing that for say even lines, for odd lines you will have to merge with ors:
move.b (a0)+,d0
or d0,160(a1)
or d0,160(a1)
Which means you will need to still write double the amount. Admittedly the chunky buffer copy will be the same speed for 2x1 pixels to 2x2 pixels. Also, your texture data will need different versions for odd and even.
There is a way to cut the writes down in half which I mentioned in my first post and that is to process two vertical lines together and do the or on the cpu and write once for 2 pixels. Because to make this as fast as possible each possible vertical line will consist of a raw sequence of instructions. This gets complicated for 2 lines at once. For every possible line, we will need a version for odd and even lines together. That is a crap load of memory that the Amiga does not have.
But there's no harm in doing tests for this to rule what options are available. And if anybody wants to have a go at testing you are welcome.
I myself will be going down the 2x2 pixel route using 64 colours and 32 colours because my own testing proved that the bandwidth is comfortable spread over 3 frames. And if I want to go full screen PAL then I will have options to do that.
Who says I have not got a time machine... once this is proven I'm going back in time to change history
