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Old 24 February 2015, 15:04   #17
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Originally Posted by kovacm View Post

I read from time to time (or to much time ) two type of arguments:

1) Atari ST has 10% faster CPU so 3D polygone games are faster
2) 3D games are ports from ST to Amiga so they do not use blitter otherwise they would be much faster on Amiga

I personally find "10% faster" argument irrelevant (unnoticeably).
but I am curios if there is any game on Amiga game that use blitter for 3D polygon fill?

or, even better: does somebody, with knowledge, can make explanation how much theoretical gain could be in game (not in demos!) using blitter for poly-fill?
Game or demo no difference - code is code - (assumed skilled developer use blitter).

HW data says on 1 plane up to 1 million pixels can be draw on screen - line mode (and up to 16 million pixel fillrate), count four planes (16 colors) so divide those figures by 4 and to be realistic by another 4 (25% efficiency, setup need time, short length vector may be more efficient draw by CPU).
Probably some work can be made on hybrid mode - CPU + Blitter + Copper and this can provide some gain.

Originally Posted by kovacm View Post
I have no knowledge about blitter: e.g. how much time would you spent on setting it up for fill vs filling with CPU alone? How much time is left for CPU while blitter doing fills (in case that there is no fast ram, and case with fast ram)...
Amiga 1200 case: if there is FastRAM, CPU could calculate 3D vertices while blitter filling polygons so filling could be almost "free"? Can copper somehow help with setting up blitter...?
Good question - Blitter use 20 registers so in worse case scenario setup may require to set them all so 20 R/W cycles (but it should be less than that).

Originally Posted by kovacm View Post
btw all 512KB expansion for Amiga 500 back in 80s and 90s were chipram? right? FastRAM was not common expansion in Amiga world until Amiga 1200?
Most of them - easy to connect and cheap, required by lot of software.
On some motherboards boards it can be mapped as CHIP RAM on some mobos not (with all OCS Agnus and presumably ICS Agnus this will be non CHIP RAM with speed limited by HW side aka SLOW RAM).
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