Thread: Amiga Vs ST
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Old 11 September 2014, 19:40   #480
Cyprian
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Join Date: Jul 2014
Location: Warsaw/Poland
Posts: 32
Quote:
Originally Posted by mc6809e View Post
Bitplane rasters can be interleaved on the Amiga. Bitplane one's first raster is followed by bitplane two's raster is followed by bitplane three's first raster, etc.

This mean that when blitting to a standard 16 color display, you can treat the screen as a single 320x800 bitmap and blit once.

Not sure how many cycles it eats, but in some cases those cycles are free since the the blitter is capable of accessing memory every two CPU cycles while the CPU is only fast enough to access memory every four CPU cycles. This means that DMA cycles that would be wasted on other platforms (like the ST) can be used by the blitter on the Amiga.
ok, actually I know (thanks to you and Toni) how to calculate blitting cycles. In py post, I asked about how many blitter registers CPU have to write in order to initialize such a blitter copy. I'd just like to calculate how many CPU cycles that initialization takes and where is worth to use CPU and where blitter.

Quote:
Originally Posted by mc6809e View Post
Depends on the code.
what kind of code do you mean?

I know that blitplanes have an impact onto CPU. If my calculations are correct in mode 320x256 mode, in case of 5bitplanes, ST is faster by 24% and in case of 6bitplanes 37%. In case of 320x200 mode 21% and 31% respectively.
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