spaztron64 suggested that the GRCG might not always write all 4 planes
if one of the tile registers is 0. By changing the color and comparing
the results of this benchmark, we can prove that real hardware has no
such optimization.
Completes P0233, funded by [Anonymous].
Running this on various PC-98 models confirms that unchecked blitting
(i.e., what you would intuitively consider to be the best method) is in
fact faster than checking either byte of a 16-pixel-wide sprite
beforehand, and has been throughout the PC-98's lifespan. For optimal
performance on the 286 and 386, we might want to use MOVS instead of
MOV, but even that difference is way too small to truly matter.
Also, nice to see turns out that our blitter outperforms a naive pure C
implementation by 2-4×, depending on the model. And master.lib is not
*that* much faster…
The gaiji in `Research/blitperf.bmp` were taken from the Unifont
version 15.0.01 glyphs for:
• U+2022 BULLET •
• U+23F1 STOPWATCH ⏱
• U+1F40C SNAIL 🐌
Part of P0233, funded by [Anonymous].
nmlgc