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Old 27 July 2019, 16:47   #678
NorthWay
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Join Date: May 2013
Location: Grimstad / Norway
Posts: 609
Quote:
Originally Posted by roondar View Post
True, a chunky display can save up to 1/4th of the bandwidth for cookie cut bobs in the optimal case.
It should _always_ save 1/4th if you can use the (rather safe) assumption that a chunky pixel with all bits clear means select source instead of bob. If you want something ZX Spectrum like with a mask around the bob then you would need as much bandwidth.
The optimal case however depends and memory width, blitter width, the number of parallell blitter units, and if you can have dynamic memory access sizing. I.e. no "zero" pixels in the bob data you read can simply convert the cookie-cut into a copy plus pointer advance. (Note that this does not work if you want to blit from a backup buffer to the viewed buffer, then we are back to 1/4th.) Then depending on circumstances you can juggle bus sizing to maximize the number of conversions.
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