Hyperspeed wrote:
What is meant by 'Chunky Pixel' anyway, I read it was a 1:1 pixel but then NTSC 640x480 is 1:1 (with overscan)?
Assuming a 256-colour display, chunky screenmodes are those where one pixel on the screen can be written in a single go using one byte of data.
In contrast, the Amiga's AGA display in a 256-colour mode would require 8 separate writes of one bit each, to each of the eight bitplanes that make up the final display.
Taking a simple monochrome screen, one byte would equate to a horizontal line of 8 pixels, where the pattern of the line equates to the binary pattern of the value written to it (where 1s correspond to a dot, and 0s to a blank). E.g. a solid line would require a value of 255 (FF hex) to be written as this equates to 11111111 in binary, and a blank line would require 0 to be written as this equates to 00000000 in binary, with a stippled effect being obtained by writing alternate 0s and 1s as in 01010101 (byte value of 85 (55 hex)). The Amiga's native screenmodes are effectively made up of multiple monochrome-style "planes" of graphics, which are then layered together by the chipset.
The Akiko chip simplified the writing to all of these bitplanes and effectively gave the developer a chunky display to work with, where one byte written to change a single pixel would be split across the eight bitplanes via hardware, thereby speeding up screen updates vs doing the same operation in software.
I'm sure someone can explain that better than I've just attempted!
- Ali
