Darren New <dne### [at] sanrrcom> wrote:
> > (Besides those being nice "round" numbers, otherwise that ordering makes
> > absolutely no sense, 

> The only reason I could think of would be memory bandwidth issues. DMA was 
> quite expensive at the time.

  There might have been some technical reason for that odd pixel ordering,
but I have the gut feeling that they decided on that ordering for some
subjective (and ultimately stupid) reasons, like "it looks cool when an
image being loaded appears in sparse scanlines which get slowly filled"
or something along those lines.

  It might perhaps had even made some sense if the 8-pixel jumps from one
pixel row to the next would have been continuous from top to bottom, but
instead, as said, the screen was divided into three parts so that the upper
third of the screen would fill up first, and when it was completely full,
then the middle third, and then the lower third.

  (With a vertical resolution of 192 pixels one third makes a round amount
of 64 pixels, ie. 8 rows of 8x8 blocks. While all that sounds all round and
nice in binary, it's a real pain in the ass to draw anything, and you have
to waste precious clock cycles into jumping properly around inside the
screen buffer to draw something. In the Spectrum everything had to be done
with the CPU, as there were no auxiliary graphic chips of any kind.)

-- 
                                                          - Warp

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