Posted By
MMS
on 2011-05-07
06:00:28
 |  Re: Bitmap colors'reversed nibbles
off:
Well, Istvan you know the +4 much better than me, but let me add two comments:
1) c64 can use 3 different colors per char. +4 has two dma, and the cpu is faster. So... (ok i understand that luminance has to be read separately too, but thats why they not store all the comlete color1 at one place, the second color at a second place). The machine has to read the memory 4 times for two colors, while with the above only two times. So even 4 independent color theoretically possible in same bandwidth.
2) standardization in an arhitecture is a key for easy programming. When they made the black color to be handled differently, they generated a "special case", though they could add 7 more dark greys, and made shade of white more "whitish".
3) oh,that bloody flash bit... It caused so many limitation here and there,just to save 2kb Rom on inverz charset.
4) as i know, the 1541 shift register hw bug caused this operation done by sw, told to made data transfer ~4x slower on the same serial bus. Then a question:if it is right, why 1551 is only 5x faster,despite paralell interface? An other hidden bug maybe? 
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