SetRGB4 bug on the A1200
I am curios, am only I so "lucky" that have to face this bug? The documentation about SetRGB4 claims that only 4 bits of d1-d3 registers are used. It is true for the A500 but it is not true for the A1200. I have to use
Code:
and.b #15,d1 I will be grateful for more clarifications about this issue. |
It's worse than you think.
For AGA graphics SetRGB4 converts the color values from 4 bit to 32 bit and then calls SetRGB32. However in KS3.0 (and 3.1, others?) the higher bits are not masked off, so some may 'leak' into the 32 bit value. The code in the ROM looks like this:- Code:
swap d1 To prevent this you must ensure that bits 31-28 and 7-5 are cleared when calling SetRGB4. So to be safe you should do eg. Code:
moveq #15,d4 |
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