According to Hatari code:
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* Write to video shifter palette registers (0xff8240-0xff825e)
*
* When writing only to the upper byte of the color reg
* (instead of writing 16 bits at once with .W/.L).
* In that case, the byte written to address x is automatically written
* to address x+1 too (but we shouldn't copy x in x+1 after masking x ;
* we apply the mask at the end)
* Similarly, when writing a byte to address x+1, it's also written
* to address x
* So : move.w #0,$ff8240 -> color 0 is now $000
* move.b #7,$ff8240 -> color 0 is now $707 !
* move.b #$55,$ff8241 -> color 0 is now $555 !
* move.b #$71,$ff8240 -> color 0 is now $171
* (bytes are first copied, then masked)
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If somebody could do similar test also on Falcon, that
would be appreciated too. Current Videl emulation code
has that functionality commented out, with a TODO...