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Forums > C64 Coding > $39FF instead of $3FFF as alternative bit-pattern for open border

2016-10-11 12:28

YPS

Registered: Oct 2012
Posts: 5

$39FF instead of $3FFF as alternative bit-pattern for open border

I thought it's ALWAYS the last byte of the VIC-bank, that is displayed in the open border area (upper and lower).
But with "Extended Backgroundcolor Mode" on, the value of $39FF (of the VIC-Bank) is shown instead.
A usecase might be, that you can use all spritepointer together with the highest videoram - with "Extended Backgroundcolor Mode" off, the pointer of sprite 7 would be displayed as garbage in the border. Of course, there are solutions to avoid this, but maybe someone else find this usefull.

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2016-11-05 18:49

Graham
Account closed

Registered: Dec 2002
Posts: 990

ECM mode pulls two bits to 0. This is why $3FFF is pulled to $39FF.

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