Re: Marko's IRQ loader routine

From: Ojala Pasi 'Albert' (
Date: 1998-12-28 21:00:19

> one thing: my IRQ routine also changes $dd00. I've patched my IRQ routine so
> loader still causes the screen to flicker -- it seems like it assumes $dd00

You can't actually make the loader "$dd00-free", because it can be
interrupted between lda $dd00 and sta $dd00 anyway. If you need to
change $dd00 to display something, you need to stay in the interrupt
until $dd00 doesn't matter anymore.

You could make a hack in the interrupt routine to check where the
loader was interrupted (read the return address from the stack) and
fix the A register value (in the stack), but that would take in the
order of hundreds of cycles (100-200?) for each interrupt.

"Your Ambassador Delenn has a wonderful phrase: 'Faith *manages*.'"
	-- Brother Theo to Sheridan in Babylon 5:"Passing Through Gethsemane"
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