RE: [stella] Another kernel is rolling

Subject: RE: [stella] Another kernel is rolling
From: "Fred Quimby" <c9r@xxxxxxxxxxx>
Date: Thu, 7 Apr 2005 05:21:33 -0400
Strangely, my posts are not going through... So i'll try again.  Forgive me 
if this actually goes up twice.

I'm currently experimenting some dirty tricks in order to save space.  If 
the 9-byte VSYNC is giving trouble, you might be able to use this.  Under 
certain conditions (stack pointer = $FF, that is) you can do VSYNC in 8 
bytes, provided you combine it with the overscan timer.

    LDX INTIM ; overscan timer
    BNE .1
    ; x=0, Z flag = 0 here

    ; If stack pointer isn't initially $FF, this won't work!

    TXS     ; set stack pointer on top of VSYNC register ($00)
    PHP ; pushes Z=1 (bit 1 set) to VSYNC then resets SP to $FF.
    INC WSYNC ; INC does two writes to WSYNC, giving you two scanlines!
    STX VSYNC ; x=0, ends VSYNC

I haven't actually tried this on real hardware, so use at your own risk!

>From: "Aaron" <stella-receiver@xxxxxxxxxxxxxxxxx>
>Reply-To: stella@xxxxxxxxxxxxxxxxxx
>To: stella@xxxxxxxxxxxxxxxxxx
>Subject: RE: [stella] Another kernel is rolling
>Date: Thu, 7 Apr 2005 01:27:48 -0400
>Dennis Debro said:
> > I ran 2 versions on my 7800 via CC2, one with the old VSYNC routine and
> > another with Edwin's routine. The title screen synced fine with the old
> > VSYNC routine. When I used the one from Edwin, that's presently in the
> > macro.h file, the title screen didn't sync properly.
>Well, assuming that's actually the problem, I think it's sufficiently
>weird that I can't be mad about not finding it.
>Thanks Dennis!
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