> >time it wants to do DMA (this is part of the reason why sprites turn off
> >automatically when the Kernal LOAD routine starts), which interferes with
> >the exact timing the IEC bus protocol demands. To get this speed boost
> >back, you send the drive a UI+ command, and then turn the 64's screen off
> >with POKE 53265,11.
>
> That is interesting. On the Atari 8-bit, turning off DMA turns off video.
> You get a 30% speed increase by doing this (poke 559,0). Drive access
> does not do this though it's tricky to do both video and heavy i/o at the
> same time. This was fodder for lots of demo's that did sound, disk, and
> video at the same time.
You get a CPU speed boost also by turning off the screen, but not more than
six or seven percent, people have calculated. VIC-II DMA ("badlines") normally
occur every eight scanlines, so if you know how many scanlines are on your
screen, you can make a rough calculation how much the DMA overhead is (there
are some other small factors affecting the value also, but that's the general
notion). Sprites worsen VIC-II's hit on the bus.
--
----------------------------- personal page: http://www.armory.com/~spectre/ --
Cameron Kaiser, Point Loma Nazarene University * ckaiser_at_stockholm.ptloma.edu
-- Whatever it is, I'm against it. -- Groucho Marx ----------------------------
Received on Sat Nov 18 2000 - 21:37:45 GMT