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Old 25 April 2014, 13:50   #2
Toni Wilen
WinUAE developer
Join Date: Aug 2001
Location: Hämeenlinna/Finland
Age: 42
Posts: 19,560
Originally Posted by Mclane View Post

I've always wondered why there are those two options, wait for blitter and immediate blitter. I've read the mouse overs and understand what they do but what makes Winuae not be able to emulate the real hardware that you need to add hacks?

Is there no way to have a CPU secure speed so as not to need these, obviously I guess not otherwise you would have done it but I'm just interested as WinUAE handles so much of the hardware brilliantly.
Reason is 68(EC)020 CPU and blitter. CPU exact cycle-usage is only approximately documented and it is really complex due to longer pipelines and caches compared to really basic 68000. 68000 timing only depends on clock rate and memory access speed, 68020 speed depends on clock rate, cache state, previous instruction and memory access speed, 68020 can execute memory accesses and ALU operations simultaneously (for example previous instruction's write to memory can be active while next instruction starts executing)

Blitter is another problem, there are programs that poke blitter registers while blitter is already running, these can cause really weird side-effects or nothing at all depending on blitter's (unknown) internal state. (EDIT: This is practically the last remaining A500 compatibility problem)

(I wrote longer answer in some other thread I can't seem to find anymore)

Also they are not just for compatibility, they also allow to run fast cpu modes to run even faster and most programs with missing blitter waits work with fast CPU modes if wait for blitter or immediate blitter is enabled.

The other question is that when I'm running the latest set of beta's in full screen I get a long white line a couple of pixels high the same length as the viewable screen but about 10 pixels below it in the black border that goes when the machine boots with no disc in..

Just running it as a totally untouched config from the quicklaunch screen.
"Works for me". (Hint: no information whatsoever included, not even KS version. Config and log is _always_ needed, at least screenshot is minimum here.)
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