[UAE] How much does the processor matter?

[runequester]

I haven't tested this much, but how much does UAE emulate the various processor speeds and how accurately?
 
In other words, how much of a difference does it make for emulation, between selecting a 68020 or 68040 f.x. other than some compatibility issues ?

[Trev]

Speed is relative to the host processor. If you let it, UAE will run as quickly as the host processor allows. You can throttle various aspects of the emulation by enforcing chipset timing or cycle exact emulation.

[runequester]

Speed is relative to the host processor. If you let it, UAE will run as quickly as the host processor allows. You can throttle various aspects of the emulation by enforcing chipset timing or cycle exact emulation.

Would it be possible to tweak it to match an actual 68030 f.x., or does UAE just match the instructions and whatnot for those processors ?
 
Sorry if these are dumb questions

[AmigaHeretic]

I haven't tested this much, but how much does UAE emulate the various processor speeds and how accurately?
 
In other words, how much of a difference does it make for emulation, between selecting a 68020 or 68040 f.x. other than some compatibility issues ?

It basically makes no difference if you select 020 or 040 as far as speed is concerned.  People usually suggest using the 020 setting as there is more software specifically optimized for 020/030 as opposed to 040.  

I happen to set everything up as 040 in my WinUAE environment years ago so I have just stuck with that, but speed wise it really is the same. i.e. you don't get "more" speed selecting 040.

[AmigaHeretic]

Would it be possible to tweak it to match an actual 68030 f.x., or does UAE just match the instructions and whatnot for those processors ?
 
Sorry if these are dumb questions

Yeah, it basically matches the instructions.  On any relatively modern computer with JIT selected, WinUAE BLOWS the 030 out the water.  There is no real 68k CPU that comes close to the JIT 68k in WinUAE.

[runequester]

Gotcha. Thanks guys.
 
I was less concerned with overall speed, and more interested in seeing how certain games would run with certain processors, but I guess that might not work well under emulation.
 
EDIT: Also, if a game or app had specific optimizations for a given processor (f.x. Battle Isle had a 68020 option when installing), would UAE benefit from selecting that ?

[ChaosLord]

You should always select 020+FPU as it is the most compatible and fastest out of 020-060

But very old, badly coded games will require you to select 000

Those are the only 2 choices you ever need to use.

[Karlos]

You should always select 020+FPU as it is the most compatible and fastest out of 020-060

But very old, badly coded games will require you to select 000

Those are the only 2 choices you ever need to use.

For games, yes. For serious use, I usually use 68040 since I've copied a lot of libraries etc from my real system. It's not any slower than 68020 for me.

[spirantho]

Just wanted to point out that the 68020+ has more instructions so will provide faster emulation than the 68000 emulation which has to do two (emulated) instructions where the 68020 may do just one. So yes, 68020 wherever you can, 68000 if you really need to.