Problem with cycle-exact and custum CPU emulation speed

[pintcat]

Hi,

I tried to run WinUAE 2.1.0 with cycle-exact mode and a custom CPU frequency of 50MHz and ended up with a black screen (which means it didn't even boot whatever I tried to load). I retried it with several setting and also with the A1200 quickstart preset, but got always the same result.
The older 2.0.1 still works with these settings.

[NewDeli]

What are you trying to boot the emulated A1200 with ? An ADF, a preconfigured WB ?

[pintcat]

I tried to boot a Workbench 3.1 from HD as well as some games from floppy, but the drives didn't even start to run. After some further testing I found out that the CPU frequency doesn't matter. I just have to set the custom option and WinUAE refuses to boot at ANY speed.
Btw. host OS is WinXP SP3

[Toni Wilen]

I can't duplicate. A1200 quickstart most compatible + CPU freq set to custom (default or whatever) = boot screen appears and at least WB disk boots.

[pintcat]

This problem is becoming odd. I retried the the most compatible quickstart setting with only changing CPU frequency to Custom (as you did) and it worked. But this setting uses the 68020 CPU which I rarely use. So I tested the other types and the problem appeared with the 030, 040 & 060 in most cases. After adding some FastRAM these CPU types never worked.
Hope someone can confirm this behavior, it's quire annoying to be the only douchebag with this problem

[UncleSpam]

Agreed...

Just tested it in Cycle-exact mode and no Amiga HDD activity, just a boot screen, with the CPU pegged at 100% and 60Hz (NTSC mode).

I can supply log files, if needed.

Edit: It seems to get a bit farther in PAL mode, but still no HDD activity.

-Bogdan

[NewDeli]

Stick with 020 A1200 ? (not a solution by any mean, but it could make some sense since cycle exact approximations Toni has been working on lately mostly concern both 68000 & 68020 AFAIK)

[Toni Wilen]

Nobody said anything about non-68020 until it was too late...

Only 68000 and 68020 have real cycle-exact support (68020 accuracy is much worse than 68000).

Other CPU + cycle exact = chip ram accesses are slowed down by Agnus DMA, nothing else. Freezing is a bug (I guess) but also CE + non-CE CPU is unsupported configuration.

[pintcat]

Interesting news, this explains anything. If I got you right I should avoid using the cycle-exact option in conjunction with any other than the 68000 and the 68020 CPU - even if it wouldn't freeze - because it doesn't bring much advantage regarding the compatibility, right? Well, as long as there is no 68040 or 68060 required I can just emulate an 020@50MHz or more which should do the job Thanx for the enlightenment.

[Toni Wilen]

Correct. 68030 "CE" option will be implemented someday, when/if I find some way to emulate data cache without too much complexity. (and of course it still will be too fast in internal instruction processing but thats the problem when emulating CPUs with caches and pipelines..)

i've seen the same thing, and have a kind of workaround.

It is probably completely unsupported, and mostly untested (not all combinations of CPU and options) but it works for me as of Beta 25/RC3.


Turn Cycle Exact off.
Select 3.1 as the ROM.
Select a CPU
Choose 'Adjustable between CPU and Chipset'
Then drag the slider all the way to chipset side.

Do not turn on JIT.

Start it up, then you can adjust the CPU--Chipset until the speed 'feels' right.

[pintcat]

There's still one thing that confuses me... I tried to emulate an A1200 with CE, 68020 and the fastest CPU frequency preset (which is 2x at about 28MHz) and it ran great and as fast as it probably would with a real 28MHz CPU. Next I wanted to give it a bit more power by changing the option to custom and setting the speed to 50MHz which caused a terribly slow emulation. Than I lowered the value step by step, but nothing changed - even when I rerached 28MHz (and below). Apparently the custom option always slows down the emulation no matter what CPU frequency is used. But why?

Edit: One more thing to mention... The emulation only slows down if the CPU is heavily used as in some very good looking demos.

[Toni Wilen]

Originally Posted by pintcat

There's still one thing that confuses me... I tried to emulate an A1200 with CE, 68020 and the fastest CPU frequency preset (which is 2x at about 28MHz) and it ran great and as fast as it probably would with a real 28MHz CPU. Next I wanted to give it a bit more power by changing the option to custom and setting the speed to 50MHz which caused a terribly slow emulation. Than I lowered the value step by step, but nothing changed - even when I rerached 28MHz (and below). Apparently the custom option always slows down the emulation no matter what CPU frequency is used. But why?

Perhaps it only works before emulation is started or something, I don't really care about this too much

EDIT: 2x/4x and custom value work very differently. Multipliers = syncronous mode = CPU clock is locked to bus (DMA) clock and only power of 2 dividers or multipliers are allowed. Custom value = asyncronous, this is probably not working as expected

Edit: One more thing to mention... The emulation only slows down if the CPU is heavily used as in some very good looking demos.

Buy a faster PC. (seriously, check CPU%, I am sure it is going over 100%)

[pintcat]

Buy a faster PC.

I won't. My Intel Core 2 Quad with 4x 2.3GHz should be enough.

seriously, check CPU%, I am sure it is going over 100%

True. But as I said before, this only happens if the custom option is enabled and even if the speed is set to exactly the same value which is used by the preset options.

2x/4x and custom value work very differently. Multipliers = syncronous mode = CPU clock is locked to bus (DMA) clock and only power of 2 dividers or multipliers are allowed. Custom value = asyncronous, this is probably not working as expected

AHA! This brings light into my darkness! Now that I know this the custom option becomes quite useless to me because it turns my indeed fast machine into into a grumpy-geezer-acting jalopy in many cases.
Any chance to add a faster preset option in future versions which allows 4x/8x CPU frequency (about 56MHz)?

[Toni Wilen]

Originally Posted by pintcat

I won't. My Intel Core 2 Quad with 4x 2.3GHz should be enough.

There is never enough CPU power. (i7 920 at 4GHz here and it isn't enough)

CPU adjustment does work correctly except there is some extra multiplier (probably some testing stuff..) which makes all custom frequencies 8 times larger than asked.

Faster emulated CPU = more host CPU power needed. You will easily need more CPU power than is available if you increase clock rate too much. Check CPU%, it should always stay below 100%.