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Weird Zen 3 Behavior

Posted: Sat 15 Jan, 2022 8:10 am
by CryptidWorks
So, I'm running a 5600X over here and I can emulate up to a Pentium 200 with a Voodoo 3 3000 flawlessly.

However, when I try to step up to a Pentium 233 I'm noticing PCEM is actually leaving a lot of power on the table. My CPU can sustain a clock speed of 4.5Ghz all core when it's turbo kicks in but I'm getting drops in emulation speed with my CPU barely hitting 3.5GHz and 80% usage at that speed on the core it's using for CPU emulation. It seems almost like the software is afraid to hit the host CPU to hard so it's just stopping when it reaches a certain load on the core.

Re: Weird Zen 3 Behavior

Posted: Sat 15 Jan, 2022 12:24 pm
by unreal9010
In theory, your CPU should do at least Pentium II 233 if not 266 flawlessly considering that the upper limit of flawless operation on my i7 6700 non-K is Pentium MMX 166. I can play several games at 100% on Pentium II 233 and some 3D-accelerated ones (e.g. The Need for Speed III) work most of the time at 100% even on Pentium II 333.
Try various core affinity settings in Windows task manager and see if it makes any difference.

Re: Weird Zen 3 Behavior

Posted: Sat 15 Jan, 2022 2:23 pm
by unreal9010
Also, try setting SMT and PBO either on or off, depending on what your current setings are.

Re: Weird Zen 3 Behavior

Posted: Sat 15 Jan, 2022 9:52 pm
by CryptidWorks
unreal9010 wrote: Sat 15 Jan, 2022 12:24 pm In theory, your CPU should do at least Pentium II 233 if not 266 flawlessly considering that the upper limit of flawless operation on my i7 6700 non-K is Pentium MMX 166. I can play several games at 100% on Pentium II 233 and some 3D-accelerated ones (e.g. The Need for Speed III) work most of the time at 100% even on Pentium II 333.
Try various core affinity settings in Windows task manager and see if it makes any difference.
I'll have to try setting the software to high priority and playing with core affinity on it to see if that works. PBO and SMT shouldn't affect anything since all other CPU heavy software like RPCS3 can spin up the cores to max load and clockspeed fine.

Edit: playing with that stuff to give it high priority and limit it to just the top six threads improved it somewhat so it can hit 100% load and spin up the core being used for CPU to 4.6Ghz now but heavily CPU bound games like Quicktime stuff still can't quite maintain 100% emulation speed on a 233.

Edit 2: I seem to have gotten a Pentium 233 working by effectively disabling SMT for PCEM by setting core affinity to only the even threads, that is really strange and something I've seen in an emulator before. I have now jerry-rigged a CMD shortcut that boots the software with affinity on those cores so it runs without SMT.

Re: Weird Zen 3 Behavior

Posted: Sat 15 Jan, 2022 10:41 pm
by unreal9010
Journeyman Project 3 may be good for benchmarking as it is heavily Quciktime dependent.

Re: Weird Zen 3 Behavior

Posted: Sat 15 Jan, 2022 10:49 pm
by CryptidWorks
unreal9010 wrote: Sat 15 Jan, 2022 10:41 pm Journeyman Project 3 may be good for benchmarking as it is heavily Quciktime dependent.
I've been using The Mummy: Return of the Pharaoh. The game uses quicktime video files for literally everything, so it hammers the virtual CPU hard.

Re: Weird Zen 3 Behavior

Posted: Sun 16 Jan, 2022 1:05 am
by CryptidWorks
I'd like to post a final update that using that "hack" of forcing PCEM to run without SMT I now have a Pentium II 233Mhz with a Voodoo 3 3000 running at 100% speed on an R5-5600X. I think I've discovered something beneficial here.