Question: CPU Emulation Speed (?)

[Arcade]

Hi guys,

Have a good weekend ...

Pls, I would like clear up doubt. In the option "CPU Emulation Speed -> Fastest possible", if I enable this option, the system loads very fast and runs very flow. But, at the bottom of the emulator window, it shows the "CPU 100% & the "FPS 49.8". I wonder if this means that my PC is using 100% of the CPU or it refers to the CPU of the emulated system, the A1200. One of my concerns is that may be using 100% of my PC CPU (Windows 10). Pls see the picture:

https://i.imgur.com/aSCYyF8.jpg

However, if I change the option "CPU Emulation Speed -> Approximate A500/A1200 or cycle-exact", the CPU was so variable: it went from 0% to 20%, 24% etc. in an instant (playing). Pls see the picture:

https://i.imgur.com/kos1TIV.jpg

Pls, I would like to know if the "CPU at 100%" only refers to the CPU of the emulated system and not to my PC in general.

Many thanks in advance.

[Toni Wilen]

It means it uses as much as host CPU power as available (=the faster the PC, the faster the emulation). But note that main emulation code can only use single CPU core.

[Arcade]

Thank you ever so much, Toni Wilen.

It is not clear to me... what are you referring to "host CPU" ? refers to the CPU of the emulated system and not to my PC ?

[rutra80]

Host CPU is the processor in your PC - Intel or AMD.

[Arcade]

Originally Posted by rutra80

Host CPU is the processor in your PC - Intel or AMD.

I don't fully understand it, rutra80.

The Task Manager in Windows 10, the CPU is showing 16% and in the emulator is showing 100%. I don't understand

[Rotareneg]

Windows task manager shows total CPU usage of all cores, so on a multicore CPU it won't show 100% unless all cores are busy.

[Arcade]

Originally Posted by Rotareneg

Windows task manager shows total CPU usage of all cores, so on a multicore CPU it won't show 100% unless all cores are busy.

So, the 100% is showing by the emulator refers to the CPU of the emulated system itself, the A1200. I understand that the option "CPU Emulation Speed -> Fastest possible" is overclocking. Is that right ?

https://i.imgur.com/aSCYyF8.jpg

[meynaf]

Originally Posted by Arcade

So, the 100% is showing by the emulator refers to the CPU of the emulated system itself, the A1200. I understand that the option "CPU Emulation Speed -> Fastest possible" is overclocking. Is that right ?

https://i.imgur.com/aSCYyF8.jpg

The 100% refers to the usage of the single core that's used to run the emulation. It is not about the emulated cpu.

[rutra80]

As already said WinUAE uses 1 core of your Intel/AMD CPU. WinUAE shows usage of that one core. When emulating real speed A1200, that Intel/AMD core is powerful enough to have some idle time so it doesn't show 100%. When emulation is Fastest possible, it uses 100% speed of your Intel/AMD core, so Amiga speed is as fast as possible on your Intel/AMD CPU.

So for example, on some weak Celeron CPU it will take ~25% of one of its cores to emulate 100% fast A1200.
When you tick Fastest possible it will use 100% of Celeron core and emulated A1200 will be ~400% fast.

On some powerful Ryzen CPU it will take ~10% of one of its cores to emulate 100% fast A1200.
When you tick Fastest possible it will use 100% of Ryzen core and emulated A1200 will be ~1000% fast.

[grond]

Originally Posted by Arcade

I don't fully understand it, rutra80.

The Task Manager in Windows 10, the CPU is showing 16% and in the emulator is showing 100%. I don't understand

Your computer obviously has six CPU cores which is why one 100% of one CPU shows as 16% in the Windows Task Manager. As said multiple times, the CPU usage indicator in WinUAE shows the load of one PC CPU core, not of the emulated CPU.

[Arcade]

I fully understood!

I really appreciate it. Thanks once again meynaf, rutra80 and grond.

[TroyWilkins]

Originally Posted by Arcade

I don't fully understand it, rutra80.

The Task Manager in Windows 10, the CPU is showing 16% and in the emulator is showing 100%. I don't understand

By default, the Task Manager in Windows 10 shows all CPU core loads as combined - so if you have a 4-core/4 thread CPU for example, and one core is at 100% utilisation while the others are hardly being used, it may show 26%. If this is the case, right click on the CPU graph and choose "Change Graph to" "Logical processors". This way, instead of showing all CPU logical processors as a single graph or value, it will show them all as separate, and when you use Fastest possible for WinUAE, it'll show one graph being maxxed out, while the others may hardly show any use.

Please see the attached pictures if this isn't clear enough, taken from the laptop I'm using to type this reply. It has an AMD Ryzen 3500u CPU, with 8 logical processors.