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 PostPost subject: CPU-Z On A Virtual PC        Posted: Sat May 09, 2009 10:23 am 
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I was board, The VPC sees it as a single core CPU and the multiplier is at 20x it still has the power saving 400mhz then 2000mhz thing

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 PostPost subject: Re: CPU-Z On A Virtual PC        Posted: Sat May 09, 2009 10:29 am 
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You have to remember the CPU is emulated in most VPC situations.

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 PostPost subject: Re: CPU-Z On A Virtual PC        Posted: Sat May 09, 2009 10:53 am 
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I know, I was just interested to see what happens, I'll put CPUz on a floppy and try it on my WfW 3.11 486 sometime

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 PostPost subject: Re: CPU-Z On A Virtual PC        Posted: Sat May 09, 2009 10:59 am 
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mewrox99 wrote:
I know, I was just interested to see what happens, I'll put CPUz on a floppy and try it on my WfW 3.11 486 sometime


Are you sure CPUz will run on Win 3.1?


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 PostPost subject: Re: CPU-Z On A Virtual PC        Posted: Sat May 09, 2009 12:08 pm 
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I'm not to sure, If not then i'll just put the floppy version of 98 on that machine

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 PostPost subject: Re: CPU-Z On A Virtual PC        Posted: Sat May 09, 2009 12:28 pm 
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VirtualPC (or VMWare) does not emulate the CPU. A simple evidence for that is that if it were to emulate a CPU you would be able to choose which instruction set to emulate. Do you want to run a 386? or a Pentium Pro. Perhaps a Xeon?

It uses the host processors capabilities and forwards the instructions to the guest, with some exceptions since a lot of handles has to be emulated in the guest, and not all instructions can be virtualised without too much speed penalty.

A real CPU emulator is for example Bochs which can emulate an entire instruction set regardless of your host CPU (since you can run Bochs on a various of platforms). Bochs can for example emulate a true 386 CPU even if you got a Core2 system. I can emulate an Alpha instruction set (IA-32) quite well too. VirtualPC for Mac (PPC) worked in a similiar way, emulating the x86 instruction set and translated it so it can be run on the PowerPC instruction set.

The reason your host shows to be dualcore and the guest to be single core is most likely (not sure here tho) because the guest runs as a single CPU system. VMWare has actually the selection where you can choose how many cores you want to run in a single guest. As for the speed settings it's most likely a timing issue. The guest inside isn't 100% as fast as the host (naturally) which means the timing is off and it shows to be a slower CPU. But if you take notice it STILL says it's a Core2 Duo E6400, it reports the family, model, stepping etc the same for both host and guest, and all other info such as cache. As for CPU-Z's detection of cores it's most likely quite simple.

However if you check the supported instructions it differs a lot since VPC/Vmware can't handle all instructions. If you run the guest as a 32bit system then the "virtual CPU" will not report it can handle EM64T instructions. Same goes with SSE2-3 etc since it's not yet supported by VPC.

Again, if VPC was an emulator then you could make that CPU-Z report it was an Intel 286 running at 2GHz, since it would be a simple task then to alter the values of what the emulator reports to its guests.

Virtualising is a quite tricky feat since not only do you have to keep the guest completely isolated from the host system, but you have to do it with the least speed penalty. But since more or less all of it isn't emulated it's very fast. How fast would your "emulator" be if it had to emulate the full Core2 instruction set completely in software?

Video card, sound card, chipset etc however is fully emulated, which is also why it's so slow and emulates only a basic and now antique chipset and video card. If emulation was that simple then why not emulate the full instruction set of an Nvidia GTX295 right away? =D The next VMWare version is supposed to be able to use a dedicated GPU for running a full video card (much like virtualising it as well in full).

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