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is it possbile to develop emulation-virtualization hybrid?

Posted: Thu 22 Sep, 2022 5:06 am
by handlingcfg
hi, i wonder if is technically possible to write system that uses partially virtualization and switchable to emulation on demand for pcem
maybe basic operating system layer that could do this,let me explain it

we install control layer on pcem, we install guest os inside control layer, like vm inside vm,

when we want high speeds control layer sends instructions directly to the hardware via virtualization,
when we want to control speed for cpu, control layer spams hardware with useless codes with specific ratio to decrease performance to the level we want,
also if there is a instruction support issuses, maybe control layer could sends basic instructions directly to hardware and emulates other lacking instructions like MMX or 3Dnow.

Re: is it possbile to develop emulation-virtualization hybrid?

Posted: Fri 23 Sep, 2022 4:53 pm
by Benedikt
Spamming the CPU with useless instructions sounds like a profoundly silly idea if you ask me.
The proper way to slow down a virtual machine is to simply give it less CPU time.
VirtualBox, for instance, allows you to limit CPU utilization by a VM to a certain percentage, which can be very helpful for CPU-hogging games from the 90s.
Emulating unsupported instructions merely requires a trap handler.

Re: is it possbile to develop emulation-virtualization hybrid?

Posted: Sun 25 Sep, 2022 1:26 am
by leilei
Virtualizing CPUs through brings unpredictable variables from hardware that can be out of reach and hard to debug. Also that's like the thousandth time VM'ing was suggested...

Re: is it possbile to develop emulation-virtualization hybrid?

Posted: Mon 26 Sep, 2022 6:40 am
by Arjen42
Maybe it would be good idea to create PCem faq or something similar sticky topic in which these questions are explained.

Re: is it possbile to develop emulation-virtualization hybrid?

Posted: Thu 29 Sep, 2022 7:57 pm
by tk421
I do not believe this can be done at present, but given the big differences between virtualization and emulation software, I would think there is no need for such a hybrid program to be developed.

PCem is radically different from virtualization solutions like VMWare, VirtualBox, Microsoft Virtual PC 2007 and other programs that fulfill virtualization needs. Emulation software like PCem emulates specific computer hardware, which makes it so valuable compared to VMWare, among others.

It all depends on which programs you are trying to run in a VM. Most XP-related tasks are best left to either your modern PC itself, or virtualization software like the ones mentioned above. Virtual PC 2007 is not worth the effort on Windows 10 as it is too old for a modern PC. Both VMWare and VirtualBox have their advantages depending on the program you are trying to run on XP or newer versions of Windows or Linux.

Re: is it possbile to develop emulation-virtualization hybrid?

Posted: Wed 16 Nov, 2022 8:42 am
by MichaelJManley
Yes, this is something that comes up over and over and over.

PCem will NEVER be a virtualiser. The whole point of PCem is to emulate the hardware and basically give you a 1 to 1 copy of older hardware, even to the bios/chipset level.

Emulation != Virtualization.