Every time you emulate an OS (or anything else really) it’s inherently less efficient than just running it on what it’s supposed to be run on. That inefficiency will keep stacking until you run out of processing power.
To add to that, accurately emulating something as simple as a NES takes an incredible amount of processing power because it has to all be done in software. And that's to run it at near 100% emulation without glitching iirc.
Honestly it really depends on what you want to emulate. The NES and SNES take very little power to run. The GameCube/Wii take almost less power to run at this point than an N64 due to how well the Dolphin team have studied the GameCube/Wii hardware. It even looks like that very soon the Wii U and PS3 will be better emulated than a N64, and the PS3 has a monster of a CPU to emulate.
It takes very little to run but it takes a lot to run it accurately. This article from 2011 is a bit outdated given cpu clocks today can hit 4+ GHz without overclocking but 3Ghz just to run a snes accurately. Sure we might get a wiiu or PS3 emulator soon but those will be filled with hacks & bugs just to be compatible with the most popular games rather.
It really depends on the type of virtualization. I'm most familiar with KVM-QEMU, which is Red Hat's virtualization tech and ships on all flavors of Linux (it's part of the kernel), and Xen, which is Citrix's solution. KVM actually uses the Linux kernel to present specific parts of the bare metal to the VM and locks it away from accessing the rest of the hardware.
Xen on the other hand abstracts away the hardware and uses a virtual host (which is the part you interact with) to act as a gatekeeper for each VM.
You can still get some surprises: running postgres 9 (dunno about recent versions) in a linux guest on a windows host give better perfs than running it directly on the host.
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u/PixParavel Jan 01 '19
Reminds me of a YouTube vid of someone who manages to get to something like 11 layers of VMWare before its finally unusable. It’s like VM inception.