Introduction
Intel has launched two Pentium 4 CPUs – 672 and 662 – supporting the new Intel Virtualization Technology (VT). Formerly known as Vanderpool, this technology enables a CPU to act as if it were several CPUs working in parallel, in order to enable several operating systems to run at the same time in the same machine. In this tutorial we will explain everything you need to know about this new technology.
Virtualization technology is nothing new. There is some software on the market that enables virtualization and probably VMware is the most famous one. With this technique, a single CPU can act if it were several CPUs running in parallel, allowing the system to run several operating systems at the same time.
You may confuse virtualization with multitasking or even with HyperThreading. On multitasking, there is a single operating system and several programs running in parallel. On virtualization, you can have several operating systems running in parallel, each one with several programs running. Each operating system runs on a “virtual CPU†or “virtual machineâ€. And HyperThreading simulates two CPUs were there is just one physical CPU for balancing performance using SMP (Symmetric Multi Processing), and these two CPUs cannot be used separately.
But if there are software like VMware that enables virtualization, why implement Virtualization Technology inside the CPU? The advantage is that CPUs with Virtualization Technology have some new instructions to control virtualization. With them, controlling software (called VMM, Virtual Machine Monitor) can be simpler, thus improving performance compared to software-only solutions.
How It Works
Processors with Virtualization Technology have an extra instruction set called Virtual Machine Extensions or VMX. VMX brings 10 new virtualization-specific instructions to the CPU: VMPTRLD, VMPTRST, VMCLEAR, VMREAD, VMWRITE, VMCALL, VMLAUCH, VMRESUME, VMXOFF and VMXON.
There are two modes to run under virtualization: root operation and non-root operation. Usually only the virtualization controlling software, called Virtual Machine Monitor (VMM), runs under root operation, while operating systems running on top of the virtual machines run under non-root operation. Software running on top of virtual machines is also called “guest softwareâ€.
Conclusions
From Intel datasheet: “Intel Virtualization Technology requires a computer system with a processor, chipset, BIOS, Virtual Machine Monitor (VMM) and for some uses, certain platform software enabled for it. Functionality, performance or other benefit will vary depending on hardware and software configurations. Intel Virtualization Technology-enabled BIOS and VMM applications are currently in development.â€
In summary, as far as we know, there is no VMM software for Intel Virtualization Technology yet. So if you buy a VT-enabled CPU today, you will have to wait for Intel to release VMM software and also for the motherboard manufacturers to release VMM-enabled BIOS (or at least certify that your current motherboard BIOS works fine with VT).
One question that is still unanswered is if VMM software for Intel Virtualization Technology will be given for free or if it will cost something. Just for comparison, VMware Workstation 5 costs between USD 189.00 and USD 199.00, so we hope that if Intel doesn’t give the software for free that at least they charge less than that for it.
On the good side VT promises to have a better performance than VMWare, but we will have to wait until VT VMM software reaches the market to check if this is really true.
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