[citation][nom]dgingeri[/nom]VT-d is hardware acceleration within the CPU for virtual machines. it has nothing to do with graphics. This is mostly used for (in home and/or regular user situations) virtual machines to run old software that won't run under the current OS, like running Windows XP software in a Windows XP virtual machine while the main OS is Windows 7, or running a Linux virtual machine on a Windows main OS. Most people won't be using it. If they do, VT-d won't make much of a difference for most people.I do, however. I use it to make multiple virtual machines to learn stuff for IT certifications. Right now, I'm working on my MCITP-VA cert, running multiple virtual machines from my home server (running Windows 2008 R2) so I can get a better job. VT-d missing would mean great trouble for me, if I were to use it as a server. Thankfully, if I were to get one, I wouldn't be using it as a server since I already have that.[/citation]
That is not entirely correct.
VT-x is the set of extensions required to properly secure a virtual machine running in long addressing mode and reduce VM reliance on operation emulation. It is the bare minimum required to run an OS safely in 64 bit mode on Intel CPUs (AMD CPUs can run 64 bit guest OSes purely in software but will still see performance benefits from AMD-V).
VT-d and AMD-Vi are the sets of extensions required to properly allow a guest OS access to peripherals without having to go through a software layer. This allows guests to access Ethernet controllers, USB controllers, PCI-E controllers, SATA controllers, etc... VT-d is to the chipset as VT-x is to the CPU.