Xen currently runs on the x86 architecture, requiring a ``P6'' or
newer processor (e.g. Pentium Pro, Celeron, Pentium II, Pentium III,
Pentium IV, Xeon, AMD Athlon, AMD Duron). Multiprocessor machines are
supported, and there is support for HyperThreading (SMT). In
addition, ports to IA64 and Power architectures are in progress.
The default 32-bit Xen supports up to 4GB of memory. However Xen 3.0
adds support for Intel's Physical Addressing Extensions (PAE), which
enable x86/32 machines to address up to 64 GB of physical memory. Xen
3.0 also supports x86/64 platforms such as Intel EM64T and AMD Opteron
which can currently address up to 1TB of physical memory.
Xen offloads most of the hardware support issues to the guest OS
running in the Domain 0 management virtual machine. Xen itself
contains only the code required to detect and start secondary
processors, set up interrupt routing, and perform PCI bus
enumeration. Device drivers run within a privileged guest OS rather
than within Xen itself. This approach provides compatibility with the
majority of device hardware supported by Linux. The default XenLinux
build contains support for most server-class network and disk
hardware, but you can add support for other hardware by configuring
your XenLinux kernel in the normal way.