Hardware Requirements For 64-Bit Guest Operating Systems

 VMware's virtual machine monitor has traditionally used segmentation toprovide isolation between the guest operating system and the virtualmachine monitor. This is necessary because the guest operating systemand virtual machine monitor share the linear address space.

AMD
Segmentation support is missing from the initial AMD64 processors (thatis, revision C and earlier) while running in long mode. As a result,AMD64 processors prior to revision D do not have an efficient mechanismfor isolating the virtual machine monitor from 64-bit guest operatingsystems.

A limited form of segmentation was reintroduced in long mode, inrevision D AMD64 processors. As a result, AMD64 processors must berevision D or later to run 64-bit guest operating systems.

Note: Because AMD Opteron and Turion processors do not ship in revisionD, AMD Opteron and Turion 64 processors must be revision E or later torun 64-bit guest operating systems.

Intel
Intel EM64T CPUs do not have segmentation support in long mode. If theIntel EM64T CPU is VT-capable, it comes with hardware virtualizationsupport (Intel's Vanderpool Technology). This hardware virtualizationsupport allows Workstation and VMware Server to work around the lack ofsegmentation, making it possible to run 64-bit guest operating systemson Intel EM64T VT-capable CPUs.

32-Bit CPUs
Please note that Workstation and VMware Server require a 64-bit CPU torun a 64-bit guest operating system. While it is theoretically possibleto emulate a 64-bit instruction set on 32-bit hardware, doing so mostlikely results in unacceptable performance degradation.

VMware distributes a free utility that can be used to determine whetheror not your CPU is suitable for running 64-bit guest operating systems.You can download this utility from the VMware Web site atwww.vmware.com/download/ws/#utilities. VMware Server includes thisutility in its product distribution, so you don't need to download anadditional tool.

Workstation 5.5 and VMware Server 1.0 support virtual machines with64-bit guest operating systems only on host machines that have one ofthe supported 64-bit processors:

• AMD Athlon 64, revision D or later
• AMD Opteron, revision E or later
• AMD Turion 64, revision E or later
• AMD Sempron, 64-bit-capable revision D or later (experimental support)
• Intel EM64T VT-capable processors (experimental support)


Need a short answer for the question "Why Intel-VT/AMD-V for 64 Bit guests"? Here we go.

Running 64-bit binary translation requires "segment truncation"support. Modern OSes don't even use segments anymore, so both AMD andIntel removed segments from their x86-64 specs. Turns out VMware'sbinary translation technology does use segments ... AMD added limited(but good enough) support early on (RevC Opterons did not have it, RevDand later do) specifically for VMware; Intel does not support thesegment truncation feature, so on Intel VT is necessary instead.

Either VT/SVM or segment truncation can be used to protect the VMM frombeing overwritten by the Guest OS, but at least one of thesetechnologies is required. (We have internal builds that run withoutprotection, but they are used for benchmarks only and are unsafe forreal-world use).