Quoting from InfoWorld
I bet if I took a short and informal poll and said the majority of virtualization users were excited to hear VMware's announcement of 64-bit guest operating system support, most of you would agree with that statement. And following up on that statement, I would also bet that only a small minority of those same individuals would know exactly which processors offered compatibility and met the hardware requirements. Personally, I didn't even think about it. I just assumed I could purchase a 64-bit processor and then be on my way enjoying a fun filled afternoon with my virtual machine running a 64-bit guest operating system. After all, what's the problem?
After doing a little bit of reading and research, I was directed to a VMware knowledge base solution appropriately titled "Hardware Requirements for 64-Bit Guest Operating Systems". Exactly what I needed.
The question was simple. I want to use either VMware Workstation or VMware Server to run virtual machines with 64-bit guest operating systems. What are the hardware requirements for the host machine?
The answer was not so simple. As I feared, you simply cannot purchase any old 64-bit processor. But knowledge is power, and so I pass this KB article on to you, in the hopes that the answer can shed some light on the subject for those of you in the market to purchase new hardware in order to run these 64-bit guest operating systems inside your virtual machines.
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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)
Click here to read the entire article.