Does ESX 3.5 support 64 bit OS?

[gomats]

Actually we need to create 8 VM with windows 2008 R2 OS (64 bit OS)

The requirement for each Vm is 5.GhZ, 8GB RAM

What shold be the ESX host configuration (Like CPU, memory) for creating this  4 VM in each host.

[idle-jam]

Yes, ESX3.5 does support 64bit. This is assume that the host is 64bit ready and you will need to turn on Intel VT in the BIOS. I would always start with 1vCPU and then say 4GB of Memory and slowly scale up when needed to.

My worries is that putting too many vCPU for 8 VMs would make all the vCPU very busy and in return have reverse effect of being slower rather than faster.

[bulletprooffool]

Absolutely, yes... provided you are on e the correct update level (3.5u5??)

Have a look at the compatability guide for full details:

http://www.vmware.com/resources/compatibility/search.php?deviceCategory=software