Multiple physical CPU's? as in multiple processors? Never heard of this outside of the EVGA mobo which sets 2 cpus...not sure. I would say for regular gaming and household use, an AMD 960T/955BE or an intel i5 2500k is the best setup for your needs. 1 Processor, multiple cores. nothing else to say outside of the multiple processor would cost so much money, its not worth it. The board alone for this is $580, then the processor on top of it. No way!
A current generation multicore has separate physical cores.
So, a quad core AMD would = about the same performance as 4 single core AMD cpus.
Except for the fact, that the multi CPU setup would require 4 times as much energy, and would be incredibly expensive to build, and probably would not have the same clock speeds.
Multi Socket Boards are designed for servers, and are incredibly expensive to build, and do not offer any bonus for gaming.
If you want to game get a solid 4core processor, since games can not use more than 4 cores right now anyway.
I came across a site selling multi-socket mainboards, from manufacturers such as EVGA and Tyan, which ranged from two sockets to four sockets (and even up to 32 slots for RAM) supporting up to 6 cores per CPU.
I know they are marketed mainly for server use and realistically, the offerings on that site are priced high and require dated CPUs - Opterons and Xeons from 2009, slow RAM so if one were to build two computers for comparison, I would image the newer single-physical-multicore-CPU with faster RAM would be a much better investment.
However hypothetically speaking, would such a set-up yield any significant advantages over a single physical CPU?
In a server/workstation environment the advantage of using multiple CPUs is that each processor will have its own bus with dedicated memory to that processor. So with something like high end video creation you might find that the dedicated bus can make a difference but most of the time it really wouldn’t make much of a difference.
Multi CPU boards are meant for workstations and servers that are running applications that can make use of more threads than a single CPU has available. FSX is the only game i know of that can make use of more than 4 cores and show any meaningful difference so a multiprocessor board will not help at all for gaming as a single 2500 is more than enough, and it might even hurt performance if the OS doesn't distribute the threads ideally across the two physical chips as there are larger buses involved which have long latencies than the internal buses in a CPU.