1. Yes, that is correct. It does not have the option of a second CPU. 2. If you are talking about a different model of server - one that supports two CPU's - then yes, you could end up with the same processing cores and "roughly" the same performance with a 1x8 or 2x4, although heavy multi-threaded workloads will benefit from two physical CPU's over cores. 3. Memory Because the memory controller is now in the chip, more processors gives you access to more memory; a two-socket server will have two memory banks, each belonging to a processor, so if one socket is not populated, its memory bank cannot be used. Cost Fewer cores per chip is much cheaper, so if you needed 8 cores, 1x8 will likely cost $1000, while 2x8 would likely cost $500 (2x$250): 1x8 ($1100):[URL] 2x4 ($300x2=$600):[URL] (Also note that cache is usually attached to cores, so the fewer cores, the less overall cache, although the amount of cache per core typically stays constant.) Application If you are using some single-threaded application, then only clock speed matters, not cores, so it depends on what you will be doing.  Workloads like this aren't common but do exist. 
Just need a bit of help insuring I understand the processor, core, etc.  The Dell M620 Power Edge Server uses an Intel Xeon 2640 processor.  That processor has 8 cores, 20M Cache and 20GHZ clock speed. My understanding is that the Xeon is a sinlgle chip or piece of hardware that has multiple (in this case) 8 cores embedded in it.  Intel of course makes a huge line of chips that vary in core size clockspeed and cache size all of which drive performance. My questions are: 1. So the M620 box sold online with this processor is a server with this one chip and 8 cores.  This is a single processor (8 core) server, correct? 2.  My understanding is that 8 cores (along with speed and cache) are what ultimately drive performance. However, I could also configure a dual processor server with 2 x 4 core processors for about the same effect (holding cache and speed aside).  Is that correct? 3.  Holding total number of cores constant, what would be the rationale or advantages of going to one processor wiht more cores vs. more processors with fewer cores?  
Processors, Cores, etc