Purpose: computation (C++ program), a lot of computation, each computation will last 12 hours or even longer, will run multi threads at the same time. Need up to 16G ram for the ram.
Configuration: no overclocking, no upgrading in the future
Which one is better regarding the performance?
Any advantage from more expensive E5540 based workstation?
What motherboard and RAM or system? A Xeon 5540 normally is used with a workstation/server motherboard and, unlike the i7, it supports ECC memory. Server type memory (and one or two Xeon processors) would be better if you need 16GB. It would be somewhat difficult to build an i7 based system with more than 12GB of RAM.
The 5500 serie Xeons are meant to be used in DP (dual sockets) server and workstation, hence the double QPI links, if you don't need 8 physical cores plus the 8 virtual cores from HT, you might as well stick to a much cheaper i7 platform.
Then again, with only 6 memory slots on single socket 1366 mobos, you'll either have to settle for 12GB or be prepared to cough up some serious dough for 24GB since that implies 4GB modules.
Actually, if pick E5540, I will pick dell precision 5500. If i7-950, I am thinking of HP HPE-180t.
They are very different systems that are not targeting the same market. The Dell is a workstation that can be upgraded to dual CPU and it supports ECC memory. The HP certainly is a fine end-user PC. If you select the Dell, have you considered buying a dual E5520? If your application can take advantage of up to 16 threads, it would be significantly faster than an E5540.