I've been searching the web to no avail, I wanted to know if anyone is running ESXi 5.5 on this server. I have the opportunity to purchase some of these at a very reasonable price.
I was able to do find https://www.vmware.com/resources/compatibility/search.php compatibility information based on the system board (S5400SF). I noticed that ESX 4.3 U3 was the last Operating System version that was tested by WMware for this product.
Intel always recommends using http://www.intel.com/support/motherboards/server/s5400SF/sb/CS-028454.htm validated Operating System to avoid unforeseen issues.