There is no once and for all because there is no one size fits all [NAME]-Chris M  might have more information. OptiPlex 760 MT LGA 775 Socket T  The Optiplex 760 MT uses two motherboards -T674K Non-Quad core CPU motherboardU562N Quad core CPU motherboard DESKTOP USES    R239R, D517D, M859N  Dont know which one  if I venture to guess I would say M859N [IMAGE]M869N SFF M863N supports QUAD no other. Fastest supported CPU on NON USFF is Intel® Core™ 2 Quad Q9650/3.00GHz, 12M, 1333FSB  DT MT SFF seem to support this but it does not go into WHICH BOARDS and HEATSINKS and RAM support this. [URL]     There are versions of the BIOS and board and power supply and heatsink and Ram that support quads  with 1333MHZ FSB and there are versions that DO NOT. its not one piece or one size one and done. There are many PARTS
I have read many threads on this forum about upgrading from an Intel Exxxx series cpu to a Qxxxx series quad core.  Some say it can be done, some say not.  Some say only the MT model can handle a quad.  Some of the supporting motherboard numbers are listed for MT in the forum but not for DT.  I have a MB that is not listed in any of the forums, 0R230R in a 760 DT.  The DT only has a 255 watt psu and some say that is not enough wattage to run a quad, some say it is.   The heat sink also comes into play.  There are 2 types of heat sinks for the DT model, one is for Quad and one is for Duo 2 cores.  Those part numbers are readily available on the form or via net search.   Can someone with some advanced knowledge or practical application knowledge finally put this issue to rest? Will a Quad Core Intel Q9000 series run in a Optiplex 760 DT model with a 0R230R motherboard and a 255 watt psu??  If not, are there any motherboards for the DT model that will run an Intel Q9000 series cpu?  Will the heat sink need to be upgraded to the copper tube type if a quad is installed?  
Once and for all, can someone clear up the confusion about a Quad upgrade in a 
Optiplex 760 DT model??