Not all models support all processors for all versions.

Power Supplies and Heatsinks and Bios versions all come into play.

Unless you have a Full Tower and the Larger Power Supply it will not support quad cores.

There may also be versions of boards that do not due to VRM issues.

QX9650 is a core 2 EXTREME not a quad core.

Intel® Core™2 Quad Processor Q9650 is not a QX9650.

http://ark.intel.com/products/33921/Intel-Core2-Extreme-Processor-QX9650-12M-Cache-3_00-GHz-1333-MHz-FSB

http://ark.intel.com/products/35428/Intel-Core2-Quad-Processor-Q9650-12M-Cache-3_00-GHz-1333-MHz-FSB

 http://www.dell.com/downloads/global/products/optix/en/optiplex-780-tech-guide.pdf

The QX9650 IS a quad core processor.  Check the first link you posted and look at the "specifications" table for "number of cores."  it's 4.

The "X" simply indicates that this version of the Q9650 can be overclocked.  That, the FSB parity, and the Max TDP values seem to be the main differences that i could see from the charts.

Also I've thoroughly read the Dell Optiplex 780 Technical Manual that you posted the table from. The quad-core Q9650 is listed  under the mini-tower.  I've never seen a "Full" tower listed for the Optiplex 780.  I think the Mini-tower is the biggest size.

thanks anyways.

So the question still remains whether the over-clock-able QX9650 is supported by the Dell 0C27VV motherboard.  I thought with the few differences, it might be.

Marvin

I'm quitting on this project.  I've actually been trying to resolve this for 4 days now and the person i bought the processor from has offered a full refund since it was advertised as a Q9650 and i received a qX9650.  Too bad i can't use it, but...

so, i'm closing this post.