You did not state which form factor you have but the following should help.

https://www.dell.com/community/Desktops-General-Read-Only/OptiPlex-760-CPUs/td-p/3958116

Optiplex 760 Tech Guide 

Hi @Phippy,

It's not said what size your 760 is - MT, DT, SFF, or USFF?  I'm guessing it's not an MT due to 235w PSU.

All models of the 760, except the USFF, can take the C2Q Q9650.

Since you just got that 760 and it's a bit older, you might try a new size 2032 CMOS battery.  Meanwhile, you also try removing the current battery, wait about 10 min., and re-install.

The problem you're having is not jumper related that I know of.  Also, the Tech Guide doesn't say you can use the Q9650 per a certain MB your 760 may have.  It's just the USFF that can't take the Q9650.

Also, you were right about updating the BIOS first.  I double-checked and was a bit surprised A16 is the latest BIOS for the 760.  The latest BIOS for my 755 is A22.  I guess that's Dell for ya'.

May be @JOcean will have more ideas?

Hey, thank you for the reply!

The unit is a SFF. I went ahead and tried the CPU while i was waiting, but it gave an "Unsupported CPU detected" message. Again, without any motherboard documentation, i don't know if that's that, or if there may be a jumper or something i am simply over looking. Any ideas?

good call in the 2032 battery. I pulled it out, and waited 20 min. I then turned it on without the battery, and then with the battery, but the same results with same error message. (Yes, the power cord was disconnected along with all other external cables during the 20 min.

So i am back to square one. it seems =/

From the link I posted and further down the replies was this one from speedstep which I failed to see earlier.

"SFF and USFF do not support quads. Power supply is too small and does not have a 375W upgrade.

The smith tower has 305w power supply usff has 230w power."

Bradthetechnut mentioned an opti-755. Does the SFF 755 support a quad? If so I can pick that up. Otherwise I’ll end up with an hp.

Un supported due to power supply and motherboard regulator issues.

Other Dell models like Inspiron 530 for example have 350W power supply when there is a quad core cpu.

Even Optiplex 755 models require 305W power supply for core 2 quads.

The  DT SFF USFF power supply does not support Quads.

You are limited to

Intel® Core™ 2 Duo E8600/3.33GHz, 6M, 1333FSB

Only the Tower Does and only with specific Motherboards.

The Optiplex 760 MT uses two motherboards -
T674K Non-Quad core CPU motherboard
U562N Quad core CPU motherboard

Intel® Core™ 2 Quad Q9650/3.00GHz, 12M, 1333FSB

You  you cannot use a quad core CPU on it.

38G73 E7400, 2.8GHz, 3MB, WFD, R0, (With VT)
F31F5 E7500, 2.93GHz, 3MB, WFD, R0, (With VT)
06YMG Dual Core E7600, 3.06GHz, 3MB, R0, (With VT)
H399J Dual Core E8400, 3.0GHz, 6MB, 65W, E0, 1333FSB
D923J Dual Core E8500, 3.16GHz, 6MB, 65W, E0, 1333FSB
N654J Wolfdale Processor E8600, 3.33GHz

Ok! Thank you all for the amazing help and support with this issue. I’ll have to see about swapping out the dell for the hp system and hope the larger power supply will let me swap out the cpu.

thanks again

phil

Optiplex 755 Tech Guide 

How does a person believe that the 760 or 755 DT or SFF do not support quads when it's in the Tech Guide that they do?  It doesn't say any other modification required to support the quad.  Why would Dell print that if it's not true?

Hi again @Phippy,

If you find that the CPU doesn't work in another PC that should be able to take it within specs, you might have a bad CPU.

According to the tech guide, only the USFF model of the 755 doesn't support a quad.

Also, MT's are better for modifying than SFF's.