Hi Shaocaholica,

Did you update to the most current BIOS prior to installing the new CPU?

Yeah I'm on the latest bios (A18 from sept. 2013).  Although I've seen screenshots of the 960 SFF running the Q9650 with much older bios versions.

Here's a bios screenshot of another SFF running this proc:

Just received a replacement motherboard off ebay.  Was told by the seller that it might have had a quad core in it but wasn't sure.  Just installed it and still didn't work with my Q9650.  Got the same error, "unsupported CPU".  I'm going to straight up buy a whole 960 SFF with a factory installed Q9650 and find out whats causing this incompatibility.

There are different motherboards AND different power supplies.  Not all boards and all power supplies support all processors. The Q9400 seems to be fine across the line. What is the part number of the board you are using? What is the S Spec of the processor you are trying?

http://www.dell.com/downloads/global/products/optix/en/desktop-optiplex-960-technical-guidebook-en.pdf

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

Intel Core 2 Quad Q9550/2.83GHz,12M,1333FSB

Intel Core 2 Quad Q9400/2.66GHz,6M,1333FSB

There is a K075K.

http://ark.intel.com/products/spec/SLB8W

SLB8W should work.  However it could be that its actually a remarked CPU 80569PJ080N aka a QHGF

Intel is cracking down on Remarked Engineering Samples.

For the SFF, I've only been able to find one part number for the mainboard which is part number 0G261D.  Including the spare board I bought I have 2x0G261D's right now and both don't work.  As for the CPU, it has sspec SLB8W.  This is -my- actual CPU:

AFAIK, Intel only made this in a 95W version and only one stepping.

Also, here are screenshots of various Optiplex 960 SFFs bios screens showing they are running the Q9650.  If you look up the service tag, you can confirm they are indeed SFF units from the PSU and heatsink part numbers.  Plus the auctions I found these screenshots from also have pictures of the chassis clearly showing they are SFF.

http://imgur.com/a/zy8FZ

So I bought another off-lease 960 SFF that was originally configured from Dell with a Q9650.  I know this because I checked the service tag.

It arrived today and when I booted up the quad core was correctly shown in the bios and in windows with no errors as expected.  I popped the CPU out and its the same stepping as the CPU I had trouble with in my first 960 SFF.  Maybe my first CPU was bad so I put it into this new 960 SFF.  Works fine so it wasn't the CPU.

The mainboard part number between the 2 machines is the same. G261D.  I'm still trying to scour the mainboard for identifiers but nothing is showing up.

The PSU does have a different part number but the total wattage rating is the same and each voltage rail has the same max amps rating.

The next test I'm going to do is swap the mainboards which in essence is swapping the PSU and see if it makes any difference but I'm pretty sure its a variation in the mainboard.

FOUND THE PROBLEM!

Turns out it was the heatsink but not in any meaningful way.  At first I looked at both heatsinks to see if they were the same physically and they were.  Both used 3 heat pipes and were tower design.  The heatsink part numbers are complicated.  The heatsink is 2 parts, the tower and the shroud.  I think Dell has part numbers for the tower, the shroud and the assembly of the 2.  Anyway physically my heatsinks are the same and the fans have the same CFM/wattage rating but the shroud has different part numbers.  Now this shouldn't be a problem as there's no way for the mainboard to know which is installed, however it does know.  The bigger fan header is different between the 2.  On the version that DOESN'T work with quad cores, the last pin of the header is grounded with a jumper.  Basically does nothing other than to identify it as a different fan.  The version that works with quad cores has the last pin empty and unconnected so not grounded.  Thats the ONLY difference.  When I put the new quad capable heatsink assembly into my original 960 SFF, it now works with quad cores.  I'll post pictures of the fan connectors later.

I'm not sure what Dell was trying to do.  They clearly put in a mechanism to identify different heatsinks but why?  Why not have 1 type of heatsink that works with ALL procs to avoid this kind of confusion?  Simplify manufacturing and inventory.  Why are my identical heatsinks setup so that they are identified differently?

SHAOCAHOLICA, thank you VERY much for your information!  Can you take pictures of your fan connectors and upload them here?!

If you can't, do you have the model numbers?

Thank you!

Here you go:

Hi, the image suggest that DW017 can also be modified. How is it possible?

Thanks in advance

The only difference is a jumper wire.