You will have to contact dell and ask what processors are supported by their bios. Then, you can select from those processors.
However, upgrading a PC that has a q45 chipset and 280w power supply will, in my opinion, not be worth it. It will still not be supported by Windows 10 (which will inevitably will be installed by Microsoft), which will force you to add a graphics card which (if you succeed in compatibility) will force you to get a new power supply (if the power supply will be compatible).
Best advice - Just get a current motherboard, processor, memory, psu, and avoid the problems you will be facing.
I didn't think Dell would be helpful since the unit is not under warranty and an"official" response from Dell will most likely come from the same tech guide that I already have which lists the E7400 as the max CPU. I was hoping to hear from someone who has actual XE experience with the E8400, Q9650 or Q9550S.
E8400 CPU's are only $10 so the XE (as is) is worth upgrading so long as the combo is stable. Upgrading the MB and memory is not cost effective and Windows is irrelevant.
Thanks for the reply
The problem is that, for those other processors, if they are not supported by Dell's bios, they may or may not work, or perform correctly, and may even damage your motherboard. Only Dell can tell you what processors are supported by their bios.
I called Dell... Zero help. I was transferred 4 times and the last unintelligible person was finally willing to answer my question. He told me the processor could not be upgraded. He said the MB, processor and memory would have to be replaced.
The Dell Tech Guide lists one motherboard and three different processors that are compatible so that tells me the processor can be upgraded.
Doc, I understand what you are saying and I appreciate your responses.
It will be difficult to get Dell to give you the information.
The E7400 uses socket LGA775:
There are at least 176 processors that fit that socket:
This is why Dell must give you the answer. The only other solution I can offer is that someone on the Dell support forum may have more information on your particular Dell BIOS.
Thanks to everyone who replied.
I posted in the Dell forum and someone was kind enough to provide the info below:
The E8600, Q9550S, and Q9650 were not tested by Dell on this model. I can show you what the Dell tested parts page list for this model =
4HF4Y Wolfdale E5300, 2.60GHz, 2MB, 65W, R0
38G73 Wolfdale E7400, 2.80GHz, 3MB, WFD, R0
H399J Wolfdale E8400, 3.00GHz, 6MB, 1333FSB, 65W, E0
N1MFN Xeon Westmere X5650, 2.66/6.4GHz, 12MB, 95W, 6C
The latest Bios A05 (OXE-A05.EXE) only mentions as a fix, "Support Windows Signing function". It does not mention fixes for other supported CPUs.
Since I already ordered the Q9650, I tried it anyway. The cores reach 84C within three minutes of starting the Prime95 stress test and 94C within another minute so it's a no-go I'm thinking any 95watt CPU is going to run too hot for the XE.
Since E8400 dual core CPU's are dirt cheap on eBay, I ordered one and it runs just fine in the XE.
I have an OptiPlex 780 I'm going to try the Q9650 in, next. Luckily, I was able to find/order an OEM copper heatsink with tubes for the 780 that will hopefully keep the temps down.
The copper heat-sink does better.
30-34C at idle and 59-66C with Prime95 stress test.