Dated Tech Question LGA775 Pentium D

nevets_1917 · October 22, 2014

This is a first post so any feedback with regards to etiquette is welcome

This is sort of a CPU, PSU and MOBO question

I am working on cannibalizing an old HP SFF business desktop (dc7700) I think.

I have removed the Celeron D and replaced with a Pentium D (945 3.4Ghz). My concern is the PSU. The PSU built in was approx 250W.

The CPU side of the problem is, what is the best sort of number to work off with regards to power draw of the CPU. I am aware the TDP of a processor is the maximum thermal power released by the CPU and is probably not the best figure to go off but I wasn't too sure of an alternative figure. Some sort of guidance in this area would be appreciated.

PSU time, the TDP of the Celeron D was 84W vs the Pentium D 95W. I'd like to think an 11W difference wouldn't have any effect on the PSU (HP had ensured there was sufficient headroom) but being a commercial machine I have my doubts. Also I am currently only using a single HDD but would like to increase that (max 3) so spin up could become an issue (approx 25*3= 75W). I guess my question here is, is 250W sufficient to run a Pentium D 3HDDs (no optical) and 4-8GB RAM? I would like to add a graphics card so will most likely need to upgrade this???

Total Power Calculations so far (95W (CPU) + 75W(HDDs) + 28W (MOBO) + RAM??? + GPU???) = 198W (80% PSU Load)

The problem I have is I think (key word here) the PSU uses a 6pin CPU power socket (I may have been confused with the PCIE power socket) but I am fairly sure the MOBO has a 20-24pin (I have forgotten which one) main power socket and a 6pin CPU power socket. The reason I don't think it was a PCIE socket as there was only two plugs to the MOBO??? Do 6pin CPU sockets exist in the wild or are they a HP specific control thing. Because I am yet to see 6 pin CPU sockets

Any clarification on any of these matters would be great.

Thanks