Hi all FF96 here!

So it seems that the Fujitsu Siemens Esprimo P5925 I bought bak on ebay in 2017 and as the beginning of this year I wanted to make it into a suitable gaming PC for the majority of games that will run on Quad core CPUS. The PC came with an Intel Core 2 Duo E6550 that has 2.33Ghz. The RAM it came supplied was 2GB and is upgradable up to 8GB DDR2 RAM.

Intel Core 2 Duo E6550 has a LGA 775 socket mobo fitting type and I did a search for a LGA 775 socket compatible QUAD core CPU with at least 3Ghz clock speed. This led me to getting the Intel Xeon X5450 3.00Ghz hoping that will superboost the P5925.

I also got 4x of 2GB ram cards to upgrade the capacity of the RAM.

When the X5450 CPU and 8GB RAM were in place, the PC was unable to boot up as it was showing absolutely NOTHING on the screen, followed by the fan speeding up. I did put the heatsink and thermal paste back on by the way.

At first I thought it was the RAM cards that were not seated properly but after reverting back to the Core 2 Duo E6550 CPU the PC was back to normal!

This is totally baffling me because if the X5450 QUAD Core CPU has the LGA 775 socket type as the E6550, then why is the mobo not liking it?

Any help would be greatly appreciated

FF96

Hi FF96,
The LGA775 CPU socket was in widespread use for quite a while and just because it fits in the motherboard socket does not mean it will actually work and be supported with the current chipset and other supporting hardware. I am in the US so I am not familiar with Fujitsu Siemens computers, I searched Google and I found a spec sheet (Which I think is what you have). There is also sometimes a CPU power limitation and being a pre-built computer this can be a big problem as the heat-sink and motherboard VRM's are only capable of (Possibly) supporting a lower power chip. I found This document that lists the supported CPU's for the Q35 chipset

I have an HP DX7300 microtower PC. I tried upgrading the CPU to a C2Q Q6700 but it turns out the processor wasn't compatible with the board. It's probably something similar here.

X5450 is a Xeon CPU for LGA771 socket (for servers), it's not supposed to go into LGA775, and normally the 2 Plastic keys that direct the CPU position prevent it from going in

Less officially, the electrical difference between LGA771 and LGA775 is just in 2 swapped pins. There are adapters available (a film with 2 contact points, that provides the swap between the pins, that you stick on the CPU) to be able to plug the Xeon CPU into LGA775 (after breaking off the Plastic keys), but only few of the LGA775 chipsets support such hack anyway

So either get a desktop Core 2 Quad Qxxxx CPU, or do the Xeon hack correctly with the adapter. Anyway, double check what your chipset is and whether it supports the CPU you want

Hi there Ash

Yes the Xeon CPU which I obtained from ebay was actually modified by the seller (both pin switching and the cutouts made on the corners) and was mentioned as a 775 mod for a 771 server CPU. After looking to why the Xeon refused to work on my Fujitsu Esprimo P5925 mobo, it turned out that the chipset (Q35) does not support the X5450 Xeon CPU. I need to refer back to that table of which Xeons are compatible. My only last hope is either by luck finding another Xeon processer that can happily accept the 775 socket and the Q35 chipset. Or I can find the best Quad core of the Intel Core 2 series with the highest Ghz it can offer!

I would have changed the mobo for one that would suit the AMD Ryzen CPU lot but there is one big issue. The P5925 door is on the right side, therefore it the left side mounting for the mobo. Most motherboards of similar/same size are designed to be for the right side mounting position.

Most mainboards for PCs that open on the right side are either :

 - Ordinary *ATX boards installed upside down (with the PCI slots above the CPU). In this case you will be able to fit most ATX boards

 - BTX boards - a format which is standardized by itself, but not compatible with ATX. In BTX boards the CPU socket is positioned diagonally and in a way that lets the CPU fan draw air directly  through the front of the case. To the best of my knowledge BTX was an Intel only thing



Things that can complicate replacing boards in "brand" PCs :

 - Standoffs for the screw holes are embedded into the case and cannot be moved, so if there is a redundant one (where the board is not meant to accept it) you have to isolate it so it won't short to the board

 - Sometimes there are standoffs provided in a specific location for the CPU cooler screws as well, which may not line up with the new board

 - The onboard connectors shield might be embedded into the case (not a separate part) so not match the positions of ports on a replacement board

 - The pinout of front switches/LEDs/USB connectors that come from the case may not be standard. Sometimes pinout of the power supply (the 24 pin) is not standard either



Q35 would i think support most Core 2 Quad CPUs..  But here is one more thing : How old are the games you want to run ? Some old games don't really benefit from a quad core CPU, they would run better with a dual core (as long as it is better in something that the game does benefit from, like simply higher clock frequency)



It would probably make little sense to run Windows higher than Win7 on a 775 system..

If you would want to run Linux on it then ask away (I use Linux on several PCs mostly Core 2 Duos)