GA-P55M-UD2 Memory Timing Issue

[Potzy]

Good Afternoon TweakTown Techs,

Background
In Jan 2010 - I built two identical gaming PC's using components purchased from Computer Hardware - Scan.co.uk as recommended by Custom PC Magazine (at that time).
Based around Intel's SandyBridge CPU - I purchased two each of the following:

• Gigabyte P55M-UD2 Rev 1.0 Motherboard
• Intel i5 750 @ 2.67Ghz Socket 1156 LGA Lynnfield 45nm
• 2 x 2GB Corsair Dominator 1600Mhz 8-8-8-24 1.65v DDR3 (CMD4GX3M2A1600C8)
• Titan Fenrir CPU Heatsink/Fan
• Corsair HX750W Modular PSU
• Thermaltake Tsunami Dream Case
• Gainward Geforce GTX260
• Samsung Spinpoint 500GB SATA2 HDD
• Microsoft Windows 7 64-Bit Home Premium

Both PC's have been running absolutely perfectly until recently when one exhibited random shutdowns and refusals to reboot to BIOS.
After swapping out and changing over each component from the working PC - I deduced there was an error with 1 stick of the Corsair memory which when tested in both machines proved to be faulty.
As the Dominator memory has a lifetime warranty - this was returned to Corsair and I am awaiting replacements.

Fast forward to today:

I purchased two kits of 2 x 4GB Corsair Dominator 1600mhz 9-9-9-24 1.65v DDR3 yesterday from Computer Hardware - Scan.co.uk which arrived a short while ago and is now in both machines.

When I fitted the new 2 x 4GB DDR3 into slots 1 & 3 in my machine - the BIOS auto detected the change and asked me to review the previous BIOS settings which did not reflect the current Hardware status - I literally entered the BIOS pressing DEL - accessed the MB Intelligent Tweaker (M.I.T) screen and pressed F7 to Load Optimized Defaults. Additionally I changed the Extreme Memory Profile (X.M.P) to Profile1 - pressed F10 and allowed the PC to boot me windows. No problem whatsoever. I can see the 8GB memory running at 1600mhz with timings of 9-9-9-24.

Here is where the problem lies - when I fitted the other 2 x 4GB DDR3 kit into slots 1 & 3 in my sons identical machine - the BIOS refused to load and all that happened was short bursts of fan every 2 - 3 seconds. No beeps. No video output - nothing. I turned the power off at the rear of the case, removed the kettle power lead and reset the CMOS by shorting the CLR_CMOS pins just above the Front USB connectors. I reconnected the power lead, switched it back on and eventually (after repeating the CLR_CMOS step another 3 times) managed to get the BIOS to post. Strangely, even after setting each BIOS screen to reflect the settings on my machine - my sons PC refuses to boot, we just keep getting bursts of fan every 2 - 3 seconds.

I've tried the memory set aside for his PC in mine without any problems. The memory initially installed in mine refuses to boot in his.

As I write this post, we've just managed to get his PC to boot into windows using 'Fail Safe Defaults' which has left his memory running at DRAM Freq 533mhz with timings of CAS# Latency 7 clocks, RAS# to CAS# Delay (tRCD) 7 clocks, RAS# Precharge (tRP) 7 clocks, Cycle Time (tRAS) 20 clocks - Command Rate (CR) 1T
His CPU Bus Speed reads 133.2Mhz, Rated Bus Speed 2398.4mhz, Stock Core Speed 2666Mhz
, Stock Bus Speed 133Mhz - with an average temperature of 38 degrees Celsius.

If we try and load optimized defaults the PC refuses to boot / post BIOS.

I am now totally lost as to what to do next - can you please help?

[wazza300]

try with just one stick of ram installed,then test each stick and ram slot one at a time to try and find if a memory stick or slot is faulty

you could need more qpi/vtt for the integrated memory controller inside the cpu,xmp doesnt always set the right voltage as it depends on each cpu's memory controller in how much voltage it needs ect