System slows down with more RAM (4 sticks)

[jttb]

Motherboard: Gigabyte H67MA-UD2H-B3
CPU: Core i5 2500K
RAM: G.Skill Ripjaws F3-12800CL9D-8GBRL
OS: Win 7 Pro 64bit

I have been running this machine without problems since May last year with 8GB of RAM.

We are now using more virtual machines at work and seeing as how cheap RAM is we decided to double the RAM to 16GB.

When we added the second (identical to first) kit of RAM the system slows down to the point of not being usable (3 minutes to load Windows compared to the normal 20 seconds).

To clarify there are two kits of identical RAM. Each kit is two 4GB sticks. Two kits totals 16GB (i.e. 4 x 4GB identical sticks).

The system is fine with 1 X 4GB, 2 x 4GB and 3 x 4GB but as soon at the four stick is added it runs amazingly slow.

Tried swapping the sticks around to see if one (or more) of them is faulty with no luck. The behaviour is the same regardless of which sticks are used so therefore the RAM is not faulty.

Am currently running the system with 3 X 4GB sticks and it is fine but would like to get to the bottom of the problem.

Anyone seen a system slow to a crawl with 16GB RAM (i.e. all four slots used)???

Any suggestions would be appreciated....

[Tradesman]

A few possibles....do you have the latest BIOS? I'd check that first, next the sticks need to be set manually, so if you have XMP enabled, disable that and set your base timings to 9-9-9-24, CR (Command Rate) to 2T, DRAM voltage to 1.5 and check your VCCIO voltage, may need to raise that a little to maybe 1.15 or 1.2

[jttb]

Tradesman:

BIOS is the latest version.

Most of the settings were already set as you suggested. Just pumped up the VCCIO to 1.2 and no improvement.

3 sticks computer is fine.
4 sticks is the worlds slowest computer

[Tradesman]

Try DRAM at 1.55

[jttb]

The mother board didn't have an option for 1.55v so I used 1.56v as the closest option.

This did not fix the problem.

[GSKILL TECH]

Post pictures of BIOS

Thank you
GSKILL TECH

[jttb]

https://plus.google.com/photos/11710...CMfJyMSzy4ixKg

[Tradesman]

Looks like you have the DRAM at 1333 instead of 1600, though it's all set (timings wise) for 1600, may want to either raise the memory multiplier to get up around 1600 or leave at 1333 and tighten timings to 8-8-8-24

[jttb]

Changed timings to 8 8 8 24 and this didn't fix the problem.

Couldn't find an option to pump up the speed to 1600.

[jttb]

Update:

Just ran Memtest for two hours without any errors.

Problem remains in that as soon as the fourth stick is inserted the machine becomes super super slow.

[Tradesman]

Sounding like possibly the mobo or CPU, may want to check the CPU and socket to see if any thermal compound has seeped under CPU or into socket, also check for bent broken pins

[jttb]

Yes, I think we have tested the RAM enough.

I think it may be a motherboard/CPU issue.

Thank you for your help.