[SOLVED] Why does 800 MHz frequency RAM make my system unstable?

[maxfire92]

On paper, my system should be able to rock 8 Go on RAM running with a frequency of 800MHz.
So when came the time to upgrade my RAM this is what I've bought.
It used to be 4 Go running with a frequency of 667MHz.

With the 800 Mhz ram, in really, the system is stable doing office work, but crash (bluescreen) within less than 30 minutes when doing intense CPU work like the blend test of prime95 and gaming.
Since this is a prebuild computer, I ca not change the RAM frequency in the bios to reduce the speed to 667MHz.
So to reduce the frequency, I have to use a mix of old memory stick with the new one and I get 6go running at 667Mhz at every is stable.
I also tried 6go with only the new memory sticks which ran at 800MHz and it wasn't stable.
I've ran 11+ pass of mem86+ on the new memory sticks without any errors.
I also verified that it is running the latest Bios version released by the manufacturer.


How come I can't rock RAM running at 800MHz?
Is this fixable? What should I look at?

Here are the spec of my computers :

Operating System
    Windows 10 Home 64-bit

CPU
    Intel Core 2 Quad Q6600 @ 2.40GHz
    Kentsfield 65nm Technology

RAM
    8,00GB Dual-Channel DDR2 @ 399MHz (5-6-6-18)
    4 sticks of 2 Go (PC2-6400 DDR2-800MHZ 240pin Desktop DIMM)

Motherboard
    PEGATRON CORPORATION Benicia (CPU 1) 1.01
    BIOS    Brand    American Megatrends Inc.  Version    5.43

Graphics
    2048MB ATI Radeon RX550/550 Series (ATI)
    ASUS VP248QG (1080x1920@75Hz)
    ASUS VC239 (1920x1080@59Hz)
    ASUS VC239 (1920x1080@59Hz)

Storage
    465GB SAMSUNG HD501LJ (SATA )
    119GB KingFast (SATA (SSD))
    465GB Western Digital WDC WD5000AAKS-00V2B0 (SATA )

Optical Drives
    HL-DT-ST BDDVDRW GBC-H20L

Audio
    Realtek High Definition Audio

CPU-Z Memory tab
CPU-Z_SPD Slot1
CPU-Z_SPD Slot2
CPU-Z_SPD Slot3
CPU-Z_SPD Slot4
CPU-Z CPU Tab

Speccy SPD view
Speccy Motherboard view
Speccy CPU view
Speccy Graphics View

The computer is an upgraded HP Pavilion Elite m9458f bought at staple many years ago.
Here's an image of CPU-Z with mixed old and new memory sticks 6go stable setup. We can see that all number are the same except total ram amount and RAM frequency.

Edit : The new memory sticks are regular sticks and not dual channel memory stick.

 

[brispuss]

Not using memory from a certain dual channel kit is always risky. Often there are system problems. But sometimes use of individual memory can be accomplished (in dual channel mode and running at rated frequency) by making adjustments in BIOS.

However. Since this system is a basic pre-build, that usually means that many BIOS adjustments are unavailable to allow dissimilar memory to work together on the system.

Since suitable BIOS adjustments seem to be unavailable here, the best bet is to use 800 MHz memory from the same dual channel kit. This might require trying several kits until a compatible combination is found.

Here is some compatible memory.