Member Avatar for Dougie

My Mobo is an Asus P5B Deluxe, Processor is a Core 2 Duo E6600 and RAM is dual channel OCZP800R22GK. This computer has been running for 1 1/2 years without a glitch. But I recently downloaded CPU-Z and it's telling me that my 800 mhz memeory's bus speed is presently running at only 400 mhz and the CPU's bus speed is 266.7 and it's rated FSB speed is 1066.7

Anyone have any idea as to why this is happening or am I missing something.

My Mobo's bios version is American Megatrends 0614.

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Short version for : what you and are seeing is expected — CPU-Z reports the raw oscillator/base clocks the board is using, while manufacturers advertise the effective transfer rates. That makes the numbers look “half” or “quarter” compared with the spec sheet even though the hardware is typically running as intended.

Quick checklist to verify everything is OK:

  • In CPU‑Z, check the Memory tab (DRAM Frequency) and the SPD tab to confirm each stick’s programmed SPD timings and rated speeds.
  • Reboot into the BIOS and look for DRAM frequency / memory ratio and the CPU base clock / FSB settings; confirm the board is using the rated SPD profile or the expected memory multiplier.
  • In Windows set the Power Plan to High Performance (or temporarily disable EIST/SpeedStep/C1E in BIOS) and run a stress test (Prime95 or similar) while watching CPU‑Z — this shows the clocks under load rather than idle-down values.
  • Run Memtest86 (one full pass) if you suspect memory instability after changing settings.

Why a RAM/FSB value can look lower than the “advertised” speed:

  • Motherboard auto-dividers will pick a slower memory multiplier when needed for stability (or when modules are mixed/mis-seated).
  • Mixing different DIMMs or populating wrong slots can force a conservative speed.
  • BIOS defaults and conservative SPD fallbacks will also do this.

If the system is stable and you see no performance drop, no action is required. If you want the RAM to run at its rated profile, set the memory multiplier/voltage/timings in BIOS to match the module SPD and test thoroughly. Avoid flashing the BIOS unless you need a specific fix, and make one change at a time while testing. Thanks to for the original clarification.

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Member Avatar for crunchie

The cpu_z is correct. Double Data Rate of 400MHz = 800MHz on the RAM. My cpu_z shows 533MHz for a RAM speed of 1066MHz.

6600's are quad pumped meaning that 266.7 = 1066.8

Member Avatar for Dougie

Thank you for your quick response. I'm still not sure that I'm completely clear on what you said lol!! So the " effective " CPU bus speed is 1066 but not a true 1066 mhz.??

Member Avatar for crunchie

I do not understand it well enough to give a decent explanation, but there is a good read here;
More about how to overclock, but you might glean something from it :)

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