Memory And FSB Not the same why ?

Hello guys , I have a question .
My uncle bought new PC which i recommend him , And i set everythig .
Now

In bios The FSB IS 266 (CPU IS E74000)
SO 266 X 10,5 = 2.8GHz
Memory i installed DDR2 800 X2 Chips

And i know it supposed to run at 1066 mhz cause ddr2 533 will be enough so why does it runs still at 800MHz and not as the FSB 1066 ?

Thanks for any help .
But it

M\B
EP43-UD3L s775 C2Q 1333Mhz

CPU
E7400

Mem
Kingstone
DDR2 800 Value

You bought 800 ram so its running 800, if you wanted the ram to run 1066, you should have bought 1066 ram.

You could try to overclock the ram by setting it manually to 1066 in the Bios, but the odds are it will not work.

While the CPU and memory buses could operate at the same frequency, they don't have to. See Wikipedia for good explanations of the difference between the two: http://en.wikipedia.org/wiki/Front_side_bus#Memory

DDR2 533 MHz is 266 MHz x 2. DDR2 1066 is 533 Mhz x 2. DDR2 1066 memory often is overclocked 800 MHz memory that requires more voltage and lower timings.

A memory at 533MHz X 2 Chips In dual channel will create 1066MHz FSB , Isnt it ?

The answer is no. The FSB speed is set from your motherboard BIOS and not from you installing two memory modules. If that was the case, I could install two 1066 MHz modules and expect my system to run at 2132 FSB?

You installed DDR2 800 MHz memory so they will run at 400 MHz stock without OC'ing just like all DDR2 mudules are designed to do.

But the performance improvement with 10600 MHz memory will be 0-1.5% at most. Is it really worth it? Spending money on a faster CPU or GPU usually is a better investment.

If it's the same memory (and it often is), then the timings might be 4-4-4-12 at 800 MHz and 5-5-5-15 at 1066 MHz. The higher timings offset part of the performance gains. Besides, you can overclock quality 800 MHz memory yourself. Just increase the voltage and timings and make sure that it's stable. It might not reach 1066 MHz, but it could run very close to it and it's free.