Phenom II X4 940 Black Edition Memory compatibility

You need to look at the specs for the motherboard. That should tell you what memory speeds are supported.

Already did. The motherboard manual only specifies the maximum speeds and that it supports 667 memory - but it doesn't say what memory it requires for a certain cpu type.

Basicly it's just a matter of telling me the fsb of the cpu unit, as I know you can't go below a 1:1 ratio

What exactly is your motherboard? Most MB makers websites can tell you what CPUs and/or memory that are supported. Look for a "Qualified Vendor's List" or QVL for the memory.

This is a motherboard issue, not CPU dependent.

ASUS M4A785D-M PRO

But those lists aren't useful. They list what memory and what cpu is supproted, sure, but not which memory is supported with what cpu.

Anyway I've accepted the offer, and I'll figure out the answer to my question next week. I'll simply see if I can select a slower speed in the bios and boot   and if not I'll order 2x4gb memory and problem solved.

For what it's worth, you can run faster memory at slower speeds with no problem. Again, memory support is motherboard dependent, NOT CPU. If the motherboard supports the memory, it will do so with ANY cpu it also supports.

I know that mate. I just don't think you understand what the question is.

You see, you can NOT run memory at lower clock speeds than your run your processor. This means that a cpu with a 333 mhz fsb (e6750 for instance) requires ddr2-667 or faster memory and cannot run with 533.
I don't know much about phenoms, so I don't know their fsb. But if their fsb is higher than 333, 667 memory would not work. Anyway it doesn't matter. It's very likely that 667 memory will work, and if not I'll simply buy some new dimms.

ps. the memory controller is in the cpu since athlon 64, which means the motherboard dependancy is limited to socket placements.

In any event, thanks for your time, but I don't think you understood my question.