I'm slightly confused about 1:1 memory ratio

[staraxan]

I am about to purchase a new motherboard + cpu + memory to upgrade my old computer that is an Athlon 1 ghz (slot A) computer.

I have seen/read in reviews on the Nforce2 motherboards, and a few things that I have read, have left me slightly confused. I would like to fully understand a couple things, before I buy anything.

My question in this thread is about the 1:1 memory ratio, that is, running your computer's memory synchronous to the FSB.

If I get a nforce2 motherboard and set the FSB to 166, and set the memory ratio to 1:1, then which one of these are true:

1) Is the memory running at 166 mhz?

2) Or is the memory running at 333 mhz?

The reason I am asking this is that I have seen pictures of BIOS setup screens in some of the reviews I read, and in those pictures it has 1:1 memory ratio, and right under it, it will say "memory frequency 166 mhz".

This makes no sense to me. If the memory is really running at 166 mhz, then what is the point of buying PC2700 memory? If the memory is only running at 166 MHZ when its being run synchronous with the FSB, then why not use cheaper memory?

If someone could respond.


Thanks,
Robert

[StealthHawk]

DDR RAM is called double data rate because it can read data on the rising edge and falling edge of the clock cycle, unlike previous memory that could only do so once per cycle.

So, DDR333 is really running at 166MHz but it reads data twice, aka 333MHz effective. PC2700 never operates at 333MHz, it always operates at 166MHz. It does however, operate at 333MHz effective.