My motherboard FSB is 333MHz (quad pumped to 1333MHz). It only supports DDR2. If I want my memory to operate synchronously, is DDR2-667 the only option that I can purchase?

If I buy DDR2-800, the FSB will be 333MHz and the memory bus will be at 400MHz?
If I buy DDR2-1066, the FSB will be 333MHz and the memory bus will be at 533MHz?

So, it seems like any faster RAM means it will operate asynchronously with the FSB. What's strange is that I don't see any option to change the memory divider in BIOS settings.

Thanks for any help.

any ram abv 533 will work fine in your system, the ratio doesnt have to be 1:integer. it can be 2:3 ect.

if you want 1:1 you could get 677, or un attach the ratio and overclock the FSB to 400.

Memory Divider Options are usually in the BIOS - sometimes hidden a couple layers deep. What motherboard/BIOS revision do you have?
Usually there is no problem with Asyc memory/FSB operations.
If you're OC'ing the 1:1 FSB/RAM ratio is usually preferred - and that would mean that DDR2-800 RAM would be running at an effective DDR2-667 speed at the stock CPU speed.

>>>that would mean that DDR2-800 RAM would be running at an effective DDR2-667 speed at the stock CPU speed.

Does it mean DDR2-800 will be running at 667 if I don't OC my FSB to 400?

If you "lock" your FSB/RAM ratio at 1:1 through BIOS options your RAM with "run" in sync along with your CPU. CPU 333 RAM 667 - - CPU 350 RAM 700 - - CPU 380 RAM 740 - - CPU 400 RAM 800 - - CPU 425 RAM 850 and so on.

My mobo is Gigabyte EP35-DS3.

So, if the FSB/RAM ratio is locked at 1:1, no matter how fast the RAM I install, it will run at 667 if FSB is set at 333?

Where can I "unlock" the FSB/RAM ratio? I can't find it in my BIOS settings.

Thanks

press ctrl+f1 when in bios, it opens up the memory settings (or at least for the ds3l it does)

am I right in saying that there doesn't seem to be much evidence that running memory in sync with fsb produces a decent benefit?

look, if you install 800mhz ram into a machine with a 333mhz FSB, they would both run at there specified speed. the chipset woudl calculate a ratio for you. wehny uo overclcok the ram and Fsb both Overclock in the ratio as specified.

however if you told your motherboard to think that DDR 800 was 677mhz, then you would have a 1:1 ratio and it would allow you to overclock you RAM upto and above 800.

its kind of hard to explain but just trust that most DDR2 (677 throguh to 1066) will work in your system.

kind of hope this helps

well the thing is that running it out of sync (ie faster) doesn't really give any benefits, so 1:1 is preferred for overclocking because it is easier for the ram to keep up with the higher fsb

Correct - although the major benefit maybe be overall system stability. There seem to be certain "sweet spots configs" where MB/FSB/RAM seem to be more stable than in some other configurations. Variables are MB make and model, CPU, RAM make and model and voltages.