Processor FSB and Memory Question

[matt526]

I have a Pentium D 945 3.4 Ghz LGA775. 800Mhz FSB

and (4x)Samsung 512MB DDR2 PC2-4200 533MHZ

The CPU's FSB is 800Mhz and memory is 533Mhz so does this mean that the FSB of the CPU will only be 533 or as fast as the RAM. Should I upgrade to RAM to 800Mhz like PC2-6400?

Thanks

[matt526]

Any Help?

[harrycary]

Matching you FSB to your memory speed is best as you are probably encountering a bottleneck when your CPU tries reading/writing to your memory.

[matt526]

Ok I just upgraded from PC2 4200 533MHZ to PC2 6400 800MHZ
when I start up the computer and go into the bios it is telling me that the speed is only
667MHZ.
What would be causing this? could it be a voltage issue?

[hvymetal86]

check your motherboard's manual to make sure it can handle RAM running at 800MHZ. If not, you're probably stuck at 667, but its still better than 533...

[Broken]

Most motherboard will run you RAM in dual channel.
I.E. you memory would have an effective bandwidth of 533x2=1066FSB ( the speed of most C2D processors). The processor has a FSB of 800 so that's where the RAM is gonna default to.

Your new RAM being recognized as 667MHZ, I think that is PC 5300 right off the top of my head, is probably a result of the limitations of the Motherboard. Which isn't an issue if it's running in dual channel because it's gonna default to the FSB of 800 just like your old RAM when it's in dual channel.

Your "upgrade" unless you added more RAM was pretty much pointless.
The only thing that you might be able to do is run slightly tighter timings. But none the less, we are talking about a difference of 1 or 2 FPS in games.