Memory newbie questions

What does the FSB have to do with memory bandwidth? Also does that correlate
to what kind of memory and can put on your board?

well you are best running the memory in sync with your fsb, so if you have a
400fsb cpu you'd be best getting ram, rated at 400fsb and running it at that
speed, also if you plan to overclock, you would be best even gettin higher
rated ram, so it will handle the higher speed.
"Ralph Dellinger" (Remove fake) wrote in message
news:U1i6c.7968$272.6459@lakeread03...
What does the FSB have to do with memory bandwidth? Also does that
correlate
to what kind of memory and can put on your board?

On Thu, 18 Mar 2004 09:15:34 -0500, "Ralph Dellinger"
(Remove fake) wrote:

What does the FSB have to do with memory bandwidth? Also does that correlate
to what kind of memory and can put on your board?


as i see it:

a faster FSB will allow data to flow quicker from memory to cpu,
increasing memory bandwidth. Intel's 800mhz is the market leader. AMD
follows with a 400mhz bus. Not surprisingly Intel has better memory
bandwidth. AMD is better at math if that's any consolation.

This situation evolved over time, so motherboards are backwards
compatible with the earlier FSB speeds which is why you see lots of
slower ram for sale still.

There's some new memory called DDR2 that's supposed to be the next
Intel thing later this year. But you'll need a yet to be released
motherboard for that.

I think it comes down to how much money you want to spend. Intel is
expensive, AMD is cheap. I'd go Intel for work and AMD for the home
user.

Ralph Dellinger wrote:
What does the FSB have to do with memory bandwidth? Also does that
correlate to what kind of memory and can put on your board?

Memory bandwidth is generally quoted and measured as the bandwidth between
the memory and the cpu. Since the CPU is connected to the Northbridge (via
the FSB), and the Northbridge has the memory controller on board and it
connects to the RAM (via the memory bus). As always, weakest link, so the
slowest of those two buses will be the limiting factor to bandwidth.

Memory bandwidth is not actually (completely) limited by FSB, as many of the
devices in your system can do bus mastering, or more specifically, DMA
transfers. This allows data transfers to and from RAM without intervention
of the CPU and therefore FSB. This is why you can see a gain in performance
with ram running faster than FSB (many other factors affect this - the
difference needs to be large enough to overcome the losses in converting
time bases)

Having said that, the new Athlon64s have the memory controller onboard,
there is NOT a FSB. The bus that connects the CPU to the Northbridge (which
no longer contains the memory controller) is the hypertransport link.

The memory you can fit to your board is not related to your FSB, but your
memory controller, which is likely in your chipset. There are chipsets that
support a faster memory bus than FSB.

Ben
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