Confused by all the numbers :s

[wahoyaho]

So, say DDR2-6400 is rated at 800MHz, that means the bus clock is at 400 and the memory clock is at 200? Whereas when it's DDR-3200, it's rated at 400MHz and the bus and memory clock are both at 200?

So now enter the C2Ds, so the E6300 has a FSB of 1066 but it's quad pumped so it's actually 266MHz with a multiplier of 7, meaning you'd need a DDR2-4300 to match the cpu 1:1 since DDR2-4300 is rated at 537mhz, so that's an actual bus clock of 266MHz?

What about the AMD X2s? Like the 5200+ has a HT of 2000MHz, how did they get that number? Is the FSB still 200 with a 13x multiplier? So you'd need DDR2-3200 to match it?

 

[orion23]

I don't understand the 1st or last!

But the C2D math is right, except for the DDR2 4300.

DDR2-4200 is 533mhz and that's the "requirement".

Anything faster is meant for overclocking either the RAM alone, or the FSB

 

[bryanW1995]

my head hurts.

 

[n7]

Originally posted by: wahoyaho
So, say DDR2-6400 is rated at 800MHz, that means the bus clock is at 400 and the memory clock is at 200? Whereas when it's DDR-3200, it's rated at 400MHz and the bus and memory clock are both at 200?

So now enter the C2Ds, so the E6300 has a FSB of 1066 but it's quad pumped so it's actually 266MHz with a multiplier of 7, meaning you'd need a DDR2-4300 to match the cpu 1:1 since DDR2-4300 is rated at 537mhz, so that's an actual bus clock of 266MHz?

What about the AMD X2s? Like the 5200+ has a HT of 2000MHz, how did they get that number? Is the FSB still 200 with a 13x multiplier? So you'd need DDR2-3200 to match it?

You've got it.

But due to overclocking & RAM being cheap, many people get faster DDR2-667, etc., since running faster RAM = more bandwidth = faster, which never hurts

 

[JustaGeek]

The motherboard uses so called "memory dividers" to increase the speed of memory bus.

If you go 1:1 then yes, 266MHz FSB will give you 533MHz memory frequency (2x = DDR; Double Data Rate).

Using the memory divider, e.g. my FSB speed is 325MHz x 16/13 divider = 400MHz x 2 = 800MHz memory speed.

Everything revolves around the speed of the Front Side Bus - the rest is just the Multipliers and Dividers.

 

[Shimmishim]

ddr2-6400 = 800 mhz mem

the FSB and MEM are usually correlated by some sort of divider

the most common are 1:1, 4:5, 2:3 which are found on intel chipset boards (not too sure about amd as its been a while for me).

when your fsb is running 400 and your mem is running 800 (400x2)then you are 1:1 and your mem is running at ddr2-6400.

4:5 would be fsb 400 and mem at 500 (500*2) or ddr2-8000
2:3 would be fsb 400 and mem at 600 (600*2)or ddr2-9600

there are "negative" dividers which make your mem run slower than your fsb but you usually don't see it on intel chipset boards unless you're running on the 1333 strap (such as the intel bad axe 2 where you can select your strap).

 

[JustaGeek]

DDR2 800, or PC6400 = 800MHz mem

Memory bus is 400MHz, assuming 1:1 divider with the FSB running at 400MHz.

But with the FSB=325MHz and the memory divider 16/13, the memory bus will still be 400MHz, for the memory speed of 800MHz (Double Data Rate).

 

[Shimmishim]

Originally posted by: JustaGeek
DDR2 800, or PC6400 = 800MHz mem

Memory bus is 400MHz, assuming 1:1 divider with the FSB running at 400MHz.

But with the FSB=325MHz and the memory divider 16/13, the memory bus will still be 400MHz, for the memory speed of 800MHz (Double Data Rate).

yeah i guess that's a better way to put it.

 

[geokilla]

Not sure if this question will help the OP or not, but what is so good about running 1:1 anyways. Can't I run something like 4:3 instead so I can run my say for example, DDR2 at 800Mhz at what it's rated for instead of leaving it at 533Mhz so I can get a faster memory speed while keeping the FSB at 266?

 

[JustaGeek]

To run memory with 4:3 multiplier your FSB would have to be 300MHz for 800MHz memory speed.

300 x 4 / 3 = 400 --> 400 x 2 = 800 MHz

For FSB at 266MHz your memory divider will have be 3:2 in order to get 800 MHz memory speed. And yes, the memory will generally be faster, or rather will have greater bandwidth than 533MHz run 1:1.

266 x 3 / 2 = 400 --> 400 x 2 = 800 MHz.

 

[RichUK]

nvm

 

[Shimmishim]

Originally posted by: geokilla
Not sure if this question will help the OP or not, but what is so good about running 1:1 anyways. Can't I run something like 4:3 instead so I can run my say for example, DDR2 at 800Mhz at what it's rated for instead of leaving it at 533Mhz so I can get a faster memory speed while keeping the FSB at 266?

yes.

that is the purpose of dividers

as the person below you posted, you can run your fsb at 266 and run your mem at 400 by using a 2:3 divider.

 

[Cheex]

Originally posted by: bryanW1995
my head hurts.

my head hurts.

 

[coldpower27]

Originally posted by: wahoyaho
So, say DDR2-6400 is rated at 800MHz, that means the bus clock is at 400 and the memory clock is at 200? Whereas when it's DDR-3200, it's rated at 400MHz and the bus and memory clock are both at 200?

So now enter the C2Ds, so the E6300 has a FSB of 1066 but it's quad pumped so it's actually 266MHz with a multiplier of 7, meaning you'd need a DDR2-4300 to match the cpu 1:1 since DDR2-4300 is rated at 537mhz, so that's an actual bus clock of 266MHz?

What about the AMD X2s? Like the 5200+ has a HT of 2000MHz, how did they get that number? Is the FSB still 200 with a 13x multiplier? So you'd need DDR2-3200 to match it?

Athlon 64x2 work differently, since they don't have FSB they just take advantage of whatever memory speed you have.

From what I recall they use dividers to get your memory speed.

Say you have a 6000+ X2, 3000/9 = 333.3 which would work out well for DDR2-667, if I recall correctly. Unfortunately, due to the use of Integer only values, for DDR2 processors not all based clockspeeds will result in a match with the memory speed.

2800/7 = 400 which is great for DDR2-800. 2800/9 is closest though for DDR2-667 as that allows 311 which is DDR2-622.