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Confused about FSB and cpu:ram ratio

Last response: in Overclocking
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April 29, 2007 3:31:09 AM

I have an E6600, P5N32-E SLI board, and DDR2 800 ram. I'm not sure if I can run my ram and cpu at 1:1 cause when I set it for linked 1:1, it says my ram will be run at 1066mhz. I'm very new to the C2D overclocking but not to overclocking in general. I thought 1:1 was the best to run at but now I'm confused cause of the 1066 FSB. I see people refer to it as quad pumped but I have no clue what that means. Can I run my ram at 1:1 or will it really run at 1066 mhz?
April 29, 2007 4:03:21 AM

are you planning to oc your cpu? because if you aren't than you should have bought 533 (4*266) ram for 1:1. to have 1:1 ratio with your setup, you either going to have to oc your fsb to 400mhz (4*400=1600), or downclock ram to 533, or, obviously, match fsb:ram with the stable clock that you are able to achieve.
April 30, 2007 6:10:28 AM

Yeah I'm planning to OC but I don't understand why it says my ram is going to run at 1066 and not 533 when I put it at 1:1. My FSB is 266 so 266x2=533. Is this just an Asus thing or is it really going to run at 1066?
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April 30, 2007 6:23:11 AM

for a 1:1 cpu:ram ratio at E6600's default settings.

CPU FSB = 1066MHz (it's rated as 266MHz x 4 = 1066MHz)

Memory Frequency = 2x 266MHz (DDR = Double Data Rate. Therefore x2)

CPU Frequency = Multiplier x 266MHz = 9x 266MHz = 2.4GHz

Hope that make sense.


For yo to run your RAM at 1066MHz at stock settings, your RAM multiplier might be set at 4x.
April 30, 2007 6:28:10 AM

I understand all that but I still don't understand why my BIOS says my ram will run at 1066 if I try to do 1:1. My FSB is 266 therefore my ram should run at 533 on 1:1 not 1066 which is really really confusing me.
April 30, 2007 6:29:00 AM

What kind of RAM sticks are you running on? It's unlikely that your RAM are running on 1066MHz, unless you have really good quality RAM, as in PC2-8000 ratings and above, or you're overclocking the RAM.
April 30, 2007 6:38:00 AM

I'm using 6400's.
a b K Overclocking
a c 87 à CPUs
April 30, 2007 7:20:55 AM

I don't understand why it would claim that also. Double check the 1:1 ratio, and the 266MHz base speed setting. If that checks out as ok, then try booting into windows and run CPUz. If the bios claims that the ram will be running at 1066MHz, and CPUz says that its running at 533MHz, then maybe you have a bad/old bios? Are you sure that it says the ram will be at 1066? (1066 will be the effective FSB, not RAM speed.)
a b à CPUs
April 30, 2007 12:40:20 PM

I think the ration at stock 266MHZ is 4:6 to get 800Mhz. I have an asus but it doesn't give me a ration it just gives me all avaliable clock speeds at a given bus speed. Try unlinking it so you can manually change it. I can't remember how this is done but there are a few options like linked, unlinked, and another one that is something inbetween. To get 1:1 on DDR800 you will need 400MHZ fsb or if it is listing the "bus speed" you will need 1600MHz. You are correct the 1066 is quad pumped which is why it's 266x4=1066. The memory does not correspond to the 1066 at all only the 266. Some boards list the divider and some a multiplier. For DDR2 800 on stock bus speed you will need the 4:6 divider or x3 multiplier.
April 30, 2007 6:40:53 PM

I understand the clock speeds as described by Wiz83. What I don't understand is the relations ships between clock speed versus data transfer rates.

If my FSB is 266mhz (1066FSB) and my memory is 533mhz (1066 DDR2) the this is "1:1" However there is an obvious disparity in clock speed.

Technically a true 1:1 ratio would go something like 266mhz FSB and 266mhz DDR2 plus Dual channel memory (paired memory) would equal a 1066 FSB (I know this isn't correct)

Can someone please explain?
a b à CPUs
April 30, 2007 7:58:03 PM

I'm not sure what exactly your screen is showing because each motherboard shows it differently. The 1066MHZ does NOT make sense. The only thing I can think of it is giving you an "effective" rating if its running in dual channel. Because here is how the stock clocking works, this is probably a rehash anways.

Stock FSB = 266MHZ
Effective Bus speed = 1066 (this is quadpumped see. http://en.wikipedia.org/wiki/Quad-pumped )
Memory is DDR which means it does 2 transfers per clock cycle meaning:
266 x 2 = 533MHz. (1:1) you could put this to 4:6 which would give you 800MHz at the stock 266 FSB speed.
April 30, 2007 8:39:48 PM

Best results for gameing would be 1:1 with the highest speed you can get the RAM to run @ vrs RAM times....CPU can be kept stable by lowering it's mulitpyer.
I perfer to have highest OC while staying at stock voltages for everything.
April 30, 2007 10:26:33 PM

Ok, we are aiming in the right direction, but here is what I am seeing. My memory is Ballistix DDR2 1000 I have mildly over-clocked it to approx DDR@ 1066, each module is clocked at an actual 533mhz (1066/2=533mhz) My stock FSB on my E6600 is 1066 (quad pumped) for an actual clock of 266Mhz (1066/4=266).
What this means to me is that the data transfer rate is 1066Mhz equivilant. However the actual clock of the memory is literally 533Mhz and the FSB/northbridge chip is literally clocked at 266Mhz.
Can someone explain how data transfers across this bus? I am in dual channel mode (2x1GB memory sticks).

Does quad pumped mean that it can take two full RAM cycles of data from the memory in one clock of the FSB?
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