1:1 CPU:Memory Timings

[Nighthawk168]

Can someone please explain how to set 1:1 Memory timings. Or at least Check my Math

CPU = E6750 Core 2 Duo 2.66Ghz - 1333 Mhz FSB

CPU Timings: 8xMultipier Stock FSB=333MHz so, 333x8=2664


Memory = Corsair xMS2 PC-6400 DDR2-800 , so 800DDR2 divided by 2 = 400Mhz Memory Clock per DIMM?

In order to establish a 1:1 ratio between the CPU and Memory I would have to use the following:

CPU overclock by bumping FSB to 400Mhz so, 8x400= 3.2Ghz on CPU

Memory Remain at 400Mhz x 2 - DDR2-800 Stock speed.

Is this correct? and how does this affect the 1333 MHz FSB of the Core 2 Duo?

Thanks bro's

 

[MetaDFF]

Your math is correct. The lowest memory clock multiplier on Intel C2D motherboards is 1x, so setting your FSB to 400 MHz will automatically set your ram to run at 400 MHz (DDR2-800 stock speed).

I'm not sure what you mean by how it will affect the 1333 MHz FSB on the C2D. But basically you are running an effective 1600 MHz (Quad Pumped) FSB by setting the bus speed to 400 MHz.

 

[buzz12]

im also having a problem with this 1:1 ratio as well! since the new ddr3 are double date rate, then whats the use of anything higher than ddr3 1333 mhz (1333 divided by 2 = 667 actual speed!) i know that cpus are quad pumped and that high end cpus are now 1333 so (divided by 4 is 333), so to maintain the 1:1 cpu fsb with ram, you will have to overclock your cpu to 667!! and that is a number that i had never heared of anyone reaching!, or you could lower the bios ram settings to have the 1:1 ratio! which is a waste of the money spent on the ddr3s!
please help me to put an end to this confusion!

thanks in advanced

 

[Nighthawk168]

ok that helps a lot, is there an optimal setting to use ?

 

[myocardia]

Originally posted by: buzz12
im also having a problem with this 1:1 ratio as well! since the new ddr3 are double date rate, then whats the use of anything higher than ddr3 1333 mhz (1333 divided by 2 = 667 actual speed!) i know that cpus are quad pumped and that high end cpus are now 1333 so (divided by 4 is 333), so to maintain the 1:1 cpu fsb with ram, you will have to overclock your cpu to 667!! and that is a number that i had never heared of anyone reaching!, or you could lower the bios ram settings to have the 1:1 ratio! which is a waste of the money spent on the ddr3s!

Okay, I'll explain it a little differently, since you're new The first thing to point out is that Intel currently sells no CPU that has a stock FSB any higher than 333 Mhz, which the E6550, the E6750, and the E6850 all have, along with the QX6850.

The problem is that there are three different ways that motherboard manufacturers describe running your RAM at the same speed as your FSB*. Some call it 1:1 (the 1st # is the cpu, the 2nd the RAM), others just use the DDR speed, assuming you're running the FSB @ it's stock setting, while others call it 2x (on boards that use DDR2), because they assume most people don't realize that all DDR RAM actually runs at ½ the speed of it's DDR speed, if it's DDR, ¼ it's DDR2 speed, if it's DDR2, and 1/8 it's DDR3 speed, if it's DDR3. All three versions will have your RAM's actual speed @ 333 Mhz, as long as you aren't overclocking your cpu.

With your RAM speed set @ any of those descriptions above, your RAM speed is always identical to your FSB, period. If you want to raise your RAM speed, without overclocking your CPU, just use one of the higher multipliers.


*FSB= front side bus

 

[MetaDFF]

Originally posted by: Nighthawk168
ok that helps a lot, is there an optimal setting to use ?

I did a quick search for your RAM and it looks like they are specified at 5-5-5-12 timings for DDR2-800 operation.

As a starting point I suggest you set your RAM timings at 5-5-5-12 and the FSB to 400 MHz to see if your machine can POST. If your machine doesn't start up, your CPU probably needs more voltage (since we aren't overclocking the ram).

If your machine can post at 3.2 GHz with the above RAM timings and run stable at that speed (i.e. Orthos and Memtest), you can try to tighten them to 4-4-4-12.

Don't forget to lock the PCI/PCIE bus, you don't want to overclock that.

 

[buzz12]

myocardia thanks alot for explaning this front side bus issue, it really help me understand it.

 

[tno]

Woah woah Myocardia. DDR, DDR2 and DDR3 are evolutions of the same technology and that is that they allow data to both flow in and out simultaneously. But they are not doubled or tripled in any way. So where you say:
"DDR RAM actually runs at ½ the speed of it's DDR speed, if it's DDR, ¼ it's DDR2 speed, if it's DDR2, and 1/8 it's DDR3 speed, if it's DDR3"
you're wrong. DDR 400 memory and DDR2 400 memory both are rated at a FSB of 200, which is doubled (as in Double Data Rate). But technology enhancements allow the DDR2 memory to clock much higher than DDR memory. So we have DDR2 800 memory which runs again at the same speed and FSB (400) as DDR3 800. And again, DDR3 is simply a technological evolution that allows memory to run at speeds upto and beyond DDR3 1600. So from your quote above only that first part is true, and its true across all DDR technologies. What you are describing would be QDR and ODR (Quad Data Rate and Octo Data Rate).

Nighthawk,

To then answer the question posed. A 1:1 ratio means that your memory is operating with the same FSB as your CPU. So, if you're using an E6550, your FSB is 333 (or 1333 QDR, ignore that number though) and your memory is running at FSB 333 (667 DDR). Now, that is true regardless of whether you bought DDR2 1066 memory or DDR2 800 memory, and so on.

Most likely, your motherboard will run at a 1:1 ratio by default, so your FSB of 333 will apply to both your CPU and memory, out of the box. Now if it's not then it's running a different ratio and you can achieve 1:1 by other manipulating the ratio or by lowering the speed of your memory or by raising the speed of your FSB. Which method you use all depends on which method your motherboard employs. If you have any other questions feel free to PM or post. But remember, DDR/DDR2/DDR3 are all double data rate, that is their rated speed is achieved by multiplying the FSB by two; and not 1/4 or 1/8th of anything.

tno