Question about Multiplier on e6600

[Max2559]

Right... As mentioned in another post a have put a sonic tower on my conroe.

Was overclocking it and wanted to keep ram running at maximum 800Mhz.

Changed multiplier (default is 9) down to 8 and upped the fsb to 400. - Giving me (i thought a 3.2 Ghz overclock - 400x8 = 3200).

However when in windows easytune 5 and sandra are telling me its running at 3.6 Ghz.... what did i miss??

Not too displeased if it is actually running at 3.6... but as this wasnt what i intended id just like to know for future reference.

Cheers.

 

[Max2559]

Just checked it on cpu-z and its reporting 3.2 ghz... hmm... not sure whats going on here?

 

[The General]

EasyTune5 and Sandra are broken. CPU-Z reports the actual clockspeed.

 

[Max2559]

Right figured it out...

Sandra and easytune 5 are using the cpu's default multiplier... so taking a 400 msb... x 9 = 3.6

Interesting that they do that... you are right... cpu'z is correct.

 

[Ancalime]

I'm sorry this is off topic but I didn't want to start a new thread about it. Can anyone please tell me why you would lower the multiplier when you OC? What benefit do you gain? I thought it is a higher frequency that would increase heat and decrease stability.

Sorry newb here.

 

[Max2559]

Ok - basically you are right... to o/c you up the multiplier. However... just for a start thats impossible on a e6600 core2duo. it is only possible to lower the multiplier.

I did this as i wanted my DDR2 to run at its specified speed of 800Mhz.

If you up the FSB and dont change your RAM multiplier (a whole diferent thing to the CPU multiplier) then you will find your RAM speed changes too. If you push your FSB up... your RAM speed will go up too. - - This is one to watch out for...

Examples:

CPU multiplier = 9
FSB =367
RAM multiplier = 2.00

So 9x367 gives the CPU speed (3.3Ghz)
But the Ram will run at 2.00 x the FSB (367) = 734Mhz

So in this example the RAM is not performing as fast as it could... even though i have upped the FSB. However... if we try changing the RAM multiplier to try and squeeze out that last 66Mhz from the RAM look what happens:
Try Ram multiplier = 2.50

2.50 x 367 = 917.5Mhz (Now its running too fast and is in danger of damage)

So i tried the following combo~

Multiplier = 8
FSB = 400
Ram multiplier = 2

400 x 8 = 3.2 Ghz (Cpu speed)
and 2 x 400 = 800Mhz (Ram speed) as requested.

Yes ... the CPU has dropped 0.1 Ghz... there is always a slight trade off.

Might try getting it to:
Multiplier = 9
FSB = 400
Ram multiplier = 2

But im not sure i need or want to push it that hard. (3.6Ghz)

 

[Meithan]

When you say "RAM multiplier" do you just mean that your ram is DDR, or are you talking about the FSB:RAM ratio?

 

[Max2559]

FSB:RAM ratio - - Calling it RAM multiplier... as this is the number you multiply the FSB by to get the RAM speed . . (i thought)

I know its possible to select ratios on some Bios... on most boards infact! ... But my Gigabyte DS4 just has as i Posted 2.00, 2.50, 2.70 3.00, 3.50, 4.00 as options... Not really looking like ratios...

If there is a way of looking at the ratios on the DS4 more clearly id love to know... (Silly Bios make me press Ctrl F1 to adjust RAM timings and such).

Sorry if i used the incorrect terminology.... hope i got the point accross though.

 

[Meithan]

Remember that DDR *actual* clock speed is half the advertised speed. Your DDR2-800 RAM is designed to run at 400Mhz.

Also, FSB:RAM ratio is used to lower the speed of your RAM. To get RAM speed, you divide the FSB by your FSB:RAM ratio.
Example: if your FSB is 333Mhz and you have a FSB:RAM of 5:4, then the RAM speed will be 330 / (5/4) = 266Mhz.

If you want your DDR2-800 to run at full speed, you'll want to get your FSB as close to 400Mhz as possible while staying on a 1:1 FSB:RAM ratio.

I don't really know what "2.00, 2.50, 2.70 3.00, 3.50, 4.00" are in your BIOS settings. Anyone correct me if I'm wrong.

Can anyone please tell me why you would lower the multiplier when you OC? What benefit do you gain?

The performance of you CPU alone is determined by its clock speed rather than what multipliter it is being run at. So for instance having it running at 200Mhz x 10 or at 250Mhz x 8 will both correspond to a 2.0Ghz clock speed, and produce similar CPU performance. However, the higher FSB means the CPU will be communicating with everything else on your computer much faster. So even if you lowered the multiplier, you'd still get an overall performance gain.

 

[idiotec]

Remember that DDR *actual* clock speed is half the advertised speed. Your DDR2-800 RAM is designed to run at 400Mhz.

Also, FSB:RAM ratio is used to lower the speed of your RAM. To get RAM speed, you divide the FSB by your FSB:RAM ratio.
Example: if your FSB is 333Mhz and you have a FSB:RAM of 5:4, then the RAM speed will be 330 / (5/4) = 266Mhz.

If you want your DDR2-800 to run at full speed, you'll want to get your FSB as close to 400Mhz as possible while staying on a 1:1 FSB:RAM ratio.

I don't really know what "2.00, 2.50, 2.70 3.00, 3.50, 4.00" are in your BIOS settings. Anyone correct me if I'm wrong.

While historically memory dividers were used to lower the RAM speed in relation to the FSB, this is not often the case with DDR2-Intel systems. Primarily because DDR2 speeds are faster than Intels FSB. On current 965 boards, there are actually NO options below 1:1. That means that the lowest you can run the RAM is equal to the FSB, however, you can run the RAM faster than the FSB.

The 2.00, 2.50, etc, ARE the memory dividers. 2.00 represents 1:1 all the way up to 4.00 which is 1:2 (FSB:RAM). I will agree that it is kind of a crappy way Gigabyte has chose to show them in the BIOS, but they work the same way so not a big deal.