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Front Side Bus

Last response: in CPUs
June 7, 2008 3:21:01 PM

Am I understanding this correctly?( I am a newbie )

Front side bus is determined by the CPU and limited by the MOBO?

1) So even though I have an (Intel Core Duo E6600 2.4Ghz with a FSB of 1066) I would be limited if I
decided to go with say a (Quad Core with a FSB of 1333) because my MOBO has a max FSB of 1066?
So the MOBO and the CPU determin the FSB????

Also in trying to understand the math. The above 2.4Ghz is actually running mem at 1600Mhz
because my FSB is 1066 and my mem is only PC5300 667mhz,
base mem speed is 333Mhz though since the FSB is 1066Mhz, max is 266.7mhz and since this
processor is limited in multiplier at x6 ( darn Dell motherboard 680i nvidia chip set. )
I am actually only getting 266.7 x 6 = 1600 Mhz???

2) So if i ?upgraded? to pc6400 800Mhz mem the base speed would be 400Mhz and 400 x 6= 2400 but that would be wasted since the FSB is only 1066 and I would bottle neck...?

If I may.. one last newbie question on mem if it says 4,4,4,12 on the Pc6400 800Mhz mem what do those
numbers actually mean:
Cas# latency/Ras# to Cas#/Ras# precharge/ tRC

Thank you for being patient.. :D 

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June 7, 2008 3:58:07 PM

Your motherboard uses dividers to select the memory speed. Use cpuid (a free download) to determine the actual speed of your cpu and memory when overclocking. Lower numbers for memory timing (4,4,4,12) are faster, but may require a voltage increase when overclocked to prevent windows bluescreens. 266 is the base fsb for your cpu. 266.67 x 4 gives you the 1066 figure. 266 x the locked multiplier of the cpu will give you the base speed of 2400 hertz. For the q6600, the multiplier is 9. 9 x 266.67 = 2400. I'm no expert on what the tras, ras to cas, etc mean. You'll have to google it to find out more. There is one website dedicated to bios terms, but I haven't used it in awhile and don't remember the name. As far as limits, overclocking depends on the cpu capabilities, voltage settings in your bios, available memory dividers, the quality of your memory, power supply rating, heatsink cooling, etc.
June 7, 2008 4:54:26 PM

The FSB is determined by the base MHz which, in your case, is 266 X 4 = 1066MHz.
The cpu speed is determined by the cpu multiplier which should be 9 and why your cpus speed is 2400MHz. It says your cpu is running at 1600MHz because Stepspeed is on, it causes the cpu to run at the lowest multiplier (6).
The timings on the RAM is simply how fast it responds. The lower the better. Read more about it on wikipedia.
You should set your memory divider at 1:1 in your BIOS. New memory isn't necessary unless you overclock at put your base speed over 333MHz.
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June 7, 2008 4:54:57 PM

Stupid browser! Another double post.
June 7, 2008 7:45:29 PM

thank you, i changed the stepspeed and got the multiplier back to the x9 that it is ment to be instead of the x6. WOuld it be worth me going to Pc6400 the 800Mhz mem with this processor and motherboard? At this time I do not want to try overclocking.
June 7, 2008 7:56:28 PM

You should leave on stepspeed, it changes the multi back to 9 under load. It saves bit of power and makes the cpu run cooler. Forgot to add that earlier, soz. Unless you want more RAM, theres no reason if you don't OC. If you have Vista 2GB+ is recommended, made a world of difference with mine.
June 7, 2008 9:15:54 PM

sw: CPU speed/FSB speed and memory bus speed are independent. However, all data to/from the RAM has to pass through the FSB, as follows:
RAM <-> memory bus <-> north bridge <-> FSB <-> CPU
What that means is that it doesn't really help to increase the memory bus datarate higher than the FSB datarate or vice versa. To match the datarates, just take the FSB datarate (1066MHz for example) and divide by 2 to get the matching memory module speed (assuming the memory bus is running in dual-channel mode). Thus, for a 1066MHz FSB, run your RAM modules in dual-channel mode at DDR2-533 speed.
June 7, 2008 11:09:29 PM

so what if I upgraded to a Q6600 and overclocked, and went with mushkin DDR2 6400 800Mhz ( 2 x 2Gb ) 5-4-4-12 at 1.8v mem. what would I see?
Nothing due to the 1066Mhz FSB???
June 7, 2008 11:24:26 PM

Unless Dell has any BIOS options for you to raise your FSB (which I doubt, since most all OEM mobos don't allow overclocking) - your system would just run the DDR2 6400 at the slower (533) speed. So, it would be a waste of money to replace your RAM if this is the case.

Your mobo is set to run with 533 RAM, and unless you have BIOS options to raise your FSB and change your memory divider, then adding faster memory won't help.

With an OEM system, your overclocking is limited by your motherboard's BIOS (and it's lack of overclocking abilities), not the 1066MHz CPU.