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Old 09-18-08, 07:21 AM Thread Starter   #1
Scph9002
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question about multipel


Lets say i run 2 setups, one is maybe 7multi 450 bus an other wich is 9 multi but 400 buss wich both may or may not give 4ghz core speed, is there any downside whatsoever to run on lower multi?

And how does multipel works anyways ?

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Old 09-18-08, 07:59 AM   #2
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There is this equation for working out the speed of a processor :

FSB (Front side bus) X Multiplier = Core clock speed

So the higher the FSB, and the higher the multiplier, the faster the processor.
So for the first pc 450Mhz x 7 = 3.15Ghz (3150Mhz)
And the second 400Mhz x 9 = 3.6Ghz (3600Mhz)

It is just the ratio of the CPU internal clock rate against the data bus rate, so for a 7 x multiplier the CPU itself will complete 7 cycles, whereas the FSB would have only completed 1 cycle in the same time. FSB is how the pc communicates to other components on the motherboard.

So usually increasing the FSB on a lower multiplier (assuming same overall clock speed) will give better performance.

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Old 09-18-08, 08:52 AM Thread Starter   #3
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ah i see. Tried to boot up at 7 multipel and 533 buss for a nice 1:1 ratio with my mems, should be vastly superior to 9x400 as i had before? going from 3.6 to 3.7ghz core btw.

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Old 09-18-08, 09:50 AM   #4
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If you can hit 533, that will make hitting your RAM's rated 1066Mhz easy at 1:1 ratio. If your mobo doesn't like 533, you may need to lower the fsb, up the multiplier, and check what ratios are available in your BIOS.

F.ex: 355 Mhz FSB at 2:3 Ratio would be 1065Mhz (355*(3/2))*2, but only a 3.2GHz CPU clock. Just an example, your mileage may vary depending on what ratios you have available.
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Old 09-18-08, 10:45 AM   #5
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Higher FSB is not always better. There are timings to consider. Even if the FSB is going faster if it has to wait too many cycles then you negate the speed benefit, and have to run higher NB voltage.

Have a read. http://www.anandtech.com/mb/showdoc.aspx?i=3208&p=9

tRD is the timing that has a huge bearing on how effective your FSB speed is. Running 400 or 450 w/ a tight tRD may give you better performance than faster FSB speeds.

Try several settings and use Everest benchmark to make memory bandwidth comparisons. Try to get your RAM as tight as possible at each setting to ensure you can make accurate comparisons.

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Old 09-18-08, 04:17 PM Thread Starter   #6
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Quote:
Originally Posted by jason4207 View Post
Higher FSB is not always better. There are timings to consider. Even if the FSB is going faster if it has to wait too many cycles then you negate the speed benefit, and have to run higher NB voltage.

Have a read. http://www.anandtech.com/mb/showdoc.aspx?i=3208&p=9

tRD is the timing that has a huge bearing on how effective your FSB speed is. Running 400 or 450 w/ a tight tRD may give you better performance than faster FSB speeds.

Try several settings and use Everest benchmark to make memory bandwidth comparisons. Try to get your RAM as tight as possible at each setting to ensure you can make accurate comparisons.
got like 11.5k mb read/sec and 10.5mb copy/sec from 8k read and 8.5k copy or smth when going from 400-533 fsb :P

but didnt notice any big diference in 3dmark01... got like 57k instad of 55 :/

Edit:when you say trd do you mean the memory timings?

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Last edited by Scph9002; 09-18-08 at 04:51 PM.
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Old 09-18-08, 07:51 PM   #7
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The tRD setting in the BIOS is called Transaction Booster. If you haven't already, you really should check out the AnandTech article jason linked you to. It describes in detail how tRD affects memory performance, and the relationship between it and the FSB / NB (MCH) straps.

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