FSB and DDR3 question (AM3)

helpimcrap

helpimcrap

helpimcrap

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i'm new to all this so apologies for asking obvious questions....

it's an AM3 with DDR3.

FSB at stock is 200, it's now at 230mhz. so its gone from 2.8ghz to about 3.2(?) ghz. what does the ram need to be at? is there a set figure?

on DDR1 boards you kept the ram at 200mhz using dividers - is it the same with DDR3 or do you keep it 1:1? :confused::o
 
Hi helpimcrap! :p

under normal conditions the motherboard is expecting to be run at 200MHz HT ref. Clock (fsb) and has a few different Memory-Multipliers to match-up with the different JEDEC standard memory speeds . . .

  • DDR3-1066 [1:2]
  • DDR3-1333 [3:10]
  • DDR3-1600 [1:4]
Once you adjust the HT ref. Clock upwards from the default 200MHz you just need to pick the correct Memory-Multiplier that keeps your sticks running within spec! . . . in some cases with the right adjustments (timings/volts) and careful testing you may be able to run the sticks stably beyond their rated speed! :) . . .

Working out the memory speed using the different multipliers is fairly straightforward, here’s the maths using different Memory-Multipliers across three different HT ref. Clock example speeds (200/225/250)
  • 200/1=200 x2=400MHz (DDR3-800) [1:2]
  • 200/3=66.66 x10=666MHz (DDR3-1333) [3:10]
  • 200/1=200 x4=800MHz (DDR3-1600) [1:4]
Now lets up the HT ref. Clock from 200MHz to 225MHz and see what happens
  • 225/1=225 x2=450MHz (DDR3-900) [1:2]
  • 225/3=75 x10=750Hz (DDR3-1500) [3:10]
  • 225/1=225 x4=900MHz (DDR3-1800) [1:4]
Now lets up the HT ref. Clock from 225MHz to 250MHz . . .
  • 250/1=250 x2=500MHz (DDR3-1000) [1:2]
  • 250/3=83.33 x10=833MHz (DDR3-1666) [3:10]
  • 250/1=250 x4=1000MHz (DDR3-2000) [1:4]
It's really that simple to work out as long as you perform the basic maths and just make sure the final speeds are within the scope of what your ram can handle! :cool:
 
cheers for reply - didn't realise there was a seperate forum for memory. :o

they are running at 240 mhz for now so about a 560mhz OC according to the BIOS/CPUZ etc. i'll have a go at figuring out dividers and see if they are ok or should i just leave them etc.

thanks for kinda explaining it to me. :)
 
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