FSB issue

Soldato
Joined
19 Jun 2009
Posts
6,392
Location
London
Hey guys/girls, i've had this problem for quite a while now and I'm really hoping somebody can help me get to the bottom of this. If I set my FSB to anything above 300 (e.g. 400 X 7.0 multiplier) my system would randomly reboot itself. However if I use 300 x 10.0 multiplier it is completely stable.

Asus P5Q Deluxe
Q6700 with G0 stepping - 3GHz - 1.34v
NB voltage = 1.44 paired
8GB DDR2 OCZ Gold 8500 @ 960MHz - 5-6-6-18 - 2.1V

I'd like to get the ram at 800MHz and FSB at 400 eventually for a 1:1 ratio; is this what I should be aiming at or is running 5:8 fine?

Any help would be appreciated.

Thanks
 
Quite simple I would say. Your CPU has a FSB wall, or that you need to set more voltage to allow a higher FSB. There is less energy deficit with a mulit increase than with a FSB increase. Both will require additional voltage - normally auto would be fine for multi and a modest overclock.

You can test that out by the way. Drop your multi to 6 and see what is the max you can get. Use Setfsb to increase your FSB in OS in small steps of 4 or 5 FSB at a time. You will find your FSB wall.

As to what is causing that FSB wall, well it could be ram, the motherboard or even the CPU it self. To many factors to nail down based on the information you have provided.
 
  • Intel® Core™2 Quad Q6700
  • Asus P5Q Deluxe
  • 8GB DDR2 OCZ Gold 8500 @ 960MHz - 5-6-6-18 - 2.1V
  • NB voltage = 1.44 paired
If I set my FSB to anything above 300 (e.g. 400 X 7.0 multiplier) my system would randomly reboot itself. However if I use 300 x 10.0 multiplier it is completely stable.
Hello nayan89,

the simple answer is through a combination of the chip you are using, fours sticks of RAM and manually setting your vNB the Intel® P45 northbridge chip (NBcc) is spazzing out! :D

If you want to just keep things simple for the moment and get to a safe plateu I would suggest you reset the BIOS so the board sets things back to [Auto] and for a simple 3.30GHz Overclock . . . you should be able to achieve this with "minimal" effort just by adjust the FSB from 266MHz up to 333MHz, setting the memory frequency to approx DDR2-1066 and then simple adding vCore if the [Auto] setting doesn't give the chip enough juice!

To break this clock up into two stages I would try for 3.30GHz with the memory at DDR2-800 leaving you to just work on the vCore . . . then once the CPU clock is sorted I would then switch up the ram from DDR2-800 to DDR2-1066

Intel® Core™2 Quad Q6700 @3.3GHz
  • 333 x 10 = 3330MHz
  • 400MHz (DDR2-800) [5:6]
Intel® Core™2 Quad Q6700 @3.3GHz
  • 333 x 10 = 3330MHz
  • 533MHz (DDR2-1066) [5:8]
Ok so that's the easiest route forward for you atm . . . if you get that cracked then perhaps we can push further . . .





[Advanced User Info]

Nortbridge Core Clock (NBcc)

Now the reason you were running into problems when messing with the CPU Multi and cranking the FSB is due to a little known subject . . . the NBcc

The NBcc is the core clock of the nortbridge and is the thing that generates the FSB . . . when you changed the "Native" multiplier downwards you actually increase the NBcc . . . not many people know or understand this but for the simplest clocks leave the CPU multi at its "Native" setting . . .

The mathmatics for working out your NBcc speed is as follows

  • [Native] CPU Multiplier Divided by [Set] CPU Multiplier Multiplied by [FSB]
For the easy clock suggested above the NBcc maths is easy
10/10x333= 333MHz

Now look what happens when you manually lower the CPU multipler and crack the FSB right up as you mentioned in the O.P
10/7x400=571MHz

Even though you will only see 400MHz-FSB displayed in CPU-z the NBcc will be running at 571MHz which along with a full bank of RAMs and the vNB set to manual will flop . . .

If you don't understand the NBcc maths then leave the CPU multiplier at its native . . . if anyone doesn't understand the NBcc maths then do not advise people to lower there CPU multiplier until you understand the impact this has on the Northbridge! ;)

Sorry for the long post but hopefully you and others may find this info useful! :cool:
 
Thank you so much Big Wayne for your post, and to 1Day also. I find it easier to understand what is going on now. As for now it seems 960mhz ram and 300 x 10.0 for cpu is stable and has passed 8 hours of stress testing (prime 95, intel burn test, memtest, super pi). I will try pushing it to 1066mhz with your recommendations sometime soon and will keep you updated should I do so.

Thank you once again :)
 
Following Big Wayne's recommendations I have successfully managed to get the following overclock stable:

333FSB x 10.0 multiplier = 3.3GHZ
CPU Voltage = 1.34V
NB Voltage = 1.46
DRAM/FSB Ratio = 5:8

I've gone back to 4GB DDR2 Dual Channel
5-5-5-18 @ 2.1V 1066MHZ

I've run prime95 for 10 hours and the max temps I reached were 67/66/65/65. Intel burn test after 10 rounds was 69/68/67/67.

Idle temps are 37/36/34/34

Once again I'd like to thank Big Wayne for the help and 1Day for his input aswell. I think I could probably get to 3.4GHz but 3.33ghz is enough for me for now :D

merry xmas o/
 
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