Silly question about multi and FSB

SlyReaper

SlyReaper

SlyReaper

Soldato
Joined
26 Apr 2008
Posts
6,653
Location
Bristol, Old Blighty
Why can I quite happily run my E2160 at 360x9 = 3.24GHz, but not 400x8 = 3.2GHz? I'm certain my board should be able to do that FSB.
 
My Q6600 won't stay stable at 1600 fsb with any multiplier. be it 6x (2.4ghz) or 7 or 8.

But it will be stable up to around 1450 ish fsb. I guess that some cpu's can't run certain fsb? I don't know I am just as confused as you.
 
SlyReaper said:
Why can I quite happily run my E2160 at 360x9 = 3.24GHz, but not 400x8 = 3.2GHz?
Click to expand...

Hey SlyReaper,

I would say the simple answer is that your overclocking your Northbridge too much and something is crapping out. What you may not realise is that by lowering the default multiplier on your CPU you are actually raising the multi on something called the NBCC (NorthBridge Core Clock)

The NBCC frequency is worked out using the following formula

  • [Native] Multi divided by [Set] Multi = A
  • [Set] FSB = B
  • A x B = NBCC MHz
Intel® Pentium® Processor for Desktop E2160 (9x200)

9 x 360 = 3240MHz
NBCC = 360MHz

9 x 400 = 3600MHz
NBCC = 400MHz

8 x 400 = 3200MHz
NBCC = 450MHz

To help keep the Northbridge stable at higher frequencies it needs more volts in much the same way as your CPU normally clocks better if you give it more volts!
 
Hey no_1_dave,

I know what you mean, sometimes these things make no sense until you really look into it!

The difference between your chip and SlyReaper's chip is yours is a native 266MHz-FSB and his is a native 200MHz-FSB

This corresponds to how the motherboard sets up the Northbridge straps, 266-Strap for yours and 200-Strap for his. Of course we all expect a decent motherboard to adjust itself depending on what FSB it's running but I have reason to believe that is not always the case! :(

I think that SlyReaper's 200-Strap chip will need some expert user intervention in the BIOS to make sure it has a chance to overclock well because the BIOS will have set some internal timings (tRD etc) thinking the machine is gonna be running at 200MHz-FSB (800MHz-System Bus) which unless manually changed (i.e relaxed) will really not help when trying to run some fast frequencies through the Northbridge! :eek:

I also just noticed that SlyReaper is running DDR3 which again puts a lot of added strain on the Northbridge Chip . . .

GIGABYTE GA-P35C-DS3R (DDR2/DDR3)


So that's *Three* good reasons why SlyReaper is having problems

  • Overclocking the NBCC by selecting lower CPU Multi
  • Overclocking the 200-Strap/tRD by raising the FSB
  • Overloading the Northbridge (MCH) by running uBer fast DDR3
So the component that SlyReaper is really kicking the **** out of is not the Intel® Pentium™E2160 but more likely the Intel® P35 Express Chipset ;)


Intel® P35 Express . . . think of it as another Processor!
 
Sorry, may be a silly question (this does seem like the thread to ask it in though :D) but would you see any performance difference between an E2160 at 360x9 and one at 400x8? Would the higher FSB be better?
 
jeffmango said:
would you see any performance difference between an E2160 at 360x9 and one at 400x8? Would the higher FSB be better?
Click to expand...

Intel® Pentium® Processor E2160 (9x200) 1.8GHz

9 x 360 = 3240MHz
9/9 = 1 x 360MHz = 360MHz NBCC

8 x 400 = 3200MHz
9/8 = 1.125 x 400MHz = 450MHz NBCC

I reckon an extra 90MHz on the NBCC sounds faster to me! ;)
 
Overall system performance is not about CPU MHz alone, it's about a balance between all the other important factors like NBBC MHz, Memory MHz and Northbridge timings (tRD).

You must understand all the factors involved and do your own testing to confirm! :)
 
SlyReaper for testing purposes can you please try:

9 x 400 - Out to lunch!

8 x 355

7 x 311

6 x 266

All equal 400MHz NBCC on your Intel® Pentium® E2160
 
You must log in or register to reply here.
Back
Top Bottom