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I have a Gigabyte motherboard and cpu I inherited from my son when he bought a new gaming machine. I changed the BIOS from 8x to 6x multiplier as I don't need the speed and I'd rather it ran cooler and maybe more reliably. However, in system settings > details I don't think the reported speed changed. It is now saying

Intel® Core™2 Quad CPU Q9550 @ 2.83GHz × 4

My question is about how it determines the 2.83GHz, and could it be fooled by the manipulations of the BIOS?

Edit: More info.
The multiplier I referred to (and I probably used the wrong word) is the cpu clock ratio. Changing it to 6x, changes the CPU clock (as reported by the BIOS) to 2.00GHz (333MHz x6). It seems to me that the CPU temperatures are cooler now, since I changed it, so I think it is running slower - but still it is reported as 2.83GHz in Ubuntu

Edit: even more info

output from lshw -C cpu ...

  *-cpu:0                 
       description: CPU
       product: Intel(R) Core(TM)2 Quad CPU    Q9550  @ 2.83GHz
       vendor: Intel Corp.
       physical id: 4
       bus info: cpu@0
       version: 6.7.10
       serial: 0001-067A-0000-0000-0000-0000
       slot: Socket 775
       size: 2GHz
       capacity: 4GHz
       width: 64 bits
       clock: 333MHz
       capabilities: boot fpu fpu_exception wp vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx x86-64 constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 xsave lahf_lm tpr_shadow vnmi flexpriority cpufreq
       configuration: id=1
     *-logicalcpu:0
          description: Logical CPU
          physical id: 1.1
          width: 64 bits
          capabilities: logical
     *-logicalcpu:1
          description: Logical CPU
          physical id: 1.2
          width: 64 bits
          capabilities: logical
     *-logicalcpu:2
          description: Logical CPU
          physical id: 1.3
          width: 64 bits
          capabilities: logical
     *-logicalcpu:3
          description: Logical CPU
          physical id: 1.4
          width: 64 bits
          capabilities: logical
  *-cpu:1
       physical id: 1
       bus info: cpu@1
       version: 6.7.10
       serial: 0001-067A-0000-0000-0000-0000
       size: 2GHz
       capacity: 2GHz
       capabilities: vmx ht cpufreq
       configuration: id=1
     *-logicalcpu:0
          description: Logical CPU
          physical id: 1.1
          capabilities: logical
     *-logicalcpu:1
          description: Logical CPU
          physical id: 1.2
          capabilities: logical
     *-logicalcpu:2
          description: Logical CPU
          physical id: 1.3
          capabilities: logical
     *-logicalcpu:3
          description: Logical CPU
          physical id: 1.4
          capabilities: logical
  *-cpu:2
       physical id: 2
       bus info: cpu@2
       version: 6.7.10
       serial: 0001-067A-0000-0000-0000-0000
       size: 2GHz
       capacity: 2GHz
       capabilities: vmx ht cpufreq
       configuration: id=1
     *-logicalcpu:0
          description: Logical CPU
          physical id: 1.1
          capabilities: logical
     *-logicalcpu:1
          description: Logical CPU
          physical id: 1.2
          capabilities: logical
     *-logicalcpu:2
          description: Logical CPU
          physical id: 1.3
          capabilities: logical
     *-logicalcpu:3
          description: Logical CPU
          physical id: 1.4
          capabilities: logical
  *-cpu:3
       physical id: 3
       bus info: cpu@3
       version: 6.7.10
       serial: 0001-067A-0000-0000-0000-0000
       size: 2GHz
       capacity: 2GHz
       capabilities: vmx ht cpufreq
       configuration: id=1
     *-logicalcpu:0
          description: Logical CPU
          physical id: 1.1
          capabilities: logical
     *-logicalcpu:1
          description: Logical CPU
          physical id: 1.2
          capabilities: logical
     *-logicalcpu:2
          description: Logical CPU
          physical id: 1.3
          capabilities: logical
     *-logicalcpu:3
          description: Logical CPU
          physical id: 1.4
          capabilities: logical
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1  
And what is the speed you get in the bios? changing the multiplier just changes your FSB speed, which you need to also change. And bythe way the x 4 you see is the number of Cores the CPU has such as the Quad core name implies. –  Uri Herrera Jul 28 '12 at 23:31
    
The multiplier I referred to (and I probably used the wrong word) is the cpu clock ratio. Changing it to 6x, changes the CPU clock (as reported by the BIOS) to 2.00GHz (333MHz x6). It seems to me that the CPU temperatures are cooler now, since I changed it, so I think it is running slower - but still it is reported as 2.83GHz in Ubuntu. –  Jazz Jul 29 '12 at 0:01
    
Add that information to your question so it won't buried in comments. –  Uri Herrera Jul 29 '12 at 0:08

1 Answer 1

Temperature of the CPU is not a good method to determine clock speed. Temperature is determined more by what the CPU is doing rather than the raw clock speed so there's probably not much benefit to reducing the clock speed. Your reliability will be related more to power on cycles and power up time than anything else by the sound of it.

It's possible in any case for the clock multiplier to be overridden so you might need to look a little closer. Try:

sudo lshw -C cpu

to get a look at how the system thinks the cpu is clocking (and more)

share|improve this answer
    
By the way that's a heck of a machine for a cast-off... My main machine isn't even half of what you've upgraded to. –  fabricator4 Jul 29 '12 at 0:50
    
Yep, it's a rather nice machine :) –  Jazz Jul 29 '12 at 1:01
    
Updated the question with lshw output. The 2.83 number appears in the product name, but is the "size" figure (2GHz) the actual measured speed? –  Jazz Jul 29 '12 at 1:02
    
As for temperature in relation to clock speed, I've always been told overclocking will cause heat problems, and underclocking will save power and heat. –  Jazz Jul 29 '12 at 1:04

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