LinuxQuestions.org - Processor Question

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Processor Question - Athlon X2

I just replaced my Athlon 3500+ with an Athlon 3800+ X2.

Linux is showing the cpu MHz as 1000.000. Shouldn't this be 2000.00?

Quote:

x@debian:~$ cat /proc/cpuinfo
processor : 0
vendor_id : AuthenticAMD
cpu family : 15
model : 35
model name : AMD Athlon(tm) 64 X2 Dual Core Processor 3800+
stepping : 2
cpu MHz : 1000.000
cache size : 512 KB
physical id : 0
siblings : 2
core id : 0
cpu cores : 2
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 1
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt lm 3dnowext 3dnow pni lahf_lm cmp_legacy ts fid vid ttp
bogomips : 2012.06

processor : 1
vendor_id : AuthenticAMD
cpu family : 15
model : 35
model name : AMD Athlon(tm) 64 X2 Dual Core Processor 3800+
stepping : 2
cpu MHz : 1000.000
cache size : 512 KB
physical id : 0
siblings : 2
core id : 1
cpu cores : 2
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 1
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt lm 3dnowext 3dnow pni lahf_lm cmp_legacy ts fid vid ttp
bogomips : 2012.06

x@debian:~$

I could be mistaken, but the answer is Yes and No. As a dual core CPU, the CPU speed for the Athlon 3800 X2 is advertized as 2MHz, but as a dual core, you have 2 CPU's, and if each CPU is running at 1MHz, then 2*1MHz yields an effective speed of 2MHz. To use an analogy, it's a bit like comparing a $10 bill to two $5 bills -- in the latter case, the two bills have equal buying power to the single (larger) bill, and by the same token, for a given unit of time, two CPU's simultaneously operating at 1MHz have the same computing power as a single (faster) CPU running at 2MHz, at least in marketing-speak anyway.

I'll admit I don't know what the true results from /proc/cpuinfo should be for that CPU, but if they should be 2MHz, then could it be possible that your BIOS is underclocking the CPU? I'd kind of doubt that, seeing as how it is being recognized (correctly) as a 3800, but it's a possibility

A multi-core processor is not cumulative. If it saids it is clocked at 2 GHz, then both the cores will be clocked at 2 GHz. No it will not be 4 GHz and no processing power will not be increase.

You probably have Cool 'N Quiet enabled in the BIOS. If you turn it off, then you should see the the clock at 2 GHz. Though check if the settings in the BIOS is correct for your processor. If the processor was just been installed or its a new system build, the BIOS may sometimes under-clock.

Put the cpu under heavy load and check it again. I bet everything is fine.

Just a wild guess: could this be a kernel issue? If I understand correclty, the CPU was replaced but not the kernel - maybe it does not support dual cores?

Quote:

Originally Posted by jay73

Just a wild guess: could this be a kernel issue? If I understand correclty, the CPU was replaced but not the kernel - maybe the it does not support dual cores?

It shows two processors in the /proc/cpuinfo so he is running a SMP aware kernel already. To the OP as Electro has said you have Cool'N'Quiet enabled and the powernowd or one of the others daemon running so it slows down your processor and drops the voltage on the chip. My X2 3800 machine shows the same thing once you put the chip under load as lazlow mentions the speed and voltage jumps back to full levels.

Just as a side note, thanks for the input everyone. I personally hadn't realized the Cool'N'Quiet function affected clock speed. Thanks for the info