Archived from groups: alt.comp.hardware.overclocking.amd (
More info?)
Dave wrote:
> Knuelle wrote:
>> YanquiDawg wrote:
>>>> Can Somebody tell me why Athlon 64 3400+ is only getting a clock
>>>> speed of 798mhz? And what do I need to overclock and check temps?
>>>
>>> What is the FSB set to?Should be 200.
>
>> i guess its just a mathematical problem that he doesnt get exactly
>> 800?
>
> No, it just means his clock generator is not at the exact frequency
> and is nothing to worry about. There is usually some variation,
> however slight.
It should be mentioned that "clock generator" in this context is a bit
ambiguous. You have the base clock that is multiplied for the FSB clock (for
example 1MHz), and then you also have the ~1.180 MHz realtime clock. Both
sources will have drift and inherent inaccuracy, and since the method used
is effectively "how many cycles per RTC event", you're effectively measuring
the frequency ratio of the two sources (by dividing out the CPU multiplier).
There's also the ACPI timer (~3.6MHz?) which is another independent source
that is sometimes used. In addition to this you have crystals on the video
card (your 85Hz may not be 85Hz
), your LAN card (which are usually the
most accurate source in a computer, especially on the gbps cards), and sound
card. All running nicely out of sync, which makes measuring the TRUE
frequency of the CPU to more than a couple significant figures quite a
challenge.
--
Michael Brown
www.emboss.co.nz : OOS/RSI software and more
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