Increasing cpu voltage (on Via 266 chipset)

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I want to know about increased cpu core voltage.  Thank you for any
info.  Below is my situation.

-------

I have a somewhat old Syntax mobo based on a Via 266 chipset.  I use
a socket-A Duron 1.8GHz and it runs cool (under 50 degrees C at full
load).  SD-RAM timings are as fast as I can set them.

Unfortunately my mobo does not allow me to adjust the frequency
multiplier to the cpu.

All I can do is speed up the FSB (from 133 MHZ to no more than 140
MHz).  This slightly speeds up the processor.  The biggest
improvements from doing this seem to come from faster memory and
faster plugin cards.

-------

In addition, I can increase the cpu voltage by 25mV, 50 mV or 75mV.  
When I try one of these increased voltages it doesn't seem to do very
much.

My question is this:  

If all other things are equal then would the increased cpu voltage be
expected to improve cpu stability?  

OTOH would this also shorten cpu life appreciably?



Thank you.  
Jon


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crossposted to relevant groups:
  alt.comp.hardware.overclocking.amd
  uk.comp.homebuilt
  alt.comp.hardware
  comp.sys.ibm.pc.hardware.misc


Re: Increasing cpu voltage (on Via 266 chipset)

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Increasing the voltage makes transistors switch faster, which generally
allows the CPU to operate reliably at a higher frequency. Both greater
voltage and frequency increase the (electrical) power requirements; with the
same cooling arrangement that means an increase in operating temperature
which can, as I'm sure you know, cause unreliability.

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A higher operating temperature will shorten the CPU life; I am not sure what
effect the voltage alone has. In any case, it is likely that if the CPU is
working reliably, it will continue to do so for longer than it is useful.

While increasing the CPU voltage will generally allow the CPU to work at a
higher frequency, in your case - increasing the FSB frequency - you are
running pretty much everything at a higher frequency. If you increase the
CPU voltage and the CPU temperature remains reasonable but there is no
increase in the amount that you can overclock before you have instability
then it is likely that some other component is the weakest link.

Alex




Re: Increasing cpu voltage (on Via 266 chipset)

wrote:

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First of all, you'd be better off looking into an Athlon XP
or replacing the board, CPU, memory, etc, since any gains
with the Duron will be minor relative to newer parts.

Via 266 and Syntax alone don't tell us the details you may
need to o'c it.  First of all do you have bios settings or
jumpers for the voltage changes?  If so, is your Duron
multiplier-locked?  If so, your only recourse is raising the
FSB and memory bus... which you probably can't do much
because your board is only Via 266.  Sometimes they can hit
around 150MHz FSB, at which point the USB, IDE, and some PCI
cards like network adapters start crapping out.

Also Syntax boards are relatively low quality and can't
necessarily be expected to last as long in a higher current
(overclock) scenario.  

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How much time did you want to spend on this?  There are some
rather involved and risky (for someone starting out, not yet
knowing let alone doing some hacks ever before) things but
given the low potential for any kind of large benefit, I'm
inclined to think the effort isn't worth the return or risk.

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If you had some serious PCI bus bottleneck, yes it would
marginally help.  Usually it would help more to adjust the
PCI latency instead.  Google search for "PCI latency Tool",
it is more helpful on old Via chipsets than some, as Via had
a somewhat sluggish PCI bus during that era.




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What is your CPU's default voltage?

Supposing it's 1.6V, sure, going to only 1.675 isn't all
that much.  Certainly it's better than nothing though.


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Yes, if you were able to increase the CPU speed enough that
it needed a voltage increase.  At stock speed it should not
be needed at all.  Likewise it's probably not needed for the
minor overclock you've done.  Test with Prime95's Torture
Test, large in-place FFTs setting as that will often reveal
instability sooner than typical use.  It would need run with
no errors for several hours.


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Not from only 75mV, that's a rather minor increase.
More significant is how it effects your temps, and what
you're calling "full load".  Run prime95 with the highest
stable FSB you can use and the 75mV increase.  Monitor the
temps.  If it gets above 60C, you need a better heatsink,
more chassis airflow, faster 'sink fan, or to reduce your
overclock and voltage again.

Of course you should back up your data before trying this,
especially when overclocking the FSB since the resulting
higher PCI bus on Via 266 chipsets can corrupt HDD data.


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