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Re: Re: Help! Mathematica on my 500MHz outperforms my GHz machine!

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  • Subject: [mg22069] Re: [mg22012] Re: Help! Mathematica on my 500MHz outperforms my GHz machine!
  • From: "Mark Harder" <harderm at>
  • Date: Sat, 12 Feb 2000 04:04:28 -0500 (EST)
  • Sender: owner-wri-mathgroup at

Re. the following:
>Actually, the K7/Athlon uses the external bus/protocol of the DEC
>Alpha EV6, which is clocked at 200 MHz.  That interface "connects"
>with the motherboard chipset.  The motherboard chipset then "connects"
>independently with the RAM banks.  Current K7 boards use the AMD
>750/751 chipset which supports 100 MHz (PC100) SDRAM.  Upcoming boards
>will use the VIA KX133 chipset which has support for PC133 SDRAM.
>The 200 MHz EV6 processor bus allows plenty of "back-end" bandwidth
>and low latency for multiprocessing and such.
>Vijay Ram

....I read a recent article in PC Magazine about overclocking in Pentium
systems which stated that overclocking was accomplished by re-setting a
multiplier (in BIOS, or via MOBO jumpers) that determines CPU clock from the
system bus speed, i.e. to get a 500MHz CPU clock on a system with a 100MHz
system bus, set the multiplier to 5.
Now, if this is basically how Athlon CPU clock speeds are set, which bus
speed is used as the basis for multiplication, the DEC EV6 200MHz bus, or
the RAM & system bus (100 or 133 MHz)? If not, then just how are Athlon
chips clocked and overclocked?
    Suppose Athlon MOBOs determine CPU clock speed by multiplying the slower
system bus speed.  If one misunderstood this, and assumed that one could get
a 1GHZ Athlon by setting the multiplier to 5.0, one would only have a 500MHz
CPU! Could this be what happened to Jaczek?
    By the way, as a hardware ignoramus, I found the PC Mag article very
interesting.  Overclocking, according to it, is not something you should try
at home, unless you can afford to write off an Athlon or two to the learning
experience.  Sometimes overclocking requires higher CPU voltages, always it
generates more heat in the CPU.  If it isn't done just right, you can
shorten CPU life significantly.
harderm at

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