Project 850
A word of warning: If you remove the Athlon factory
casing you will lose your CPU warranty, so make sure you can live without it first.
The secret to getting a 500Mhz Athlon to go 850Mhz is
to make sure you don't really have a 500Mhz Athlon. While my Athlon says 500Mhz on the
case and it was sold as a 500Mhz unit, it is in fact an Athlon 650.
 
Taking apart the Athlon 500 shows that the core of the
CPU is really an Athlon 650. Note the K7650 printed on the top line of the core. This
tells you the CPU is a K7 650. The L2 cache is just as important as the CPU core when it
comes to overclocking the Athlon. My unit came with NEC 3.1ns units. This is good for
650Mhz (1000/3.1x2=650Mhz), which makes sense since this is really a 650Mhz CPU. So how do
you land a 650Mhz Athlon for the price of a 500? The easiest way is to go to K7 Core. They have a listing telling
which Athlons are the good ones. Then it's just a matter of calling around to local
vendors and asking if they have that unit available.
While an Athlon 500 that is really an Athlon 650 has no problem running at
650Mhz, it does takes some extra cooling to get it to run stable at 850Mhz. This is where
the Alpha P3125
came in. The Alpha P3125 was never meant to work with an Athlon. To make it fit I had to
rip the Athlon out of the case, remove the heat transfer plate and tap some new mounting
holes. Go here for the step by step. Looking back at it, I should have used an Alpha P7125 cooler
but there wasn't any available at the time.
The Athlon was overclocked using a PowerChip
PowerCharger. This Athlon overclocking device allowed me to adjust the Athlon
multiplier and voltage with a few flick of its DIP switches. Plugs right into the Athlon
goldfingers.
The big Alpha cooler does a great job keeping the Athlon within its
operating temp. As a matter of fact it does such a good job I'm able to run the system at
875Mhz. It's not 100% stable however. It runs Windows without problem but would lock up
after about 30 minutes of Quake 3.
To get 875Mhz requires the changing of the multiplier as well as the bus
speed. The Asus K7M offers this bus speed option, making 875Mhz usable. Notice that the L2
cache ratio is still set to 1/2. Most Athlons wouldn't be able to do this and it's the
reason why my Athlon is not 100% stable at 875Mhz. However, the system is 100% stable when
I set the L2 cache ratio to 2/5 but I found no speed increase between that and 850Mhz with
1/2 L2 setting.
Next Page: Cooling The Video Card
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