Overclocking the PIII 500E
Ok, the system is set back to 166Mhz on the graphics card,
but still has the RAM at 128MB. I've changed the BIOS to 100Mhz
on the FSB and have it showing 1.6v on the core voltage. The
clock multiplier has been set to 5.0 to match the 500E. It's
time to fire it up and get some benchmarks. The system now produces
a 42.4 at 1024x768. This is a only 1.3fps increase from the
system with the Celeron set at 464Mhz, but if we look at the
800x600 video mode we see that the fps is now at 60.7 instead
of 47.1. That's a 13fps (28%) increase. Setting the graphics
card to 178Mhz gives us 45.6fps at 1024x768, an additional 3fps
from the 166Mhz setting. The 800x600 video mode is now at 63.4fps,
The next step up on the FSB available on the BH6 is 103Mhz
(turbo enabled on the 100Mhz FSB), but let's move on to the
next step, 112Mhz. There are other things besides whether a
CPU is overclockable that can stop you from overclocking your
CPU higher than its default rate. The external clock setting
(FSB) in the BH6 BIOS shows beside the number a ratio in parentheses.
This ratio is the FSB to PCI bus ratio. At 100Mhz the ratio
is 1/3 which puts the PCI bus at 33Mhz, right where it should
be. The 1/3 and 1/2 (1/2 is used by the 66Mhz buses) PCI ratios
are the only two available in the BH6. When we move to the 112Mhz
FSB setting the ratio is at 1/3 which gives us 37.3Mhz on the
PCI bus. This is not too bad and shouldn't cause any problems
with most PCI cards.
The first time I tried to boot at this speed (112 x 5.0 = 560Mhz),
the PC locked up trying to bring up Windows 98. After pressing
the reset button, the system successfully booted into Windows
98. Running the benchmarks at 166Mhz and 178Mhz on the graphics
card at 1024x768 yielded 42.4 and 45.6 respectively. At 800x600
62.6 and 66.2 at the 166Mhz and 178Mhz graphics card settings
So why did Windows 98 give me some trouble the first time I
tried to reboot. If you've been reading real closely, you may
have noticed that I have not mentioned changing the AGP clock
ratio during any of the BIOS settings for overclocking the CPU.
At 66Mhz the AGP clock is set to use a 1/1 ratio with the FSB
which puts the AGP bus at 66Mhz. When I set the FSB to 100Mhz
for the Celeron 300A and 500E CPUs, I didn't change the AGP
clock ratio setting. This put the AGP bus at 100Mhz, well over
the standard 66Mhz setting. At this bus speed the Voodoo3 did
not roll over and die, it just kept on running. However, when
I set the FSB to 112Mhz and left the AGP ratio at 1/1, the Voodoo3
3000 started to object a little to being stressed at that level.
This was also evident by the scolling bar shown at the bottom
of the screen during the Windows 98 bootup. Part of it had a
small area that was scrolling by in a black color instead of
the normal blue and white. Normally at a 100Mhz front side bus
setting or greater we would use the 2/3 AGP ratio which is the
only other AGP ratio avialable on the BH6. This lowers the AGP
bus back to 66Mhz at the 100Mhz FSB setting.
Does overclocking the AGP bus help our performance? Let's see.
With the PIII 500E running at 500Mhz, the graphics card at 178Mhz,
and the AGP clocked at 66Mhz I get 69.6 and 62.6 at 640x480
and 800x600 respectively. Setting the AGP to 100Mhz gives me
70.8 and 63.4, about a 1 fps increase. So, yes it will give
some benefit in performance.
Back to the BIOS and lets change the FSB to 124Mhz (124 x 5.0
= 620Mhz) and make sure the AGP clock ratio is set to 2/3. This
puts the AGP clock at 83Mhz which we know is fine with this
Voodoo3. The PCI ratio is at 1/3 which puts the PCI bus at 41Mhz.
Most PCI cards should still run at this setting, but you may
run into some that will object to the faster bus. Running the
benchmarks again with the graphics card set to 178Mhz now produces
a 67.5 and 45.6 at 800x600 and 1024x768 repectively.
At 112Mhz and 124Mhz another item that can effect overclockability
is your RAM memory. Most PC100 RAM should run at 112Mhz, although
its only rated at 100Mhz. At 124Mhz, you need good quality PC100
RAM. The Samsung PC100 RAM that I'm using in this system runs
at this speed with no apparent problems. So, can we push this
system any further? The next FSB setting in the BH6 is 133Mhz.
This is where you would normally go buy some PC133 RAM, but
let's try our system at 133Mhz anyway.
At 133Mhz the AGP bus is now running at 88Mhz (133 x 2 / 3).
We know from the previous testing done in this guide that this
Voodoo3 will handle that with no problems. The PCI clock is
now at 44Mhz (133 / 3). Again you may start to run into some
problems with some PCI cards at this speed. Also, some IDE hard
drives may have problems at this speed. Powering up this system
finds no problems. The system posts and boots into Windows 98.
If you remember at the beginning of this guide I mentioned the
system had a SoundBlaster Live! Value sound card and a generic
(cheap) network card. Neither of these seemed to have
any problems running at the 44Mhz PCI bus speed.
OK, 133Mhz x 5.0 has the PIII 500E clocked at 667Mhz. That's
not too bad. I believe that if we put this CPU on a quality
motherboard with good PC133 RAM, that it would continue clock
right on past the 667Mhz mark with no problems. Now, the benchmarks
show 85.6 and 88.1 at 166Mhz and 178Mhz on the graphics card
at 640x480. Originally with the Celeron 300A clocked at 300Mhz
we could only get 32.1fps. The 800x600 and 1024x768 marks with
the graphics card at 178Mhz shows 67.7 and 45.6. These are virtually
the same numbers that were gotten at the 620Mhz CPU speed. Up
until this point the CPU was limiting the graphics card at these
resolutions. Now the graphics card is beginning to be the bottleneck.
One more step, this time backwards. I mentioned earlier that
the 128MB of RAM was left in and haven't been giving any numbers
to show the differences it may make at this CPU speed. So, removing
64MB of RAM to reduce the total RAM back to 64MB gives me 67.6
and 45.5 at 800x600 and 1024x768, virtually the same. At 640x480
there is a 2 fps drop. With the graphics card at 178Mhz the
1280x1024 video mode produced a max of 28.9 which was initially
reached when the Celeron 300A was overclocked to 450Mhz and
never climbing above that.
Hopefully, you now have a feel for what changes to your system
will provide you with the most performance increase and generally
how much it should cost. Also, if before reading this you weren't
quite sure how overclocking was done, you now have a knowledge
base to work from and hopefully enough confidence to give it
a try. Faster graphics cards and bigger CPUs are the big two
items in your PC that can give you more frags per second, or
if you shoot like me, more feet per second to try and dodge
those rockets! ;-)