Two different parts of a video card may be overclocked, the GPU (Graphics
Processing Unit) and the RAM. In addition, disabled pipelines on a video card
may also be enabled through third-party drivers, third-party software, or direct
hardware modifications depending on your video card type. Overclocking a
video card is usually done through third-party or proprietary software.
Recent ATI proprietary Catalyst drivers feature an interface called Overdrive
that allows for dynamic GPU frequency scaling based on its temperature
and load. Increase the load, the clock rate increases for performance, but it’s
balanced against the increasing temperature. Sufficient for simple increases in
overall performance, this doesn’t allow for the best performance increase which
requires overclocking the memory. For that you’ll need third-party applications
or drivers.
An application example is ATITool. This program has many options, including
GPU and memory overclocking, temperature monitoring, and fan control,
allowing for a much more complete solution to overclocking ATI based video
cards. There are many third party drivers, omegadrivers.net, for example hosts
ATI and nVidia drivers as well. Both of which include integrated overclocking
and many unlocked features, including enhanced image quality for nVidia-based
cards.
nVidia video cards can also be OCed through a hidden feature in the driver
called coolbits. Coolbits is a feature that can be unlocked by creating a DWORD
in regedit for windows operating system. To use the coolbits feature, for windows
just simply open the regedit then open the directory HKEY LOCAL MACHINE
> Software > NVIDIA Corporation > NVTweak and create a new DWORD
value in the NVTweak folder named coolbits then right-click it¿modify type 3
for single card or 1A for SLI in the value name .It is a good a overclocking tool
as it has a fairly conservative “optimal clock” once you have thus increased the
core clock (not the memory clock!!) run a gpu intensive task like 3dmark, repeat
until you have a sudden drop in the benchmark score. This is the thermal
throttling kicking in; do not push it any harder as it will result in permanent
damage to your gpu. Back off the clockspeed by about 20-30mhz
The most important thing to remember about overclocking a video card is
cooling. This can’t be stressed enough. Just as a CPU can be damaged or have
a shortened lifespan by overclocking or excessive and prolonged heat, so can a
video card. In the past year many inexpensive and easy to install options have
surfaced for cooling a video card, from adhesive ram heatsinks which attach
to un-cooled ram chips, to rather expensive water-cooling solutions. A good
midpoint (both in cost and effectiveness) solution is to purchase and install a
direct exhaust, “sandwich” cooling solution. Direct exhaust means all air from
the cooling fan is blown across the video card and directly out of the computer
case, usually using the open PCI slot below the AGP (or PCIe) slot. This allows
for substantially lower GPU temperatures.
A sandwich cooler is two aluminum or copper heatsinks, shape formed for a
particular video card, that “sandwiches” the video card in between the two and
are usually connected by some kind of copper heat pipe which allows for the
hotter side to convey heat to the cooler side for dissipation. The GPU should
never surpass 60 degrees Celsius for optimal performance and to avoid damaging
the card. Most of the latest video cards are rated to go up to 90c, but this is
NOT recommended by anyone. The optimal temperature for a video card is
40-55c for the card itself (the GPU’s temperature differs depending on which
you have,) but the lower you can get it, the better.
One important thing to note. Many think that the option which says “AGP
voltage” in their BIOS can be used to “voltmod” a video card to get a bit more
power out of it. In fact, it’s used for something else, and raising the AGP voltage
can and probably will cause damage to a video card.