58 | MAXIMUMPC | NOV 08 | http://www.maximumpc.com
will gradually tick up as you increase the
front-side bus of your system. It’s somewhat
similar to the gear ratios in a car. As you rev
up the front-side-bus speed, the rpms of the
north bridge can get out of spec and cause a
crash. The strap will adjust the speed of the
north bridge clock independent of the FSB.
The general rule of thumb for overclockers
is to use the lowest strap available that runs
your RAM at the speed you need. This should
enable higher front-side bus overclocks.
The upshot of this is to run in auto mode
if you’re not overclocking and leave it to
the board engineers. If, however, you are
overclocking and seemingly hitting a front-
side bus wall that no amount of voltage will
address, try lowering the north bridge strap
to see if you can push the FSB even higher.GANGED ACTIVITY
If you’re an AMD user and you’re confused
by all this north bridge strap stuff, you can
just ignore it. Since Phenom CPUs feature
the memory controller directly in the CPU
core, there is no memory controller strap to
futz with. What is confusing is the ganged
or unganged mode available in Phenom
boards. Phenom CPUs feature two separate
memory controllers that can be run ganged
or unganged. Generally, you’ll want to run
as unganged to let the controllers operate
independently for best performance.OUT OF THE SKEW
Some motherboards have begun offering the
ability to tweak the “clock skew” for RAM.
In a nutshell, clock skew is the variation in
speed of a module’s individual signal paths
to the memory controller. Skew is the result
of the signal distortion caused by the tracesin the motherboard, the cleanli-
ness of the power going to the
board, and the RAM that’s in
use. Tweaking the skew settings
can help increase stability when
you’re pushing the chipset and
RAM to its limits by overclock-
ing. It’s a game of trial and error
with skew settings, but if you’ve
got the time and energy, it could
help you achieve the few extra
megahertz you were hoping to
get out of your system—just be
ready to roll up your sleeves and
run the POST, crash, reset, POST
routine. If you’re not overclock-
ing, however, you can just ignore
these timings.Just because it’s in the BIOS doesn’t mean you should touch it.
Such is the case with PCI Express overclocking. Notoriously fi n-
icky and known to cause crashing, overclocking the PCI Express
bus in the hopes of getting more GPU performance rarely ends
well. In many cases, overclocking the PCI-E bus by even 1MHz
beyond its stock 100MHz can cause instability. Want a really
good example? Nvidia made much hay of the Linkboost feature
in its 590 SLI and 680i SLI chipsets. Linkboost would automati-
cally overclock the PCI Express slot by up to 25 percent when
paired with GeForce cards.We never could understand the need for Linkboost, as PCI
Express bandwidth was so great to begin with. Nvidia must
agree now too. The company has removed the feature complete-
ly from the newer BIOSes for those motherboards.
You might also be tempted to disable USB legacy sup-
port since the feature lets USB keyboards and mice work in
DOS mode, and, well, who the hell runs DOS anymore? You
do—if you boot into safe mode. With USB legacy support
disabled in safe mode, your USB input devices would be
rendered useless.DON’T DO ITBIOS Tweaks to Avoid
OLD TECH, NEW TWEAKS
Selecting a lower strap but the same RAM speed may help you push the front-side bus speed higher
during an overclocking session.Tweaking the skew for RAM lets you compensate for the
minute signal distortion that occurs with high-speed
parallel interfaces.