For about $330, the Intel Sandy Bridge-based
Core i7-2600K quad-core processor represents
an excellent value for performance-conscious
enthusiasts. With decent cooling, some tweaking
know-how, and a little bit of luck, an overclocked
Core i7-2600K can perform on par with or even
better than Intel’s current flagship 6-core processor,
the Core i7-990X.
Intel’s Sandy Bridge-based second-gen
Core processor family arrived back
in January to much fanfare. The new
processors offered significant performance
gains over the previous generation, an
integrated graphics core that was head and
shoulders above anything Intel had offered
before, lightning-fast video encoding, and
impressively low power consumption. Save
for a few quibbles here and there, it seemed
that Intel had hit one out of the ballpark.
A few weeks after launch, however,
troubling news of a defect in the 6 Series
chipset that affected the reliability of its
3Gbps SATA ports halted shipments and
forced a recall—highly disappointing for
enthusiasts itching to upgrade, to say the
least. The problem was immediately
identified and quickly remedied, though,
and by the time you read this, motherboards
based on the fixed B3 revision of the 6 Series
chipsets should be plentiful on store shelves.
Let the upgrades begin!
Now that Intel has ironed out Sandy
Bridge’s initial wrinkles, we thought
it was the perfect time to find out what
the platform could really do. Armed with
the fastest Sandy Bridge-based processor
available, the Core i7-2600K, and an
enthusiast-class motherboard from Asus,
the P8P67 Deluxe, we set out to overclock
the 2600K using nothing but air-cooling.
OC Prerequisites
There are a few things prospective
Sandy Bridge overclockers need to know.
First, much of what we’ve all learned about
overclocking with older parts is no longer
relevant. Intel has made some changes to
the platform that make BCLK adjustments
next to useless. The current D2-stepping
processors don’t react well to sub-zero temps
or super-high voltages, and disabling sleep
states or Turbo Boost isn’t necessary. In
fact, it’s the Turbo Boost settings that need
to be altered to overclock a Sandy Bridge
processor. At this time, users must also have
a P67-chipset based motherboard, preferably
targeted at enthusiasts, to overclock a Sandy
Bridge CPU like the Core i7-2600K. The
other members of the 6-series
chipset family simply don’t
allow it at this time.
For the largest speed gains,
Sandy Bridge overclockers
must also opt for a K series, or
fully unlocked, CPU. Non-K
series parts are only partially
unlocked and can’t be pushed
nearly as far with the limited
multiplier and BCLK settings
currently available.
With the relative immaturity of the
platform, it’s also very important to stay up
to date with EFI or BIOS updates. With
the Asus motherboard we used for this
project, each successive EFI update changed
the overclocking characteristics, and some
of the updates even had features specifically
designed to boost the overclocking capabilities.
Motherboard manufacturers are still
mastering the inner workings of the Sandy
Bridge platform, so keeping the mobo up to
date is definitely a good idea.
Finally, as has always been the case, good
cooling is also a must. Sandy Bridge-based
processors are particularly power-efficient and
have fine-grained clock-gating capabilities,
though; you may be surprised how far the
chips can be pushed with nothing but a
quality air cooler. To prove this point, we
stuck with Intel’s XTS100H cooler, which
ships with K series Sandy Bridge processors.
The Intel XTS100H tower-type
cooler included with Socket
LGA1155 Core i5 and Core
i7 K series processors
does a respectable job of
keeping CPU temperatures
in check. Using this “stock”
cooler, we were able to
push a Core i7-2600K to over
4.6GHz with perfect stability
and zero throttling.
Mod Mania
With many of the enthusiast-class
P67-motherbaords on the market, you
can overclock Sandy Bridge processors
a couple of ways. On our P8P67 Deluxe,
for example, the main BIOS screen has a
simple performance option that, with
a simple click of a button, will
push the processor up a few ticks
when Turbo is engaged. For
more granular control, though,
manually manipulating some
settings is the way to go.
For a straight-up CPU overclock,
you’ll need to alter the
following three settings: peak
Turbo Boost multiplier, CPU
core voltage, and, for a bit
more performance, the BCLK.
Admittedly, BCLK adjustments
will offer only minor boosts because
most Sandy Bridge processor and P67
motherboard combinations won’t hit BCLK
frequencies higher than about 105MHz,
a paltry 5% increase over the default. For
more aggressive overclocks, you can adjust
memory frequencies with K series processors
and, of course, a number of motherboardlevel
components can also be tweaked in an
attempt to eke out a little more performance.
By default, the Core i7-2600K has a base
multiplier of 34, for a standard frequency
of 3.4GHz (34 x 100MHz) and a peak
Turbo Boost frequency of 3.8GHz, which
is attained by boosting the multiplier to
38. With K series Sandy Bridge processors,
although a peak Turbo Boost multiplier
of up to 57 is available (for a technical
peak of 5.7GHz), you’re not likely to hit
speeds that high without some exotic system
mods. To overclock the Core i7-2600K,
all that is necessary is to increase the peak
Turbo multiplier until the maximum stable
frequency is reached.
In addition to adequate cooling,
overclocking Sandy Bridge-based
processors at this time requires one
more thing: a P67-based motherboard
designed with overclocking in
mind. There are a number of quirks
associated with overclocking Sandy
Bridge-based processors, and if the
motherboard isn’t designed to cope
with them, keeping a system stable
will be difficult.
For our mod, we first entered the motherboard’s
EFI configuration menus and
boosted the processor’s voltage to 1.35V, a
0.16V bump from the stock voltage. If you
want to test the waters with voltages higher
than that, we’d suggest using high-end air- or
liquid-cooling. With the voltage increased,
we bumped the Turbo multiplier to 40, then
booted Windows and looped Cinebench
11.5 to fully tax the processor at 4GHz to
check for stability. We were good to go, so we
re-booted again, raised the multiplier further,
and ultimately found a multiplier of 46, for
an effective top speed of 4.6GHz, was our
max. At 47, the system wasn’t perfectly stable.
At that point, we backed
the multiplier down to 45 and
began to adjust the BCLK.
The BCLK topped out at only
103MHz, for a final peak clock
speed of 4.64GHz. We could
have stopped with the multiplier
set to 46, but by altering the
BCLK, even if only a little bit, we
ultimately ended up with a higher
peak overclock and a slight boost
to memory bandwidth. (Altering
the CPU multiplier alone won’t
affect memory performance.)
Sandy Bridge Rocks
Although the overclocking process for
Sandy Bridge is somewhat different than
previous generations, it’s still quite easy,
and the performance gains can be massive.
Making a $330 quad-core processor
outperform a $1,000 6-core Intel CPU
required nothing more than a good
motherboard and the stock Intel cooler.
Sandy Bridge may not offer all of
the overclocking freedom of older Intel
platforms, but there’s still plenty of fun to
be had and performance to be gained.
Many enthusiast-class P67-based motherboards
are outfitted with EFI (Extensible Firmware Interface),
which is a replacement for the aging system BIOS.
Some of the EFI configuration menus on these
enthusiast-class boards offer simple one-click
overclocking options.
Performance: Before & After The Mod
We ran a handful of popular
applications and benchmarks
to see just how much additional
performance we were able to
extract from our overclocked
Core i7-2600K-based system.
In the chart presented here, we
have benchmark scores from
the following three test-bed
configurations: the stock Core
i7-2600K, the Core i7-2600K
overclocked to 4.64GHz, and Intel’s
current flagship Core i7-990X six-core
processor running at its stock speeds.
The numbers tell an interesting
story. Obviously, overclocking the
Core i7-2600K to 4.64GHz resulted
in some large performance
gains. The overclocked processor
outpaced its stock counterpart by
margins ranging from 13.3% to
42.47%. The smallest gains were
realized in the SiSoft Sandra
memory bandwidth benchmark
and in the less taxing LAME
MT encoding tests. The gaming
tests and processor-intensive
rendering benchmarks showed
the largest improvements.
Comparing the performance of
our overclocked Core i7-2600K
to the Core i7-990X processor
proves that you don’t need to
spend $1,000 on a CPU to have the
fastest rig on the block. Although
it wasn’t a clean sweep, the overclocked
quad-core Core i7-2600K
was faster than the six-core
Core i7-990X in four of the eight
benchmarks we ran, and in three of
the tests where the Core i7-2600K
trailed Intel’s flagship, the delta
separating the two processors was
less than 5%.
Article From : Computer Power User Magazine
Article By Computer Power User Magazine
