Many of you looking to
upgrade to a Super7 system have contacted me requesting information on the overclocking
abilities of the K6-2. It is because of this that I have decided to pursue this
undertaking. The following article will be full of tips and warnings as well as a
few benchmarks, but because every system is different, the results you get may vary
Many of you have successfully overclocked either your Pentium MMX, AMD K6, and even in
some cases your Cyrix 6x86's. In doing so you've gained some knowledge about your
systems and in particular:
Processor Cooling Techniques
Core Voltage Capabilities and Settings
Fluctuations in the PCI bus frequency and it's resulting affect on your peripherals
The Stability of the DRAM at higher CPU bus speeds
Having mastered or at least attained a basic knowledge in these four areas you probably
pushed the limits of your processors capabilities. Now with Super7 technology pushing
front side bus speeds up to and even above 124MHz you may only need to do a little
rethinking. While at speeds up to 100MHz the Super7 platform's PCI clock divider
limited the PCI bus speed to 33MHz, increasing the FSB will again cause fluctuations in
the PCI bus and at speeds this high you will not only need PC100 SDRAM but you will need
high quality 7ns or lower, CAS 2 latency PC100 if you desire to effectively overclock your
processor with any degree of stability.
Super7 processors performance relies on the external speed of the CPU to determine how
fast it can transfer data to and from the L2 cache. The increase from the old 66MHz
external bus speed to Super7's 100MHz bus speed results in a major performance gain that
is reduced dramatically when not using the 100MHz setting. For instance, the performance
level of the K6-2 300 overclocked to 332MHz (4.0 x 83MHz) will be less than the
performance level at it's rated 300MHz (3.0 x 100MHz) because the 83MHz bus speed affects
system performance more than the higher clock multiplier rate.
K6-2 300MHz Processor
As far as I can tell this CPU is sold at just about it's peak performance. In a dozen or
so tries I could only get Windows 98 to load only once when running the chip at 100MHz x
3.5 with a high core voltage of 2.5v and as such can't recommend this chip as any kind of
overclocking candidate. It does perform with a reasonable amount of stability
when running the front side bus at 112MHz even at a core voltage of 2.3v (remember, it is
important to set the voltage at the lowest possible setting at which the chip will run
with stability) but heats rapidly when called upon for floating point intensive
applications such as QuakeII; setting off the CPU temperature alarm (66C/151F) before
completing even one Massive1 timedemo, using a regular heatsink and fan combination.
Changing the setup to an oversize heatsink and using a case fan instead of one that is
mounted to the heatsink itself overcame all heat related concerns as far as my system was
concerned though and the CPU ran like a champ from then on. Running the processor at
333MHz (95MHz x3.5) proved unsatisfactory, only loading Windows about 50% of the
K6-2 333MHz Processor
The K6-2 333 shows a bit more promise than its little brother in the area of
overclockability. Running the chip at 350MHz is easily accomplished with the FSB
running at 100MHz and the clock cycle at 3.5 even with the core voltage set at the default
2.2v. This fact alone leads me to wonder about the recently released K6-2 350MHz
chip and its overclocking capabilities. The chip is also capable of reasonably
stable performance at 380MHz (95MHz x 4.0) with a core voltage setting of a medium-high
2.4v. With the oversize heatsink and case fan combination the processor rarely
generated more than 62C, well within its normal operating range.
Unfortunately, I have yet to receive my rev. 1.1b of the VA-503+ so for most of the
tests I used my existing FIC VA-503+ with the "CD' rev. of the MVP3 chipset. The
board itself is astoundingly stable at the 112MHz FSB and has the capability of
adjusting the voltage in 0.1v. steps but for some tests I used the Epox 58-MVP3E-M ATX
mainboard (w/rev. "CE" of the MVP3 chipset) because of its ability to run the
FSB at 95MHz. Before starting any serious testing I had experimented with using a
PCI video card but the processors seem to run quite a bit hotter when testing graphics
intensive performance using the ATI All in Wonder Pro 8 MB PCI graphics card and
though I know of no particular reason for this ( and I do intend
to follow-up on this
) I decided to use the Viper 330 AGP 4MB card. Using
the AGP card the processors ran at least 8% and as much as 22% cooler when
overclocking. Always starting with the default voltage recommendations, voltages
were raised in 0.1v increments when using the VA-503+ but on the Epox board I decided it
wouldn't be prudent to exceed the 2.4v. setting as the next step up is 2.8v which would
almost certainly mean too much heat and would most likely result in damage to the
processors. Thermal paste was used between the processors and heatsink to assist in the
cooling process, and the machine was run for a minimum of 6 hours doing general business
applications before running any of the benchmarks shown below. Each benchmark was
run three times and then averaged to reflect the scores that you will see below.
Either board was equipped with a single Corsair PC100 64MB DIMM with a CAS latency of 2
and memory accesses within the BIOS were set to the fastest settings available.
As you can see the higher the front side bus the better the performance.
The K6-2 300 actually outperforms the the 333 when it runs at 112MHz and the 333 is
running at either 95 or 100MHz until you get the 333 up to about 380MHz
Although the CPUmark32 slightly favors the increased clock rate the FPU
Winmark is again higher when the FSB is increased...
Pretty impressive 3D Winbench marks even with a relatively unimpressive video card...
What it all comes down to is that while you can push more performance
out of these processors, it may be worth waiting to see what AMD has up
their sleeve with the K6-2 350 although it seems a little pricey.
Before attempting to overclock your processor it is a good idea (unless you have some
experience) to read our Overclocking Guide. Make sure that you understand that AMD
does not recommend running your processor at speed other than those specified by the
manufacturer. If you burn up your processor they will not replace it nor will your
mainboard manufacturer. You will be in effect voiding any warranty granted by any of
your hardware device manufacturers.
I hope to get ahold of the K6-2 350 soon and will do a full review. Until then I
am happily running my machine at it's recommended bus speed and clock rate and I am happy
with the result as well as the peace of mind. If you like to tinker and don't have
any data that you can't afford to lose have at it and have fun...
Last Updated on 9/3/98