Download NVIDIA GeForce2 GTS and GeForce2 MX Voltage

NVIDIA GeForce2 GTS and GeForce2 MX Voltage
Tweaking and Extreme Overclocking
Nowadays one could hardly meet a guy, who has never heard of overclocking. We bet every second
happens to know a chap, who used to call on with a happy smile and a thick layer of thermal paste
over his face, brandishing a bottle of bear and declaring his latest victories - like his old PC that needs
no new CPU, as it lets the games "fly far and fast".
Currently many users tend to buy new CPUs merely for overclocking purposes and start with buying
powerful coolers and choosing a mainboard, which enables them to change the CPU Vcore. This way
they are happy to get a fast system for a pretty modest sum of money. Of course, these are not only
CPUs that are overclocked. Graphics cards are the next in the list of overclockers' preferences. Almost
all of the modern graphics cards can work at over-nominal frequencies and provide a substantial
performance gain. Manufacturers even ship their cards together with frequency-changing utilities. But
still to overclock a graphics card is much more tricky a thing than to overclock a CPU.
However, let's have a try...
Guinea-Pigs
For the investigation we sorted out two graphics cards based on NVIDIA chips.
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SUMA GeForce2 MX Special Edition, boasting a TV-Out, dual-monitor support and 5.5ns
memory. The frequencies for SUMA GeForce2 MX are 175MHz for the core and a
comparatively higher value of 183MHz for the memory.
Asus GeForce2 GTS V7700 with 64MB 6ns DDR memory. By default Asus V7700 works at
200MHz core frequency and 333 (166)MHz memory frequency.
Overclocking
We will try to sweat both the cores and the memories.
As you know, the core and the memory need good cooling to provide stable work at non-standard
frequencies. That's why on the tested platforms we fixed the heatsinks and coolers on a thin layer of
domestic - Russian - thermal paste, KPT-8.
For GeForce2 MX chip on SUMA graphics card we used Blue Orb cooler, while the memory was
equipped with two halves of a heatsink for 80486 CPU.
ASUS 7700 core was equipped with the central part of a cooler for Slot A processors. It is pressed into
the basis and is easy to take out, if you hit it with something heavy. :)
The memory was provided with the best heatsinks we managed to find.
To enable the overclocking, you should create the following section in the registry:
HKEY_LOCAL_MACHINE\Software\NVIDIA Corporation\Global\NVTweak
and introduce a parameter of DWORD type named CoolBits and equal to 3. After that you will get
access to "Hardware" properties page in the driver settings. Now you should enable "Allow clock
frequency adjustments" to be able to set the frequencies equal to over-nominal values and reboot the
system.
The "Hardware" properties page may look something like this:
You needn't restart your computer again every time you change the frequencies.
Here comes only one limitation to stress: NVIDIA drivers allow changing the nominal core and
memory frequencies by the maximum of 25%. Happily enough, this predicament can be avoided.
For this purpose you should first set new core and memory frequencies and make them as close to
the desired figures as possible, for instance like that:
Now look for this section in the registry:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\Display\0000\NVidia\NVTweak\Har
dware:
(if you have several versions of drivers installed, then you may have to use \0001\, \0002\ etc.
instead of \0000\ ). Now copy the content of Krusty key to the neighboring Bart key.
That is all the fuss. Now you may vary the frequencies within the total interval of 50% (i.e. +/- 25%),
but the zero point is assigned to the newly introduced values.
After all the manipulations described above, we obtained the following top frequencies for the two
tested graphics cards:
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220MHz core and 210MHz memory - for SUMA GeForce2 MX;
250MHz core and 400(200)MHz memory - for ASUS V7700.
As for the performance of the cards overclocked that high, we are going to discuss it a bit later in the
article.
And how could one achieve even higher frequencies? Things look very simple when we deal with a
CPU - it's just a matter of the increased Vcore. So, if the CPU is properly cooled, it is quite likely to
please you with tangibly higher frequency rates. However, when it goes about a graphics card, it
appears a much more complicated task to fulfill, since it's a real problem to change the Vcore of the
graphics chip. Besides, it is not at all the fastness of the chip that creates the main limitation for the
today's graphics cards.
Nonetheless, if there is still a chance to increase the Vcore of the graphics chip and of the card's
memory, why should we miss it?
Extreme Overclocking
SUMA GeForce2 MX
The card is equipped with a voltage regulator by UNISEM, a microchip called US1150 (it is marked
with an arrow on the picture below):
This microchip is responsible for controlling the power supply of GeForce2 MX chip. Its full name is
"4A Ultra low dropout positive adjustable regulator". On the picture you can see a typical application
scheme of US1150, which was taken from the datasheet:
The output voltage setting of the US1150 regulator, Vout, can be programmed to any voltages in the
range of 1.25V to 5.5V with the addition of R1 and R2 external resistors according to the following
formula:
The nominal Vcore of GeForce2 MX chip should be 2.05V.
According to our measurements, the Vout of the regulator was 1.92V, while the two resistors (R1 and
R2, named R16 and R17 on the card) indicated 107.4Ohm and 56.9Ohm.
To increase the Vout, you may, for example,
solder the resistor parallel to R1 (named R16 on
the card), like we did (on the typical application
scheme it is highlighted with red color):
This additional resistor provides 120Ohm. Now
the total resistance of R1 makes 58Ohm and the
Vout coming to the chip is 2.5V.
Samsung 5.5ns memory, which you see on the
graphics card, receives the voltage of 3.3V
according to Samsung web-site. This voltage
goes directly via the AGP slot pins from the power
supply unit or mainboard. Therefore, there aren't
many opportunities for voltage adjustment here.
So, the maximum you can set, 3.6V, is possible only if the mainboard allows changing the voltage
(3.3/3.4/3.6V) with a jumper. We were lucky to have ASUS CUSL2 mainboard, which allows
manipulations like that.
The jumper was set in the position to provide 3.6V that's why the graphics memory voltage made
3.69V.
As soon as everything was done, the end frequencies for the graphics card were equal to 265MHz chip
and 210MHz memory.
ASUS V7700
This graphics card also has a UNISEM chip onboard. It is US3007.
This is multifunctional microchip serving as a voltage regulator for mainboards. In case of typical
application it provides 4 stabilized voltages within the interval between 1.3V and 3.5V. Each voltage
can be set separately.
Below is a typical application scheme of this regulator:
In our case, the typical application scheme is used only partially. We have Vout2 and Vout3. Vout2
serves to get 2.5V for the memory buffers and can be derived from the following formula:
Vout3 provides 2V for the core and results from the following formula below:
The voltages can be increased if you shunt R3
and R6 resistors (R811 and R816 as they are
marked on the card) with the additional resistors.
This is exactly what we did: we shunted R811
with a 180Ohm resistor, and R816 - with a
650Ohm one.
As a result the end resistance of R3 and R6 got lower. The core Vout made 2.59V instead of only
2.05V and the memory Vout - 3.12V instead of 2.55V.
As it is stated on Hyundai's site, the DDR memory on the card has a dual power supply: 3.3V for all
the internal circuits and 2.5V for the output buffers. So, we got almost no effect after increasing the
voltage from 2.5V to 3.12V, as all the internal circuits anyway receive 3.3V and we managed to
increase the voltage only for output buffers.
The voltage of 3.3V comes via AGP slot pins and can be slightly modified by the mainboard in case it
allows this option. With the help of the jumper on ASUS CUSL2 , which we used, we reached as much
as 3.69V.
As a result, the working frequencies of ASUS V7700 came to 310MHz for the chip and 410(205)MHz
for the memory.
At last, we turn to the performance.
Testbed and Methods
We assembled the following testbed:
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Intel Pentium III 1000MHz CPU;
ASUS CUSL2 i815E based mainboard;
128MB PC133 with ECC;
Western Digital AC36400-32LC 6.4GB HDD;
Windows98 SE;
NVIDIA Detonator 6.31 driver;
Quake III Arena v1.11 testing application.
We tested in two resolutions: 1280x1024x16 and 1280x1024x32. All the settings in Quake III Arena,
except the color depth and textures, corresponded to High Quality mode. For 1280x1024x32
resolution we set the color depth at 32bit and for 1280x1024x16 we took a 16bit mode. The texture
compression was enabled. Vsync was disabled in the driver. The driver settings stayed at default,
except Vsync and the core and memory working frequencies.
Although the default memory frequency of SUMA GeForce2 MX Special Edition is set to 183MHz, we
tested at 166MHz as well, since 166MHz is a standard default frequency for GeForce2 MX based
graphics cards.
The highest frequencies we obtained for the core and memory were about 5MHz higher than those we
tested with, because at the top frequencies obtained the cards proved utterly unstable. It resulted in
missing polygons and pixels and distorted textures.
We tested a platform assembled without the case at room temperature of 23oC and without any extra
cooling, but for that shown on the photos above.
Each test was run three times. The average result was taken for the charts and diagrams.
Performance
SUMA GeForce2 MX
ASUS V7700
On the following diagrams you can see all the results, shown on a single graph. It allows us top
compare the performance gain by GeForce2 GTS and GeForce2 MX after we have overclocked the
memory and the chip.
Conclusion
Well, what can we say as a final word?
The fact is that, as we surmised, the performance in 32bit color mode remained almost unchanged
even when the card operated at extreme frequencies. The graphics memory bus bandwidth acts as a
grave limitation in 32bit mode and badly affects the performance in 16bit mode. By overclocking the
core of GeForce2 GTS, for instance, we hardly observed any performance gain even in 16bit mode.
Indeed, it turned out unreasonable to undertake extreme overclocking of GeForce2 GTS core as it
proved too hard to do. The only thing we can pride ourselves on is the remarkably high frequency
achieved.
GeForce2 MX is equipped with SDR memory, which works at lower frequencies if compared with those
of the core. In the long run it leads to a complete dominance of the memory as a performance
determinant by overclocking in 32bit color mode.
However, in 16bit mode we were surprised to see an appreciable performance gain: with the initial
memory frequency of 210MHz the growth totaled circa 25%. When the memory frequency is 166MHz
the gain equals to 11%. By the by, when we locked the core frequency at 175MHz and overclocked
the memory alone, the greatest difference reached only some feeble 8%, while in case of 265MHz
core frequency the gap rose up to 22%.
An interesting thing happened when we overclocked the memory of GeForce2 MX in 16bit mode - it
was less fruitful than extreme overclocking of the core.
The ultimate performance gain in 16bit mode, when the core and memory were overclocked to their
maximum, climbed up to tremendous 36% (!)
Considering all the above mentioned facts, we can assume that those who suffer from the poor
overclockability of the memory on their GeForce2 MX can take the trouble of making some simple
resoldering and squeeze the maximum of the graphics core. It seems to be quite enough to improve
the card's performance in 16bit color mode, but there are still some remarks to pay attention to.
Remarks:
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This material is just a kind of experiment and we do not aim to encourage extreme
overclocking and resoldering of graphics cards.
The described modification of the card shortens the card's service and lifetime.
Whatever changes the user introduces to the card, he loses his right for warranty service.
If the graphics card or some other bundles get wrecked, the user has to bear the entire
responsibility.