ZOTAC GeForce GT 640 ZONE Edition Fanless GPU

Table of Contents

Budget graphics cards aren’t as exciting as the top tier models but their lower power requirements are perfect for quiet or even silent cooling. ZOTAC has taken advantage of the GeForce GT 640’s modest 65W TDP, equipping it with a completely fanless cooling solution.

September 17, 2012 by Lawrence Lee

ZOTAC GeForce GT 640 ZONE Edition
PCI-E Graphics Card
Street Price

The GeForce 600 series have been getting fairly good reviews since their release. NVIDIA’s new 28 nm Kepler core is the driving force behind their new cadre of high performance, energy efficient graphics cards that are fairly competitive with AMD’s HD 7000 series. Improvements in this latest generation include an updated video decoder that can render 4K resolutions, support for up to four displays, and PCI Express 3.0. They’ve also thrown in GPU Boost, which overclocks the GPU dynamically based on the current power draw (similar to features found on AMD and Intel CPUs) but only for the GTX 660 and higher.

As usual, many of the lower models have gotten lost in this launch, even though most GPU sales occur at the more modest price-points. These slower cards don’t promise the buttery performance of its higher-end counterparts but with lesser hardware inside, they use less power, opening up the possibility of quiet or even silent cooling. While powerhouses like the GeForce GTX 680 and 670 are impressive technological specimens, you won’t see one outfitted with a fanless heatsink anytime soon. The lower echelon of the GT 600 series is better suited due to more thrifty energy requirements; they carry TDPs of 65W or lower.

Low-End Retail GeForce 600 Series Comparison
Card Model
GT 620
GT 630
GT 640
GT 650
Mfg. Process
40 nm
40 nm
28 nm
28 nm
Transistor Count
585 mil.
585 mil.
1300 mil.
1300 mil.
CUDA Cores
Core Clock*
700 MHz
810 MHz
900 MHz
1058 MHz
Memory Clock*
1800 MHz
1800 MHz / 3200 MHz
1782 MHz
5000 MHz
Memory Bandwidth
14.4 GB/s
28.8 GB/s / 51.2 GB/s
28.5 GB/s
80 GB/s
Street Price
US$109 (MSRP)
*reference clock speeds, actual speeds vary from model to model

Today we’re looking at ZOTAC’s GeForce GT 640 ZONE Edition which features a completely fanless heatsink. Like most US$100 GPUs, the GT 640 is a compromise model, not quite a serious gaming card but not a simple 2D/HTPC model either. Its 3D performance is greatly improved over the lower rungs on the ladder, however. Compared to the GT 620 and 630, it has more than twice as many transistors, more than thrice the number of CUDA cores (stream processors) and a higher core clock speed as well. However, it is saddled with same slow DDR3 memory which can be quite detrimental to performance. There’s a full 2GB offered on the reference model which is excessive on a budget card; it increases cost and most of it will likely go unused.

It should be noted while the 28 nm Kepler core is found exclusively n the GeForce 600 series, some of models actually use the old 40 nm Fermi core. NVIDIA has a habit of rebranding old cards to fill various price-points. Retail GT 620’s and 630’s are actually rebadged GT 530’s and 540’s respectively but Kepler can be found in the OEM versions sold to system integrators like Dell, HP, and Lenovo. Also note that manufacturers often put out more than one SKU of a card with varying core and/or memory speeds, i.e. not all GT 640’s are made equal.

The box.

Package contents.

The GT 640 ZONE Edition ships in a modestly sized package consisting of the card itself, documentation, a driver/software disc, a DVI to VGA adapter, and a 3-day pass for TrackMania 2: Canyon, a well-reviewed racing game from Ubisoft.

GPU-Z screenshot.

The listed specifications and GPU-Z both confirm that the ZONE Edition has the exact same specifications as the reference model.

ZOTAC GeForce GT 640 ZONE Edition (ZT-60204-20L):
(from the product
web page


The ZOTAC GeForce GT 640 ZONE Edition is 18.4 cm long measured from the edge of the PCB at the rear panel to the far edge of the heatsink. It weighs 340 grams with the heatsink accounting for 220 grams of the total.

The visible portion of the heatsink consists of 3 x 6 mm copper heatpipes and a substantial stack of aluminum fins approximately 0.36 mm thick and spaced 2.57 mm apart on average. The fins wrap around the edge of the PCB, increasing its length from 14.5 cm to 18.4 cm.

The heatpipes also protrude outward making it 2.8 cm wider than normal. This makes it incompatible with slimmer cases that have just enough space for a full profile graphics card.

Though it’s a two slot card, the heatsink doesn’t fill up the entire allocated space. Passive coolers need breathing room.

There are three display outputs at the back, one mini-HDMI, one DVI-D, and one DVI-I. A DVI-I to VGA dongle is included but a mini-HDMI adapter was omitted from the package.

Getting under the hood is a simple matter of removing the four spring-loaded screws around the GPU core. The core has a shim surrounding it to protect from over-tightening the heatsink but there are also four rubber pads on each side as a further preventative measure.

Heat is transferred from the GPU core through thick thermal compound to a large, flat copper base soldered to the heatpipes.


Our test procedure is an in-system test, designed to:

1. Determine whether the cooler is adequate for use in a low-noise system.
By adequately cooled, we mean cooled well enough that no misbehavior
related to thermal overload is exhibited. Thermal misbehavior in a graphics
card can show up in a variety of ways, including:

  • Sudden system shutdown, reboot without warning, or loss of display signal
  • Jaggies and other visual artifacts on the screen.
  • Motion slowing and/or screen freezing.

Any of these misbehaviors are annoying at best and dangerous at worst —
dangerous to the health and lifespan of the graphics card, and sometimes to
the system OS.

2. Estimate the card’s power consumption. This is a good indicator of how efficient
the card is, and it affects how hot the GPU runs. The lower the better.

3. Determine how well the card decodes high definition video.

Test Platform

Tested Cards

Card Model
Core Clock
AMD Radeon HD 5450
650 MHz
512MB GDDR3 (900 MHz)
HIS Radeon HD 5550
550 MHz
512MB GDDR5 (1000 MHz)
AMD Radeon HD 6570
650 MHz
512MB GDDR5 (1000 MHz)
Sapphire Radeon HD
7750 Ultimate
800 MHz
1GB GDDR5 (1125 MHz)
ASUS Radeon HD 6850

(EAH6850 DC/2DIS/1GD5)
790 MHz
1GB GDDR5 (1000 MHz)
AMD Radeon HD 6870 + GELID Icy Vision @5V
900 MHz
1GB GDDR5 (1050 MHz)
HIS Radeon HD 5870
iCooler V Turbo
GELID Icy Vision @5V
875 MHz
1GB GDDR5 (1225 MHz)
ASUS GeForce GT 430
700 MHz
1GB DDR3 (800 MHz)
ZOTAC GeForce GT 640 ZONE Edition
902 MHz
2GB DDR3 (891 MHz)
ASUS GeForce GTS 450

783 MHz
1GB GDDR5 (902 MHz)
Gainward GeForce
GTX 560 Ti Phantom
823 MHz
2GB GDDR5 (1002 MHz)
ASUS GeForce GTX 680
DirectCU II OC

1020 MHz*
2GB GDDR5 (1502 MHz)
*GPU Boost up to 1111 MHz (1084 MHz according to specifications)

Measurement and Analysis Tools

3D Performance Benchmarks (for low-end/budget graphics processors only)

Estimating DC Power

The following power efficiency figures were obtained for the
Kingwin LZP-1000
used in our test system:

Kingwin LZP-1000 Test Results
DC Output (W)
AC Input (W)

This data is enough to give us a very good estimate of DC demand in our
test system. We extrapolate the DC power output from the measured AC power
input based on this data. We won’t go through the math; it’s easy enough
to figure out for yourself if you really want to.

Ambient Noise Level

Our test system’s CPU fan is a low speed Scythe that is set to full speed at all times. The two Antec TrueQuiet 120 case fans are connected to the motherboard and are controlled using SpeedFan. Three standard speed settings have been established for testing.

GPU Test System:
Anechoic chamber measurements
System Fan Speed
System SPL@1m
High (loud)
1130 RPM
26 dBA
Med (quiet)
820 RPM
18 dBA
Low (silent)
580 RPM
12~13 dBA
Note: mic is positioned at a distance of one meter from the center of the case’s left side panel at a 45 degree angle.

When testing video cards and coolers with active cooling, the low setting will be used. For passive cards and heatsinks, all three settings will be tested to determine the effect of system airflow on cooling performance.

Video Test Suite


1080p | 24fps | ~22 mbps

H.264/MKV: A custom 1080p H.264 encoded clip inside an Matroska container.


1080p | 24fps | ~2.3 mbps

Flash 1080p: The Dark Knight Rises Official Trailer #3, a YouTube HD trailer in 1080p.


Testing Procedures

Our first test involves monitoring the system power consumption as well as CPU and GPU temperatures during
different states, idle, under load with Prime95 to stress the processor, and Prime95 plus FurMark to stress both the CPU and GPU simultaneously. This last state is an extremely stressful, worst case scenario test which generates
more heat and higher power consumption than can be produced by a modern video
game. If the card can survive this torture in our low airflow system, it should be
able to function normally in the vast majority of PCs. Noise levels are measured and recorded as well; if we deem the card’s fan control to be overly aggressive, we can adjust them at our discretion using various software tools.

Our second test procedure is to run the system through a video test suite featuring
high definition clips played with PowerDVD and Mozilla Firefox (for Flash video). During playback, a CPU usage graph is created
by the Windows Task Manger for analysis to determine the average CPU usage.
High CPU usage is indicative of poor video decoding ability. If the video (and/or
audio) skips or freezes, we conclude the GPU (in conjunction with the processor)
is inadequate to decompress the clip properly.

Lastly, for low-end and budget graphics cards, we also run a few gaming benchmarks to get a general idea of the GPU’s 3D performance. We don’t feel this is necessary for high-end models as there are many websites that do this in painstaking detail.

GPU Cooler Testing

Heatsink testing requires only the Prime95 plus FurMark stress test to be used. The fan(s) (if applicable) are connected to a custom external fan controller and tested at various speeds to represent a good cross-section of its airflow and noise performance.

Our GPU cooler test card is an HIS Radeon HD 5870 iCooler V Turbo, a factory-overclocked single GPU card that draws about 236W by our estimates. The stock VRM heatsink is left on for convenience.


Baseline Power with Integrated Graphics:

Power Consumption Measurements:
GPU Test System (Intel HD 2000 IGP)
CPU Load
CPU + GPU Load
Sys. Power (AC)
Sys. Power (DC)
System fan speeds: Low
Ambient noise level: 10~11 dBA
System noise level: 12~13 dBA

System with Discrete Graphics:

System Measurements: GPU Test System
(ZOTAC GeForce GT 640 ZONE Edition)
CPU Load
CPU + GPU Load
System Fan Speed
SPL @1m
12~13 dBA
18 dBA
26 dBA
Sys. Power (AC)
Sys. Power (DC)
Ambient noise level: 10~11 dBA
Ambient temperature: 22°C

With our test system fans on our low speed, 12~13 dBA@1m setting, the GT 640 ZONE Edition ran fairly cool and was also very energy efficient with only 45W being pulled from the wall outlet. On load, the GPU temperature gradually climbed until it reached 99°C and then suddenly leveled off even though the rate of temperature increase hadn’t really slowed at that point. It stayed at 99°C indefinitely but we assume this was a bug and that the actual temperature topped 100°C. Interestingly, the card remained stable during this time..

In any event, 99°C was still fairly hot so we increased the system fan speed to the medium setting (18 dBA@1m). After a few minutes the GPU temperature sensor started responding again, dipping down to 98°C. It took our high speed setting (26 dBA@1m) before it dropped to the reasonable temperature of 89°C.

It was a disappointing result — If you need to crank up your system fans to achieve a decent level of cooling, it negates much of the advantage of having passive heatsink. To be fair our test is more stressful than any real world situation but it can come close depending on the climate and other system components. Either way, we can’t recommend using this card in a very quiet or close to silent system with minimal airflow. It needs a little help or it will become quite toasty on load.

Power Consumption

The power consumption of an add-on video card can be estimated by comparing the total system power draw with and without the card installed. Our results were derived thus:

1. Power consumption of the graphics card at idle — when Prime95 is run on a system, the video card is not stressed at all and stays idle. This is true whether the video card is integrated or an add-on PCIe 16X device. Hence, when the power consumption of the base system under Prime95 is subtracted from the power consumption of the same test with the graphics card installed, we obtain the increase in idle power of the add-on card over the integrated graphics chip.

2. Power consumption of the graphics card under load — the power draw of the system is measured with the add-on video card, with Prime95 and FurMark running simultaneously. Then the power of the baseline system (with integrated graphics) running just Prime95 is subtracted. The difference is the load power of the add-on card. Any load on the CPU from FurMark should not skew the results, since the CPU was running at full load in both systems.

Both results are scaled by the efficiency of the power supply (tested here) to obtain a final estimate of the DC power consumption.

Note: the actual power of the add-on card cannot be derived using this method because the integrated graphics may draw some power even when not in use. However, the relative difference between the cards should be accurate.

According to our calculations, the GT 640 ZONE Edition consumed about 9W when idle and 45W on full synthetic load, about the same as the Sapphire HD 7750 Ultimate. 9W idle is fairly impressive, edging out most of the low-end AMD cards we’ve tested in the past.

All of the AMD/NVIDIA cards from the last three generations had very similar CPU usage during video playback, 1~2% for our 1080p H.264/MKV test clip, and 8~9% for our YouTube HD sample. Power consumption however varied greatly, dependent mostly on the core/memory clocks used by the cards’ respective video decoder chips. This favors the NVIDIA cards as most of them utilize much lower clock speeds.

The GT 640 is among the most frugal cards when playing video, increasing the system power consumption by only about 5W. Add this to its already low idle draw, and it’s an impressively efficient GPU for a media PC.

Noise & Cooling

Comparison: GPU Test System (Load)
GPU Temp
SPL @1m
Sapphire HD 7750 Ultimate*
12~13 dBA
ZOTAC GT 640 ZONE Edition*
(sys. fans on med)
18 dBA
ASUS GTS 450 DirectCU
26 dBA
ZOTAC GT 640 ZONE Edition*
(sys. fans on high)
26 dBA
AMD HD 6570
27~28 dBA
System fans on low (12~13 dBA@1m) unless otherwise noted.
Ambient temperature: 22°C
*passively cooled

The passively-cooled Sapphire HD 7750 Ultimate occupies the same price-point as the GT 640 ZONE Edition, making an appropriate card for a direct comparison. It simply puts the GT 640 to shame, maintaining a load temperature under 80°C with our silent 12~13 dBA@1m fan speed setting. The GT 640 ran more than 21°C hotter with our quiet 18 dBA@1m setting, and was still 12°C behind using our loud 26 dBA@1m setting.

The ASUS GTS 450 DirectCU, which is in a similar class as the GT 640, was also more noise efficient. Despite having an an over-aggressive fan, its system noise level on load also hit 26 dBA@1m but it had the advantage of having 23°C of headroom.

3D Performance

Our synthetic benchmarks paint the GT 640 as a solid budget contender, falling somewhere between the GDDR5-equipped Radeon HD 6570 and GeForce GTS 450 in performance.

In our two easier game benchmarks, Crysis and Lost Planet 2, the GT 640 managed to produce playable frame rates at 1680×1050 resolution with medium detail. The results were disappointing however when you consider how well the HD 6570 managed to keep up.

Sniper Elite V2 and Aliens vs. Predator presented more difficult challenges for the GT 640, requiring us to reduce the detail level in Sniper Elite V2 to low and drop the Aliens vs. Predator resolution to 1440×900. And once again, the GT 640 was unable to beat the HD 6570.

MP3 Sound Recording

This recording was made with a high
resolution, lab quality, digital recording system
inside SPCR’s
own 11 dBA ambient anechoic chamber
, then converted to LAME 128kbps
encoded MP3s. It’s intended to give you an idea of how our test system sounds
in actual use — one meter is a reasonable typical distance between a computer
or computer component and your ear. The recording contains stretches of ambient
noise that you can use to judge the relative loudness of the subject. Be aware
that very quiet subjects may not be audible — if we couldn’t hear it from
one meter, chances are we couldn’t record it either!

The recording starts with 5~10 seconds of room ambiance, followed by 5~10 seconds
of the GPU test system with its case fans at various speeds. For the most realistic results, set the volume
so that the starting ambient level is just barely audible, then don’t change
the volume setting again.


The ZOTAC GeForce GT 640 ZONE Edition is a fairly unremarkable fanless video card. The cooler is nothing special, not overly large or particularly clever or effective. It requires a good amount of airflow to keep the GPU adequately cool, barely managing a core load temperature under 100°C in our torture test with two case fans running at quiet levels. Like most low-end models, the board itself is quite small but two expansion slots are required because of the girth of the heatsink and for breathing room; it also takes up a bit of extra space on the trace side of the PCB as the cooler partially wraps around the edge of the card.

As a gaming card, the GT 640 is a real let-down, possibly because it’s saddled with a whopping 2GB of slow DDR3 memory rather than a more pragmatic amount of faster GDDR5. In our tests, it was capable of producing playable frame rates in various games at 1440×900 and 1680×1050 resolution with vary degrees of detail but struggled to keep up with the Radeon HD 6570 and was soundly beaten by the GeForce GTS 450. Keep in mind GT 640’s start at US$90, similar to the GTS 450, while the HD 6570 is about $20 cheaper. The ZONE edition isn’t widely available at the time of writing but we did find it on one website for a whopping US$120. At that price, the Sapphire HD 7750 Ultimate offers substantially more value with far superior performance and a larger, more capable heatsink. As it stands, the GT 640 is too expensive and the ZONE Edition only compounds the problem.

The only area in where the GT 640 stands out is energy efficiency. It was one of the most frugal cards we’ve tested, consuming about 9W when idle and only 4~6W more when playing high definition video. That being said, it’s a bit overpowered to be used as a simple HTPC card; there are plenty of more affordable, lower rung GeForce and Radeon models that can do just as well in this regard.

Our thanks to ZOTAC for the GeForce GT 640 ZONE Edition video card sample.

* * *

Articles of Related Interest
SPCR’s 2012 Graphics Card/Cooler Test System

ASUS GeForce GTX 680 DirectCU II OC

Sapphire HD 7750 Ultimate Edition

ASUS DirectCU & AMD Radeon HD 6850 Graphics Cards

AMD Radeon HD 6570 & 6670 Budget GPUs

Arctic Cooling Accelero Xtreme Plus GPU Cooler

* * *

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SPCR forums.

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