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How We Test Graphics Cards

Power Consumption And Noise Levels

Measuring Power Consumption

The time we've invested into measuring graphics card power consumption correctly is immense...but worth it. If you've already read The Math Behind GPU Power Consumption And PSUs, you already know why. If not, we suggest you check it out. 

Let's start small. Not every graphics card has an auxiliary power connector. Some get all of the power they needed from the motherboard using 3.3V and 12V rails. We measure those rails between the graphics card and motherboard through loops on the riser card.

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The voltage readings are also measured at the motherboard's 24-pin ATX connector, since that's where the rails begin their journey to the graphics card slot.

Values corresponding to auxiliary six- and eight-pin connectors are important as well. They can only be measured through their cables, right where they feed into the card. Since some cards with multiple connectors split them up to drive different power phases, it's sometimes necessary to use two amp clamps and probes, adding up to eight analog channels we monitor and log simultaneously.

All of this is implemented through two triggered oscilloscopes (master/slave) that act like a single eight-channel scope. Measurements are recorded through an active low-pass filter at the highest sampling rate possible in order to minimize aliasing effects and interfering noise as much as possible.

How Much Detail Do We Actually Need?

This is a good question that, unfortunately, is complicated to answer. We are sometimes criticized in our reviews for the way results are presented. Rightly so, perhaps. If you don't already have an in-depth understanding of the material, it's easy to overlook certain details or outright misinterpret them.

Recently, to make the data we're collecting more accessible, we increased the measurement intervals and introduced new software that's able to analyze short load spikes (and drops), checking them for plausibility. The resulting curve is a lot flatter, but also easier to interpret. Knowing that spikes can and do occur is important; they can be omitted, though, if it makes everything else we present more understandable.

Power Consumption
Test MethodContact-free DC Measurement at PCIe Slot (Using a Riser Card)Contact-free DC Measurement at External Auxiliary Power Supply CableDirect Voltage Measurement at Power Supply
Test Equipment2 x Rohde & Schwarz HMO 3054, 500MHz Digital Multi-Channel Oscilloscope with Storage Function4 x Rohde & Schwarz HZO50 Current Probe (1mA-30A, 100kHz, DC)4 x Rohde & Schwarz HZ355 (10:1 Probes, 500MHz)1 x Rohde & Schwarz HMC 8012 Digital Multimeter with Storage Function

Measuring Noise

We have another room we use for measuring noise, outside of our German lab. It's actually a room within a room, which helps us isolate against vibration and structure-borne noise (low sounds transmitted across the floor) to a large extent.

Especially when it comes to measuring the noise from quiet graphics cards, conventional sound level meters offer little more than optimistic estimates. They're definitely not accurate. Depending on the time of day and what's going on outside, our chamber makes it possible to record values as low as 20 dB(A) in a reproducible way.

Our previous-gen reference system serves as the foundation of our audio measurements. It lives on an open-air test bench that we made even quieter: without a graphics card and after insulating the power supply, it generates a base noise level of less than 23 dB(A) from 20 inches (50cm) away.

Each test run can be monitored from a separate control room. Just like everything else on this floor, the devices used in this room are exclusively fed via the DC power network.

Time and again we are asked why we present our results in dB(A) instead of Sone. The reason is simple: The definition of the so-called loudness in Sone is based on the definition of the volume level. A sine wave of 1kHz pitch at 40 dB (decibels) corresponds to a volume level of 40 Phon, which is, in turn, the base value for one Sone. If the sound feels twice as loud, the result is called two Sone. This seems practical, logical, and convenient enough. In practice, though, it can be difficult to apply.

Sone is only indicative of how loud an event can be perceived subjectively by an average human being. In that way, it's just another example of problematic psychoacoustics, and thus no better than its dB(A) counterpart. After all, nothing is more inaccurate than subjective impressions. Why? Test for yourself.

  • Take a radio and remember the value on its volume control scale.
  • Then, without looking at the scale, change the loudness to a value that feels twice as loud.
  • Next, (again without looking at the scale) return the loudness to what feels like half the current loudness.
  • Finally, compare the new position of the knob with its initial position. Unless you have a musician's trained ear, the result will probably surprise you. 

The only reasonably reliable method to determine loudness in Sone is the one described by E. Zwicker (implemented in DIN 45631:1991-03). However, it's somewhat complicated, and for quieter sounds below a value of one Phon (approximately 40 dB), it is still quite inaccurate. An unweighted dB measurement represents an actual level of sound pressure. It is thus a real measured value, rather than some event weighted using formulas. This is also why industry likes to use dB as a base unit. Unfortunately, dB isn't of much use to us either.

By instead using A-weighted dB values, we get filtered decibel results that are supposed to represent subjective physiological audio perception. Ironically, this brings us full circle. Sone and dB(A) are interpretations that do not stand for real measured values, but are based on assumptions. A result in dB(A) is an A-weighted sound pressure level based on a hearing threshold of 0 dB = 20 micro-Pascal. It allows for other factors, such as time weighting (fast or slow), to make the result mimic reality a little more closely. So where do we go from here?

The question remains: what exactly should be measured in practice? A-weighted sound pressure level or loudness? At least for now, we're using the former primarily for its better comparability and reproducibility. It's also worth mentioning that the equipment we're using has to be regularly and professionally calibrated to prevent deviations from casting doubt on our findings.

Simple Control Measurements

We can perform these control measurements in the lab at different distances to the object we're measuring. Of course, this is no substitute for an exact measurement, in spite of the calibrated microphone, good shielding, and similar analysis software as what we use in our measuring room. Still, it's good enough to give you an idea of what we're doing.

Setup For Measuring Noise Levels
MicrophoneNTI Audio M2211 (with Calibration File, Low Cut at 50Hz)
AmplifierSteinberg UR12 (with Phantom Power for Microphones) Creative X7
SoftwareSmaart v.7
Measuring ChamberCustom-Made Proprietary Measurement Chamber, 3.5 x 1.8 x 2.2m (LxDxH)
Measurement PositionPerpendicular to Center of Noise Source(s), Measurement Distance of 50cm
Measurement DataNoise Level in dB(A) (Slow), Real-time Frequency Analyzer (RTA)Graphical Frequency Spectrum of Noise

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  • DookieDraws
    Now that looks like a lab! Interesting read, Igor.
  • kwc813
    I like the article. That said, will they make THAT BENCH (or offshoot therof!) to sell? I've seen most out there, used more than a few and am tired of customizing. This would allow one to customize everything else and leave the platform just as it sits. Nice job!
  • zthomas
    love the glass box.. that system is high art.. the pics made my computer pic file.. to be posted elsewheres..
  • edlight
    I remember when there were comparisons of video quality and enhancements between ATI & nvidia, and results of an "HQV" DVD quality test for multiple cards. I've seen no mention that AMD, in their drivers since 7.5.1, have cut off detailed settings for video - you can't combine high sharpening and dynamic contrast, for instance. And they even now don't let you control the overall brightness, contrast, and gamma. They refer you to an MS thing in Win 7 where you set the brightness on your monitor. Well, ever monitor I've had set to 100% brightness still needed an adjustment at the video card to bring out the shadow detail.
    The enhancements are great - I run my R7 240 on the old drivers at 100% sharpening and dynamic contrast on, affect web video, etc. DVD's in Media Player Classic look like something much better, and 1080 looks 3D. It only works on certain players, though. It works for Flash mp4-AVC. I've always wondered if it would work on everything in Linux?
    I see that the cheapest nvidia with the latest enhancements is the GTX 1050. I'm wondering if it can sharpen the new YouTube? I have to use a Firefox plugin to force YouTube back to Flash to get the sharpening.
    I wish reviewers would get into that stuff, and for each card.
    I'd love it if reviewers of video cards would attend to these things.
  • Lucky_SLS
    Looking forward to the updated performance stats Igor. nicely done BTW
  • FormatC
    19288871 said:
    I like the article. That said, will they make THAT BENCH (or offshoot therof!) to sell? I've seen most out there, used more than a few and am tired of customizing. This would allow one to customize everything else and leave the platform just as it sits. Nice job!

    I dicussed it with Lian Li and they will sell the core version of the T70 (without the cover) and an optional upgrade kit with all other parts to close it. This can help to minimize the financial risk for Lian Li and the costs on the customers side. Everybody can buy what he really wish and not verybody needs the full program. This closed "Real World" table was my idea and I hope, the industry and also reviewers will like it too.

    The lab here was built over the years, but I was every time not really satisfied with all my benchtables. The power consumption thing I started in 2013, the infrared measurement in 2014/15 - long time before other sites copied this. The audio lab was built with the help of a good friend to realize the room-in-room concept. The location is nearly perfect and I spent a lot of time and money to finish it. I'm an audio-freak and measured in Germany tons of speakers and headsets too. This was really successful because we have only HiFi magazines with a lot of phrases for the so-called Golden Ears or mostly very flat and useless reviews on websites without any measuring. I tried to get the right balance between theory and real life, combined with understandable data and conclusions.

    And who I am? I moved to media ( + product development/consultations) in 2012 and was working the half of my life in the German industry (the last position as lead programmer and for quality control). That also means, that I'm significant over 50 and also know the basics of production processes and a lot of "secrets" behind the scene. For reviews it is not only interesting, how a product performs and where are possible issues - it is every time very fascinating and exciting to find also solutions or workarounds (like EVGAs thermal pad mod) and to communicate with the manufacturers. I used and I'm using a lot of time to visit factories and headquarters in Asia to get even more contacs and sources.

    I worked in the last years mostly for Tom's Hardware Germany - but I'm really happy, that we found new translators to bring my content also to the US/UK site. So I'm here and you must endure this now ;)

    have to use a Firefox plugin to force YouTube back to Flash to get the sharpening.
    At first - thx for your suggestions. I will think about it. But especially Flash is a dead horse and it is not worth to spend more time for it. HTML5 is a better standard and YT is moving all content step by step. Maybe, we can make sometime a video special to take a closer look at all this problems. For HTPC builds it is not uninteresting :)
  • zifn4b
    Dude! I use that wallpaper too. Excellent choice!
  • Olle P
    Great idea! ... but:
    Air cooling isn't desirable for a number of reasons. First, a large tower-style heat sink would block too much of the IR camera's view.
    Second, in a very small case like this, the cooler would dissipate so much waste heat that mainstream graphics cards with lower TDPs would be thermally overpowered, affecting the measurement results.
    I'd think the opposite way:
    * The heat generated by the CPU will be evacuated by the red fan. Shouldn't affect the graphics card one bit.
    * Some of the heat generated by the (high TDP) graphics card will impede the CPU cooling, which can affect CPU performance and thereby influence the test results. This is a viable part of real use and therefore a good thing to have in the test! It indirectly says if the graphics card will be more or less likely to require water cooling for the CPU to get the most performance out of it. (The main reason for having graphics coolers that blow as much of the heated air as possible directly out through the rear rather than just heating the case interior.)
  • Unolocogringo
    Hi Igor,
    Just wanted to say that I really enjoy the depth and precision of your reviews.
    Ive been a member of Toms Hardware since 96, and have watched the progression of reviews evolve over the years.
    Your latest addition should make your reviews much more in line with consumer experience, and I applaud you for your effort and insight.
  • junkeymonkey
    why a 850w PSU ?? would it not be better to use a 550w seeing how there recommended here in the forums for a nice gaming rig ??

    if asked here at toms that 850w is way too much overkill .