Sensor and Performance

The Cooler Master MM720 is equipped with the PixArt PMW3389. According to specifications, the 3389 is capable of up to 16,000 CPI, as well as a maximum tracking speed of 400 IPS, which equals 10.16 m/s. Out of the box, seven pre-defined CPI steps are available: 400, 800, 1200, 1600, 3200, 6400, and 16,000 CPI.

All testing was done on the latest firmware. As such, results obtained on earlier firmware versions may differ from those presented hereafter.

CPI Accuracy

"CPI" (short for counts per inch) describes the amount of counts registered by the mouse if it is moved exactly an inch. There are several factors (firmware, mounting height of the sensor not meeting specifications, mouse feet thickness, mousing surface, among others) which may contribute to nominal CPI not matching actual CPI. It is impossible to always achieve a perfect match, but ideally, nominal and actual CPI should differ as little as possible. In this test, I'm determining whether this is the case or not. However, please keep in mind that said variance will still vary from unit to unit, so your mileage may vary.


I've restricted my testing to the four most common CPI steps, which are 400, 800, 1600, and 3200. As you can see, deviation is pretty low and exclusively negative. A good result overall. In order to account for the measured deviation, adjusted steps of 400, 800, 1600, and 3100 CPI have been used for testing.

Motion Delay

"Motion delay" encompasses all kinds of sensor lag. Any further sources of input delay will not be recorded in this test. The main thing I'll be looking for in this test is sensor smoothing, which describes an averaging of motion data across several capture frames in order to reduce jitter at higher CPI values, increasing motion delay along with it. The goal here is to have as little smoothing as possible. As there is no way to accurately measure motion delay absolutely, it can only be done by comparison with a control subject that has been determined to have the lowest possible motion delay. In this case the control subject is a G403, whose 3366 has no visible smoothing across the entire CPI range. Note that the G403 is moved first and thus receives a slight head start.


First, I'm looking at two xCounts plots—generated at 1600 and 3200 CPI—to quickly gauge whether there is any smoothing, which would be indicated by any visible "kinks." Typically, the 3200 CPI plot would show such "kinks" given the 3389 usually has 32 frames of smoothing at and above 1900 CPI, which amounts to an added motion delay of roughly 4 ms at the lowest possible speed. As you can see, this is the case here, although the kinks are just barely visible. We can also see rather high SPI timing jitter.


In order to determine motion delay, I'm looking at xSum plots generated at 1600 and 3200 CPI. The line further to the left denotes the sensor with less motion delay. At 1600 CPI, there is no difference in motion delay. At 3200 CPI, a motion delay differential of roughly 3.5 ms can be seen. This is in line with what to expect from a 3389, which has 32 frames of smoothing at and above 1900 CPI that is then doubled at 6000 CPI and 11300 CPI.

Speed-related Accuracy Variance (SRAV)

What people typically mean when they talk about "acceleration" is speed-related accuracy variance (or short SRAV). It's not about the mouse having a set amount of inherent positive or negative acceleration, but about the cursor not traveling the same distance if the mouse is moved the same physical distance at different speeds. The easiest way to test this is by comparison with a control subject that is known to have very low SRAV, which in this case is the G403. As you can see from the plot, no displacement between the two cursor paths can be observed, which confirms that SRAV is very low.

Perfect Control Speed

Perfect Control Speed (or PCS for short) is the maximum speed up to which the mouse and its sensor can be moved without the sensor malfunctioning in any way. I've only managed to hit a measly 4.5 m/s (which is within the proclaimed PCS range), at which no sign of the sensor malfunctioning can be observed.

Polling Rate Stability

All four available polling rates (125 Hz, 250 Hz, 500 Hz, and 1000 Hz) look nice and stable. Polling stability is unaffected by any RGB setting.

Paint Test

This test is used to indicate any potential issues with angle snapping (non-native straightening of linear motion) and jitter, along with any sensor lens rattle. As you can see, no issues with angle snapping can be observed. No jitter is visible at 1600 and 3200 CPI, the latter of which already has smoothing applied. 16,000 CPI shows high but not excessive jitter. Lastly, there is no sensor lens movement.

Lift-off Distance

The MM720 offers two pre-defined LOD levels to choose from. At the default "Low" setting, the sensor does not track at a height of 1 DVD (<1.2 mm). At the "High" setting, the sensor does track at a height of 1 DVD, but not at a height of 2 DVDs (1.2<x<2.4 mm; x=LOD height). Keep in mind that LOD may vary slightly depending on the mousing surface (pad) it is being used on.

Click Latency

Most computer (and gaming) mice use mechanical switches for the buttons. Mechanical switches need debouncing in order to function as intended, which can add a delay, commonly referred to as click latency. Much like recent Razer mice, the Viper Mini is using optical switches for the main buttons. Optical switches do not require any debouncing, hence no delay is added. Unfortunately, this also means I'm unable to conduct my usual click latency testing. Using the less accurate and reliable "bump test," I'm able to measure results that indicate a click latency of +8–10 ms relative to the SteelSeries Ikari, which acts as the baseline (+0.0 ms). Curiously, the button response time option within the software appears to be functional, as I do get consistently higher numbers when choosing a higher value. This is most certainly unexpected considering optical switches do not require debouncing, so I'm unsure where this delay is coming from, and why this option exists in the first place.