Sensor and Performance

The EVGA X12 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, five pre-defined CPI steps are available: 800, 1600, 3200, 6400, and 16,000.

All testing was done on the latest firmware (1.86). As such, results obtained on earlier firmware versions may differ from those presented hereafter. Unless noted otherwise, I'll exclusively test the X12 at 1000 Hz on this page. This is done both to provide the full picture and establish a baseline for testing polling rates higher than 1000 Hz, which follows on the next page.

CPI Accuracy

"CPI" (short for counts per inch) describes the number 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 differ 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 exclusively positive, highly consistent, and decently low, which is a good result overall. In order to account for the measured deviation, adjusted steps of 400, 800, 1550, 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 among 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 16,000 CPI to quickly gauge whether there is any smoothing, which would be indicated by any visible "kinks." Typically, the 16,000 CPI plot would show such kinks given the 3389 usually has 32 frames of smoothing at and above 1900 CPI, which is then doubled at 6000 CPI and 11,300 CPI. As you can see, this is the case here, although the kinks are just barely visible. This confirms that the 3389 in the X12 is performing as expected. We can also see fairly low SPI timing jitter.


In order to determine motion delay, I'm looking at xSum plots generated at 1600 and 16,000 CPI. The line further to the left denotes the sensor with less motion delay. At 1600 CPI, the X12 is slightly ahead. 3200 CPI shows a motion delay differential of roughly 2.5 ms as the first level of smoothing is applied. 16,000 CPI has the second level of smoothing applied and shows a differential of roughly 12 ms. This is in line with what to expect from a 3389. Quite curious, however, is that framerate transitions show up in both xCount and xSum as long as smoothing is present, as seen below:


The first framerate transition in particular has a direct impact on motion delay, which increases past that point. I'm unable to provide an explanation for this behavior.

Speed-related Accuracy Variance (SRAV)

What people typically mean when they talk about "acceleration" is speed-related accuracy variance (or SRAV for short). 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 5 m/s (which is within the proclaimed PCS range), at which no sign of the sensor malfunctioning can be observed.

Polling-rate Stability

On a previous firmware, all of the available polling rates (125, 250, 500, and 1000 Hz) suffered from periodic bursts of off-period polls. I've received a firmware update from EVGA which corrects this for all polling rates but 125 Hz. With RGB lighting enabled, polling stability deteriorates slightly.

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 the first level of smoothing applied. 16,000 CPI has more smoothing and jitter, but compared to other 3389 implementations, the latter is surprisingly well-controlled. Lastly, there is no sensor lens movement.

Lift-off Distance

The X12 does not offer any pre-defined LOD levels to choose from right from the get-go. Instead, one has to perform a surface calibration first, which may lower the LOD beyond the default level, which is below 1 DVD (<1.2 mm) already. From there, one can choose between four different preference settings: office, universal gaming, FPS gaming, and custom. The latter allows one to choose between three non-discrete levels: High, Low, and Xtreme Low. Set to "High," 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). Set to "Low," the sensor does not track at a height of 1 DVD (<1.2 mm), which continues to be the case at the "Xtreme Low" setting. Keep in mind that LOD may vary slightly depending on the mousing surface (pad) it is being used on.

Click Latency

In most computer mice, mechanical switches are being used for the main buttons, which require debouncing in order to avoid unintended double clicks. Debouncing typically adds a delay (along with any potential processing delay), which shall be referred to as click latency. As there is no way to measure said delay directly outside of using a USB analyzer, it has to be done by comparing it to a control subject, which in this case is the ASUS ROG Chakram Core. The test setup involves wiring the NO pin of one of the main button switches of the test subject to one of the control subject, and qsxcv's program is used to measure the relative delay between them. Doing so is only possible if the devices in question are plugged into the PC through a wired connection. The Zaunkoenig M2K has been posited as the baseline for being within 0.1 ms of the possible minimum click latency of a high-speed device and within 0.2 ms of a hypothetical absolute minimum. As such, the resulting values may be considered quasi-absolute.

Using the default 1000 Hz polling rate, click latency has been measured to be roughly +5.0 ms, with standard deviation being 0.40 ms. At a polling rate of 8000 Hz, click latency has been measured to be roughly +4.5 ms, with standard deviation being 0.31 ms.