Sensor and Performance

The XPG PRIMER is equipped with the PixArt PMW3360. According to specifications, the 3360 is capable of up to 12,000 CPI, as well as a maximum tracking speed of 250 IPS, which equals 6.35 m/s. Out of the box, six pre-defined CPI steps are available: 400, 800, 1600, 3200, 6400, and 12,000 CPI.

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 actual CPI not matching nominal 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 average, and all steps are consistently below target. An average result overall, but good enough considering there's no way to adjust CPI in software as of now.

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.


First, I'm looking at two xCounts plots—generated at 1600 and 3200 CPI—to quickly gauge whether any smoothing is present, which would be indicated by any visible "kinks." As you can see, no such kinks can be observed at 1600 CPI, while it's plainly visible at 3200 CPI. This is in line with what to expect from a 3360. We can also see that SPI timing jitter levels are remarkably low.


Let us take a look at three additional xSum plots, generated at 1600, 3200, and 12,000 CPI. The line further to the left denotes the sensor with less motion delay. At 1600 CPI, motion delay is identical. Both 3200 CPI and 12,000 CPI show a motion delay differential of roughly 3.5 ms, which is expected as the PMW3360 has 32 frames of smoothing at and above 2100 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 4.0 m/s (which is within the proclaimed PCS range), at which no sign of the sensor malfunctioning can be observed.

Polling Rate Stability

There is but a single polling rate available: 1000 Hz. Thankfully, this setting looks nice and stable.

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 400, 1600 CPI, and 3200 CPI, the latter of which already has smoothing applied, which takes care of the jitter. At 12,000 CPI, jitter is high but not excessive. Lastly, no sensor lens rattle can be observed.

Lift-off Distance

The PRIMER does not support LOD adjustment. This is unfortunate as the 3360 would be fully capable of it. At the only default setting, the sensor does not track at a height of 1 DVD (<1.2 mm). Keep in mind that LOD may vary slightly depending on the mousing surface (pad) it is being used on.

Click Latency

For some reason, I'm unable to get any click latency readings using my usual method. I suspect it's due to the used MCU. Using the less reliable bump test, I can measure a click latency in the range of +13–15 ms relative to the SteelSeries Ikari, which is considered as the baseline.