Sensor and Performance

The Endgame Gear XM2we is equipped with the PixArt PAW3370. According to specifications, the 3370 is capable of up to 19,000 CPI, as well as a maximum tracking speed of 400 IPS, which equals 10.16 m/s. Out of the box, four pre-defined CPI steps are available: 400, 800, 1600, and 3200.

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 consistently positive and moderately high, 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 without special equipment, it is done by comparison with a control subject that has been determined to have consistent and low motion delay. In this case, the control subject is a Logitech G403, whose PMW3366 sensor has no visible smoothing across the entire CPI range. Note that the G403 is moved first and thus receives a slight head start.

Wired testing

First, I'm looking at two xCounts plots—generated at 1600 and 19,000 CPI—to quickly gauge whether there is any smoothing, which would be indicated by any visible "kinks." Neither plot shows any kinks, indicating there not being any smoothing.


In order to determine motion delay, I'm looking at xSum plots generated at 1600, 19,000 CPI, and 19,000 CPI with ripple control enabled. The line further to the left denotes the sensor with less motion delay. Both 1600 and 19,000 CPI without ripple control show no motion delay differential. With ripple control enabled at 19,000 CPI, a motion delay differential of 2 ms can be measured.

Wireless testing

Not much changes when running the XM2we in wireless mode as SPI timing jitter and general tracking are virtually on the same level as when wired. Occasionally however, outliers show up, which appear to be related to polling:


I'm unable to reproduce this behavior consistently.


Once again, 1600, 19,000 CPI, and 19,000 CPI with ripple control enabled are tested. Both 1600 and 19,000 CPI without ripple control show a motion delay differential of less than 1 ms. At 19,000 CPI with ripple control enabled, a motion delay differential of roughly 3 ms can be measured.

Speed-related Accuracy Variance (SRAV)

What people typically mean when they talk about "acceleration" is speed-related accuracy variance (SRAV for short). It's not about the mouse having a set amount of inherent positive or negative acceleration, but whether the cursor travels the same virtual 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, confirming that the 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 and results in no observable sign of the sensor malfunctioning.

Polling Rate Stability

Considering the XM2we is usable as a regular wired mouse as well, I'll be testing polling rate stability for both wired and wireless use.

Wired testing


All of the available polling rates (125, 250, 500, or 1000 Hz) look and perform fine.

Wireless testing
For wired mice, polling rate stability merely concerns the wired connection between the mouse (SPI communication) and the USB. For wireless mice, another device that needs to be kept in sync between the first two is added to the mix: the wireless dongle/wireless receiver. I'm unable to measure all stages of the entire end-to-end signal chain individually, so testing polling-rate stability at the endpoint (the USB) has to suffice here.


First, I'm testing whether SPI, wireless, and USB communication are synchronized. Any of these being out of sync would be indicated by at least one 2 ms report, which would be the result of any desynchronization drift accumulated over time. I'm unable to detect any periodic off-period polls that would be indicative of a desynchronization drift.



Second, I'm testing the general polling-rate stability of the individual polling rates in wireless mode. Running the XM2we at a lower polling rate can have the benefit of extending battery life. 125, 250, and 500 Hz exhibit periodic outliers, leaving 1000 Hz as the only fully stable polling rate.

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 CPI. 19,000 CPI without ripple control displays major jitter, which is lessened to moderate levels upon enabling ripple control. Lastly, there is no sensor lens movement.

Lift-off Distance

The XM2we offers two pre-defined LOD levels. At the "1 mm" setting, the sensor does not track at a height of 1 DVD (<1.2 mm). Using the "2 mm" setting, the sensor does track at a height of 1 DVD (1.2 mm<x<2.4 mm, with x being LOD height), but not at a height of 2 DVDs. 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, debouncing is required to avoid double clicks, slam-clicks, or other unintended effects of switch bouncing. Debouncing typically adds a delay, which, along with any potential processing delay, shall be referred to as click latency. In order to measure click latency, the mouse has been interfaced with an NVIDIA LDAT (Latency Display Analysis Tool). Many thanks go to NVIDIA for providing an LDAT device. More specifically, the LDAT measures the time between the electrical activation of the left main button and the OS receiving the button-down message. Unless noted otherwise, the values presented in the graph refer to the lowest click latency possible on the mouse in question. If a comparison mouse is capable of both wired and wireless operation, only the result for wireless (2.4 GHz) operation will be listed.

Since I couldn't get click latency measurement working in wired mode, testing is restricted to wireless. In wireless mode and using a debounce time of 0/1 ms, click latency has been measured to be roughly 3.9 ms, with standard deviation being 0.46 ms. In wireless mode and using a debounce time of 4 ms, click latency has been measured to be roughly 6.9 ms, with standard deviation being 0.46 ms. Scaling is linear.

Much like on other mice using the CX52850 MCU, latency for the first click after five seconds of both sensor and button inactivity is increased. More specifically, the first click will be extended to a latency value equal to roughly 9 ms, provided the set debounce time results in an effective latency equal to or lower than that.