Sensor and Performance

The XPG Alpha is equipped with the PixArt PAW3335. According to specifications, the 3335 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, six pre-defined CPI steps are available: 400, 800, 1600, 3200, 6400, and 16,000.

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. Initially, deviation was all over the place, but I have been provided a firmware which fully fixes this, and deviation is minimal now. A very good result.

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 Alpha 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." Neither plot shows any kinks, indicating there not being smoothing. SPI timing jitter is very high and general tracking poor, however.


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. There is no motion delay differential at either CPI step, which confirms that there is no smoothing across the entire CPI range.

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 5 m/s, which is within the proclaimed PCS range and causes no observable sensor malfunction.

Polling Rate Stability

All of the four available polling rates (125, 250, 500, and 1000 Hz) look and perform fine as long as specific lighting effects are avoided:


The lighting effects in question are Rainbow Wave, Ripple, and Meteor.

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. 10,000 CPI already displays moderate jitter, and 16,000 CPI then shows major jitter. This is in line with what to expect from a sensor lacking smoothing entirely. Lastly, there is no lens movement.

Lift-off Distance

The Alpha offers two pre-defined LOD levels. Using the "2 mm" setting, the sensor does track at a height of 1 DVD, but not at a height of 2 DVDs (1.2 mm<x<2.4 mm, x being LOD height). This is still the case when using the "3 mm" 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, 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.

Using the default debounce time on press of 4 ms, click latency has been measured to be 4.6 ms, with standard deviation being 0.54 ms. Using a debounce time on press of 3 ms, click latency has been measured to be 3.7 ms, with standard deviation being 0.56 ms. Lastly, using a debounce time on press of 1 ms, click latency has been measured to be 1.5 ms, with standard deviation being 0.43 ms.