Sensor and Performance

The Chakram 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, four pre-defined CPI steps are available: 400, 800, 1600, and 3200.

CPI Accuracy

"CPI" (short for counts per inch) describes the amount of counts registered by the mouse if it is moved exactly one 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 as well.


I've restricted my testing to the four most common CPI steps, which are 400, 800, 1600, and 3200. As you can see, the steps are spot on for the most part, which is 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.

All wireless testing was done using the regular 2.4 GHz wireless mode as I'm unable to test the Bluetooth mode due to the lack of a Bluetooth-enabled device. That having been said, the lowered polling rate as well as the properties of the transfer protocol make Bluetooth mode unsuitable for anything that isn't office usage anyway.

Wired Testing

First, I'm looking at two xCount plots. Typically, any "kinks" showing up within the plot would be indicative of sensor smoothing present at that CPI step. As you can see, only the second plot shows such kinks. We'll have to take a look at the xSum plots to determine at which step the smoothing kicks in then. In any case, tracking is quite clean, with only minor SPI timing jitter to speak of.


Here, I'm looking at xSum plots generated at 1600, 11,700, and 16,000 CPI. The line further to the left denotes the sensor with less motion delay. At 1600 CPI, motion delay is identical; at 11,700 CPI, motion delay is 2 ms; and at 16,000 CPI, motion delay is still 2 ms. There may be some very minor smoothing even before the 11,700 CPI step (1 ms), but it's difficult to say for sure due to the xCount test being inconclusive. Either way, smoothing is minor across the board and only kicks in late to any substantial degree.

Wireless Testing

Tracking quality takes somewhat of a hit in wireless mode. Both plots show increased SPI timing jitter and several dropped polls, with the effects being more pronounced in the 16,000 CPI plot. My findings suggest that the frequency of dropped polls increases as the physical speed the mouse is moved with increases.


Testing is again done at 1600, 11,700, and 16,000 CPI. Keeping the motion delay differential established above in mind, I can measure a wireless delay of roughly 1.5 ms.

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 m/s (which is within the proclaimed PCS range), at which speed no sign of the sensor malfunctioning can be observed. We can see the same visible kinks on the xCount plots above, however.

Polling Rate Stability

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 communications are synchronized. Any of these not being in sync would be indicated by at least one 2 ms report being visible, which would be the result of any desynchronization drift accumulated over time. As you can see, despite some polling outliers, no 2 ms reports are visible, which suggests that the polling of the entire signal chain is in sync.



Second, I'm testing general polling-rate stability of the individual polling rates in wireless mode. Running the Chakram at a lower polling rate can have the benefit of extending battery life. 125 Hz, 250 Hz, and 1000 Hz all show higher than average variance, but still within acceptable limits for a wireless device. 500 Hz, on the other hand, appears to be broken in some way and should be avoided.

Paint Test

This test (done in wired mode) is used to indicate any potential issues with angle snapping (non-native straightening of linear motion) and jitter, along with any sensor lens rattle. I'm testing 1600 CPI as a general use baseline; 11,600 CPI as the last step without smoothing; 11,700 CPI as the first smoothed step; and 16,000 CPI as the highest CPI step. As you can see, no issues with angle snapping can be observed at any CPI step. No jitter is visible at 1600 CPI, but there is moderate to high jitter at 5000 CPI, which decreases quite significantly at 11,700 CPI, where smoothing is first applied. 16,000 CPI doesn't look much different. Overall jitter levels are very reasonable, especially compared to a more smoothing-heavy sensor, such as the 3389. Lastly, there is no sensor lens rattle.

Lift-off Distance

The Chakram offers two pre-defined LOD values to choose from. On the "low" setting, the sensor does not track at a height of 1 DVD. On the "high" setting, it does track at a height of 1 DVD, but not at a height of 2 DVDs. Keep in mind that LOD may vary slightly depending on the mousing surface (pad) it is used on.

Click Latency

Since mechanical switches are being used for the buttons in most computer mice, debouncing is required 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, it has to be done by comparing it to a control subject, which in this case is the Logitech G203. Click latency in wired mode has been measured to be roughly +3.2 ms when compared to the SteelSeries Ikari, which is considered as the baseline with 0 ms. For whatever reason, I was unable to measure anything in wireless mode. However, I can report that the main button switches still run at the specified 3.3 V in wireless mode. Comparison data comes from this thread as well as my own testing, using qsxcv's program.