Sensor and Performance

The Glorious Model O Wireless is equipped with the BAMF sensor, which I believe to be based on 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.

All testing was done on the latest firmware. As such, results obtained on earlier firmware versions may differ from those presented hereafter.

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 somewhat significant. An average result overall. In order to account for the measured deviation, adjusted steps of 400, 800, 1550, and 3100 CPI have been used for testing. Due to the BAMF supporting increments of 10 CPI up to the 10,000 CPI mark, even finer adjustments would be possible.

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 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." As you can see, such kinks are plainly on display in the second plot, which confirms that there is smoothing. In order to determine the precise amount, we'll have to turn to xSum testing. On a cursory note, SPI timing jitter is quite low.



In order to determine motion delay, I'm looking at xSum plots generated at 1600 (first row) and 19,000 CPI. The line further to the left denotes the sensor with less motion delay. What can be observed here is a behavior I've seen on several 3335 implementations. Basically, latency is greatest upon initiating motion and continually decreases from there until a minimum is reached. At the onset of the plotted motion, the motion delay differential is 3.5 ms, whereas at the end of it, it is within 0.5 ms. The most truthful way to present this data is by giving a range; i.e., 0.5–3.5 ms. In short, delay will be higher for the first ~100 ms of any motion, but after that, it'll bottom out to the minimum value. This behavior is consistent across the entire CPI range, although the relative motion delay differential will decrease as the absolute amount of delay increases due to added smoothing. At 19,000 CPI, the minimum motion delay sits at 4 ms. Since smoothing barely ramps up across the CPI range, I'm unable to precisely determine any transition points.

Wireless testing

Not much changes when running the Model O Wireless in wireless mode. As expected, 19,000 CPI still shows the same kinks indicative of smoothing, and SPI timing jitter and general tracking are virtually on the same level as when wired.



Keeping the motion delay differential in wired mode established above in mind, I can measure a wireless delay of roughly 1–1.5 ms. Curiously, the absolute level of smoothing is generally increased in wireless mode, as evidenced by the 19,000 CPI plot.

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 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

Considering the Model O Wireless 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 four of the available polling rates (125/250/500/1000 Hz) look nice and stable. Polling stability is unaffected by any of the available RGB lighting effects.

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. Aside from the odd polling outlier (not pictured), I'm unable to detect 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 Model O Wireless at a lower polling rate can have the benefit of extending battery life. As you can see, all four available polling rates look perfectly 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. Since there have been claims that the Model O Wireless indeed suffers from angle snapping, I've conducted an additional test pictured on the right. In short, I've found nothing that would corroborate such claims. No jitter is visible at 1600 CPI. At 8000 CPI, minor jitter can be observed, which is amplified at 14,000 CPI. Finally, 19,000 CPI shows major jitter. Lastly, there is no sensor lens movement.

Lift-off Distance

The Model O Wireless offers two pre-defined LOD levels to choose from. At the default "1 mm" setting, the sensor does not track at a height of 1 DVD (<1.2 mm). This does not change when choosing the "2 mm" setting, so this option may not be functional. Keep in mind that LOD may vary slightly depending on the mousing surface (pad) it is being 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. In wired mode and using the 2 ms debounce time setting, click latency has been measured to be roughly +1.9 ms when compared to the SteelSeries Ikari, which is considered as the baseline with 0 ms. Coupled with the measured wireless delay of 1.0–1.5 ms, click latency in wireless mode sits at roughly +2.9–3.4 ms. Lowering debounce time to 0 ms will reduce click latency accordingly. Please keep in mind that the measured value is not the absolute click latency. Comparison data comes from this thread as well as my own testing, using qsxcv's program.

The main button switches were measured to be running at 1.97 V. Since the same switches are running at 5 V in the regular wired Model O, I believe these to be running below specifications in the Model O Wireless. This would still hold true if the logic were running at 3.3 V instead. This isn't unusual on wireless mice and typically done to prolong battery life. On the other hand, operating switches below their voltage specifications can shorten their life expectancy.