Sensor and Performance

The Razer Viper Ultimate is equipped with the Focus+. According to specifications, the Focus+ is capable of up to 20,000 CPI as well as a maximum tracking speed of 650 IPS, which equals 16.51 m/s. "Focus+" is Razer's name for the PAW3399, which has been co-developed by PixArt and Razer. Although the package looks identical to the PMW3360 or 3389, the 3399 is indeed wholly different on the silicon level (and not related to the PAW3335 either). Out of the box, there are five pre-defined CPI steps available: 400, 800, 1600, 2400, and 3200 CPI.

Disclaimer: All of my testing has been done with firmware that are not yet publicly available. That having been said, the expected difference between the not-yet-available firmware and the available firmware should be minimal for the vast majority of use cases.  

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.


I've restricted my testing to the four most common CPI steps, which are 400, 800, 1600, and 3200. As you can see, the deviation is decently low (albeit not consistent), which is a 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.

Since the Viper Ultimate can be used in both wired and wireless mode, I'll be testing it in both modes against the G403. For the wireless test I've decided to refrain from pitting the Viper Ultimate up against another wireless mouse (such as the Logitech G Pro Wireless), as using a wired mouse ensures that there is no additional source of possible wireless interference affecting the results.

Wired testing

First, I'm looking at two xCounts plots. Theoretically, any "kinks" visible at framerate transition points would be indicative of sensor smoothing. Since the Focus+ uses a self-adjusting framerate instead of pre-defined framerate levels no such kinks would show up either way, which makes this test non-indicative of smoothing. However, the tight grouping in the 400 CPI plot in particular is noteworthy as it points towards timing consistency.


Let us take a look at xSum plots then. As you can see, the two mice are only separated by margin of error at the tested CPI steps of 400 and 1600 CPI. At 20,000 CPI there appears to be a delay of around 1.5–2 ms, although I'm fairly confident that it is not caused by smoothing.

Wireless testing

Now that we have established the expected motion delay of the Focus+ at the tested CPI steps in wired mode, we can test for timing consistency and wireless delay in wireless mode. The xCount plots once again are notably tight. It is reasonable to assume that the high level of timing consistency demonstrated here is due to Razer's advertised "MotionSync" feature of the Focus+.


Onto the xSum plots, again generated at 400, 1600, and 20,000 CPI. Keeping the results from the wired tests in mind, I've been able to measure an average wireless delay of around 1 ms. This was with all wireless devices in my proximity turned off and the mouse within a distance of less than 10 cm to the wireless receiver. For what it's worth, I also performed the same tests with all wireless devices in my proximity enabled and got the same results.

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. The proclaimed PCS of the Focus+ is high enough that it becomes physically impossible to exceed it. I've only managed to hit a measly 4.5 m/s (which is within the proclaimed PCS range), at which speed no sign of the sensor malfunctioning can be observed.

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 communication 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, no such drift can be observed, which confirms that the polling of the entire signal chain is in sync. This has been verified even during extended periods (120+ seconds) of monitoring.


Second, I'm testing general polling-rate stability of the individual polling rates in wireless mode. Running the Viper Ultimate at a lower polling rate can have the benefit of extending battery life. While 125 Hz and 1000 Hz run stable and as expected, 500 Hz exhibits weird issues like these:


I was unable to reproduce these issues consistently, but for now, I'd recommend using either 125 Hz or 1000 Hz just to be sure. Furthermore, Razer has been unable to reproduce this behavior, so it may in fact be limited to my particular case.

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. As expected from a sensor without any smoothing, the higher CPI steps exhibit jitter and ripple. I'd consider the level of jitter at the highest (20,000) CPI step unusably high. That having been said, I struggle to see practical applications of such high CPI anyway. Furthermore, there is no sensor lens rattle present.

Lift-off Distance

The Razer Viper Ultimate offers a wider range of possible LOD adjustment than most mice. One can either keep the default automatic calibration enabled or choose to run a manual calibration. When using the former option, LOD can be set to 1 mm, 2 mm, or 3 mm. Additionally, Asymmetric Cut-off can be enabled, which allows for a higher lift-off distance while keeping the landing distance low. At a height of 1 DVD, the Viper Ultimate does not track on the 1 mm setting, but it does on the 2 mm and 3 mm settings. At a height of two DVDs, it tracks on none of the LOD settings. It should be kept in mind, however, that LOD may vary slightly depending on the mousing surface (pad) it is being used on.

Click Latency

Most computer (and gaming) mice use mechanical switches for the buttons. Mechanical switches need debouncing in order to function as intended, which can add a delay, commonly referred to as click latency. Mechanical switches are used on wireless mice too, but operated at a lower voltage in order to save battery life. The lower operating voltage can lead to accelerated degradation (corrosion) of the mechanical parts of the switch, which in turn shortens the lifespan and possibly introduces unintended double clicks. For this reason Razer has opted to use optical switches for the main buttons in the Viper Ultimate. The main benefit of optical switches is the fact that they do not require debouncing, which not only keeps click latency low but also circumvents the issue described above entirely.

Unfortunately, this also means that I'm unable to conduct my usual click latency testing. Theoretically, the usage of optical switches instead of mechanical ones should result in the click latency being identical with whatever processing delay the mouse has, as there is no debounce delay at all. Testing done by using the "bump method" indeed shows accordingly low latency results, but due to that test not being reliable enough I decided not to include those numbers here. You can rest assured, however, that click latency is very low.