In general terms, polling rate can be described as the rate at which the data generated by the mouse is transmitted from the mouse to the PC via USB. Polling rate is measured in Hz; i.e., the number of times per second. The higher the polling rate (i.e., the lower the polling interval), the more frequently the cursor position and any other input events (button inputs) are updated, resulting in improved positional accuracy and generally reduced latency. At 1000 Hz, the polling interval is 1 ms, meaning the PC receives a new update every 1 ms. At 2000 Hz, the interval is 0.5 ms, and at 4000 Hz, the interval is 0.250 ms.
4000 Hz: The Technology and How to Use It
Wired mice natively capable of polling rates in excess of 1000 Hz have first found some adoption in 2021. For wireless mice, the only mouse at least claimed to be capable of wireless 2000 Hz polling was the Corsair Sabre RGB Pro Wireless, although that claim turned out to be false. With the HyperPolling Wireless Dongle, any compatible Razer mouse is effectively upgraded into a high-speed device, which, unlike full-speed devices, are natively capable of polling rates higher than 1000 Hz. Only mice explicitly listed as compatible by Razer will work with the HyperPolling Wireless Dongle, as both the firmware and hardware (sensor in particular) need to be capable of fully supporting 4000 Hz wireless polling.
Within Synapse, polling rates of 125, 500, 1000, 2000, or 4000 Hz are available. However, it is important to note that those values merely denote the maximum applicable polling rate. If the mouse isn't physically moved enough to generate a sufficient number of motion events (for 4000 Hz at least 4000 pixels worth of motion per second), less updates will be transmitted, resulting in a lower effective polling rate. Accordingly, it is strongly recommended to use a sufficiently high CPI step in conjunction with the HyperPolling Wireless Dongle. I would advise using at least 1600 CPI, and possibly even higher steps depending on one's effective in-game sensitivity (turn circumference). The higher the turn circumference, the more physical motion is typically generated, and thus lower CPI is required to saturate the polling rate. Conversely, the lower the turn circumference, the less physical motion is generated, and thus higher CPI is required to saturate the polling rate. On the Viper V2 Pro, the entire CPI range may be used without any motion delay penalty, as no smoothing is applied at any point. Other Razer wireless mice may behave differently however, which is why Razer may want to give users control of the amount of smoothing applied in conjunction with the HyperPolling Wireless Dongle in the future. Unlike on the Viper 8K, the set polling rate does affect click latency when using the HyperPolling Wireless Dongle. Hence, in order to get the lowest possible click latency, 4000 Hz must be used.
In order to get the full benefit out of 4000 Hz polling, certain conditions need to be met. First, it is recommended to have a sufficiently powerful CPU; i.e., one with six physical cores and appropriately high IPC at the least. Second, the OS has to be capable of interrupt moderation of 125 μs or lower. This is true of Windows 8 or higher, where interrupt moderation on XHCI will typically be 50 μs, but not of Windows 7 and lower, where interrupt moderation is never below 1 ms unless changed manually, which isn't easily done. On EHCI, interrupt moderation can be expected to be 125 μs on Windows 8 or higher, which is sufficient but not optimal. Third, it is therefore recommended to plug the HyperPolling Wireless Dongle into a USB 3.x port in XHCI mode. Any USB 3.x ports forced into EHCI will behave similarly to a native USB 2.x port. As a general rule of thumb, one should be using a USB port native to the CPU and not connect any other high-polling devices to a port of the same hub. Even if all of these conditions are met, actual polling stability during higher workloads will further depend on general system and OS health. As such, it is recommended to use a reasonably optimized OS installation without bloat in conjunction with the HyperPolling Wireless Dongle.
Performance Testing: Sensor
In this section, I'll be testing general tracking, polling stability, and motion delay for both 2000 and 4000 Hz. Polling and tracking were tested at 1600 CPI, whereas motion delay has been tested at 3200 CPI. Please note that the G403 is moved first and thus receives a head start of roughly 0.2 ms.
2000 Hz:
Owing to sensor-level MotionSync, count distribution is very tight. The Viper V2 Pro averages exactly 0.5 ms and is ahead of the G403 by roughly 0.2 ms.
4000 Hz:
Despite MotionSync still being active, count distribution is slightly looser. The Viper V2 Pro averages exactly 0.25 ms and is ahead of the G403 by roughly 0.5 ms.
Performance Testing: Click Latency
Most gaming mice use mechanical switches for their buttons. By wiring the switches of the test subject together with the switches of a control subject, I'm able to measure click latency very accurately; i.e., standard error of around 0.05 ms. However, this method is not applicable to mice with non-mechanical switches and wireless-only mice in general. As such, other methods ought to be employed, one of which is NVIDIA's Latency Display Analysis Tool (LDAT). The LDAT allows me to measure the entire end-to-end latency between the mouse click and photon transition on the monitor. By establishing the relative difference to a control subject, I'm then able to provide values I consider sufficiently accurate; i.e., standard error of around 0.2 ms. The Razer Viper 8K has been posited as the baseline for being within 0.1 ms of a hypothetical absolute minimum. Many thanks go to NVIDIA for providing me an LDAT v2 device.
At the default 1000 Hz, click latency has been measured to be roughly +2.1 ms on the Viper V2 Pro, with standard deviation being 2.2 ms. At 2000 Hz, click latency decreases by roughly 0.4 ms, and standard deviation is 2.6 ms. At 4000 Hz, click latency decreases by another 0.3 ms, and standard deviation is 2.6 ms. Keep in mind that due to the indicated value being neither the absolute click latency nor the measured end-to-end-latency, standard deviation ends up looking disproportionally large. Comparison data comes from my own testing and has been exclusively gathered with the LDAT.
Subjective Evaluation
Of course, the performance metrics obtained through empirical testing are just one side of the coin. The more pressing question is whether 4000 Hz is at all noticeable in games, and if so, to which degree.
To properly answer this question, note that someone being unable to notice something does not mean it isn't there objectively, or does not provide an objective advantage. The latter is most definitely true of 4000 Hz polling with the HyperPolling Wireless Dongle, so the matter shifts towards whether said advantage is meaningful and thus noticeable one way or another. That said, playing on a 165 Hz monitor at typically 200 FPS or more, I indeed struggled to notice a difference in terms of latency compared to 1000 Hz. As explained above, saturating the full 4000 Hz polling rate takes quite a bit of mouse movement, and thus isn't typically reached all the time anyway, so most of the time, the benefit in terms of latency compared to 1000 Hz is around 0.5 ms, which is well below the sensory capabilities of the average human. The greatest effect of 4000 Hz may indeed not be observed in terms of absolute latency, but rather general positional accuracy and smoother cursor feel, more specifically in games requiring high precision in regards to click timing. Particularly games supporting sub-frame input will benefit to a greater degree from 4000 Hz, such as Overwatch or Diabotical with their respective settings enabled. Generally, in order to get any use out of 4000 Hz, I'd recommend using a strong CPU and a 240 Hz or even 360 Hz display. Slower panels will inevitably struggle to even display the granularity afforded by 4000 Hz polling. Those with weaker CPUs may experience worse input response simply due to the higher CPU cost, which means any advantage gained by 4000 Hz immediately cancels itself out.
When choosing between 2000 and 4000 Hz, 2000 Hz may indeed the most sensible choice. The gain in motion delay and click latency is much greater from 1000 to 2000 Hz than from 2000 to 4000 Hz, yet 4000 Hz will result in significantly lower battery life compared to 2000 Hz. Furthermore, most of the time 4000 Hz won't be saturated anyway unless high CPI (>3000) is used, so the actual benefit in terms of motion delay may be even smaller.
Appendix: List of Tested Games
As there is little reason to use 2000 or 4000 Hz in non-competitive games, I'll exclusively list games that are typically considered competitive. In order to only use 2000 or 4000 Hz in games in which it makes sense to do so, and to use 1000 Hz or less in others, one can use Synapse's ability to assign different polling-rate values to specific application profiles that are automatically applied depending on which application is currently running. Please note that a game running fine for me won't necessarily run fine for everyone, as it merely means it generally works well with 4000 Hz polling. Conversely, a game not working well at 4000 Hz on a specific system isn't generally incompatible with 4000 Hz polling.