Sensor and Performance

The ASUS ROG Harpe Ace is equipped with the ROG AimPoint. According to specifications, the AimPoint is capable of up to 36,000 CPI, as well as a maximum tracking speed of 650 IPS, which equals 16.51 m/s. I believe the AimPoint to be a PAW3395 variant. Out of the box, four pre-defined CPI steps are available: 400, 800, 1600, and 3200.

CPI Accuracy

"CPI" (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, there is no deviation at all, which is a perfect 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 without special equipment, it is done by comparison with a control subject that has been determined to have consistent and low motion delay. In this case, the control subject is a Logitech G403, whose PMW3366 sensor has no visible smoothing across the entire CPI range. Note that the G403 is moved first and thus receives a slight head start.

Testing is restricted to 2.4 GHz mode as Bluetooth is not suitable for non-casual gaming applications.

Wired testing

First, I'm looking at two xCounts plots—generated at 1600 and 36,000 CPI—to quickly gauge whether there is any smoothing, which would be indicated by any visible "kinks." As you can see, no such kinks are on display in either plot, suggesting there is no smoothing present. We can also see very low SPI timing jitter, no doubt owing to hardware MotionSync.


In order to determine motion delay, I'm looking at xSum plots generated at 1600 and 36,000 CPI. The line further to the left denotes the sensor with less motion delay. There is no motion delay differential at either step.

Wireless testing

Upon switching to wireless, we can see SPI timing loosening across the board.


I'm again looking at plots generated at 1600 and 36,000 CPI. Both 1600 and 36,000 CPI show a motion delay differential of at most 1 ms.

Speed-related Accuracy Variance (SRAV)

What people typically mean when they talk about "acceleration" is speed-related accuracy variance (SRAV). It's not about the mouse having a set amount of inherent positive or negative acceleration, but rather 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 (PCS) 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), at which no sign of the sensor malfunctioning can be observed.

Polling Rate Stability

Considering the Harpe Ace 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 of the available polling rate settings (125, 250, 500, and 1000 Hz) look and perform fine. 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. I'm unable to detect any 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 Harpe Ace at a lower polling rate can have the benefit of extending battery life. All available polling rates look and perform just fine.

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. 18,000 CPI shows major jitter, which is amplified to excessive levels at 36,000 CPI. This is in line with what to expect from a sensor lacking smoothing entirely. Lastly, there is no sensor lens movement.

Lift-off Distance

The Harpe Ace offers multiple ways of adjusting LOD: several pre-calibrated surface options, two pre-defined LOD levels (high/low), and manual calibration. By default, the "no calibration" preset is active, which has the sensor not track at a height of 1 DVD if set to "low." If set to "high," the sensor tracks 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). Furthermore, several pre-calibrated surfaces are available to choose from, which then can be fine-tuned manually by adjusting the high/low-selection. Performing a manual calibration may lower LOD beyond the default. In my case, doing so resulted in an LOD below 1 DVD.

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.

In wired mode, click latency has been measured to be roughly 0.4 ms, with standard deviation being 0.21 ms. In wireless mode, click latency has been measured to be roughly 0.8 ms, with standard deviation being 0.37 ms.

The main button switches were measured to be running at 1.91 V. I'm not aware of the voltage specifications of the ROG Micro Switches, but this value seems rather low to me.