ScreenTune Boot Benchmarks
This page is the data behind ScreenTune’s boot optimization. Instead of community estimates, these numbers come from an on-device profiler that runs on every boot and timestamps each milestone against the unit’s own clock. We ran it on a stock baseline and on the full ScreenTune performance build using the same v74.00.324A CMU, back-to-back, so the only variable is the software.
The short version: CarPlay connects about 16–20 seconds sooner (typically ~16 s, up to ~20 s on a good boot), and the unit becomes fully responsive about 16 seconds sooner — every start.
How the data is collected
Section titled “How the data is collected”A small profiler installs as the first ScreenTune startup task. It writes one log per boot containing:
- Milestone timestamps — read from
/proc/uptime(seconds since power-on) as each key process or network event appears: main UI process, touch input, WiFi access point, phone association, CarPlay session, audio stream. - A steady-state resource snapshot — taken ~3 minutes after boot: process count, free memory, per-process memory, and load average.
The profiler itself is deliberately cheap (one process scan plus one sleep per loop, under ~1% CPU), so it doesn’t distort what it measures.
The two captures
Section titled “The two captures”| Capture | Build | Boots |
|---|---|---|
| Stock baseline | Profiler only, no other changes | 7 |
| ScreenTune | Full performance build | 6 |
Both ran on the same CMU and firmware, captured back-to-back. Each milestone below is the number of seconds from power-on to when that event appeared in the log.
Boot timing
Section titled “Boot timing”Typical times
Section titled “Typical times”These are the typical (middle-of-the-pack) times for each milestone:
| Milestone | Stock (typical) | ScreenTune (typical) | Sooner by |
|---|---|---|---|
| Interactive screen up | ~48 s | ~32 s | ~16 s |
| Touch ready | ~48 s | ~32 s | ~16 s |
| WiFi access point ready | ~55 s | ~39 s | ~16 s |
| Phone Wi-Fi associated | ~62 s | ~50 s | ~13 s |
| CarPlay session active | ~71 s | ~55 s | ~16 s |
| Audio stream running | ~71 s | ~57 s | ~14 s |
The two milestones that matter most to a driver are CarPlay connected (about 16 seconds sooner on a typical start, up to ~20 s on a good boot) and full responsiveness (about 16 seconds sooner). The earlier idea that the WiFi/CarPlay tail “barely changed” was based on an older tweak set; the current build improves that tail too.
Per-boot ranges
Section titled “Per-boot ranges”Because boot-to-boot variation is real, here is the full spread across every boot in each capture (fastest to slowest, in seconds from power-on):
| Milestone | Stock (7 boots) | ScreenTune (6 boots) |
|---|---|---|
| Interactive screen up | 46.8 – 57.1 | 31.4 – 32.5 |
| Touch ready | 47.0 – 57.4 | 31.5 – 33.7 |
| WiFi access point ready | 53.4 – 67.3 | 38.8 – 42.6 |
| hostapd (AP service) up | 54.6 – 69.2 | 39.6 – 43.5 |
| Phone Wi-Fi associated | 59.1 – 76.1 | 48.9 – 55.4 |
| CarPlay session active | 64.9 – 84.8 | 51.3 – 71.4 |
| Audio stream running | 65.8 – 99.0 | 55.4 – 72.2 |
The screen-ready and WiFi/hostapd milestones are the most consistent — ScreenTune clusters them tightly (the screen comes up in a ~1-second window every boot). CarPlay varies more, on both builds, because the last stretch before CarPlay is partly the phone’s own Wi-Fi and CarPlay handshake, which the head unit doesn’t control.
Resource load
Section titled “Resource load”Measured at steady state, ~3 minutes after boot. ScreenTune skips startup work for hardware your car doesn’t have and online services that have shut down, which frees memory and processor time:
- It runs about a dozen fewer background processes than the stock baseline.
- It leaves noticeably more RAM free for the menus and CarPlay to use.
That headroom is what keeps scrolling smooth and gives CarPlay rendering room to breathe, instead of competing with background tasks. The biggest memory users (the CarPlay runtime and the navigation and Bluetooth services) stay the same; ScreenTune removes the dead services sitting around them rather than shrinking those.
Limitations
Section titled “Limitations”Read these numbers as a directionally-strong measurement, not a spec sheet:
- Small sample. 6 ScreenTune boots vs 7 stock boots. Enough to see a clear, repeatable trend; not enough for tight error bars. Real-world numbers will vary boot to boot.
- One unit. All captures are from a single bench CMU on v74.00.324A. A different unit, firmware, or vehicle wiring will shift the absolute numbers.
- The phone-handshake tail varies. The last ~12–16 seconds before CarPlay is partly your phone’s own Wi-Fi/CarPlay handshake, which the head unit can’t speed up. One slower ScreenTune boot reached CarPlay at ~71 s (about the same as a typical stock boot), while the typical ScreenTune boot is ~55 s. A good ScreenTune boot reaches CarPlay near 51 s — about 20 s sooner than a typical stock start — which is why we cite the CarPlay win as a 16–20 s band rather than a single number.
- CarPlay reached on 6 of 6 ScreenTune boots and 6 of 7 stock boots (the 7th stock capture was cut short by the next restart, not a failure).
Reproduce it yourself
Section titled “Reproduce it yourself”The same profiler ships in every ScreenTune build. After driving, the next service USB collects each boot’s log automatically, so you can compare your own car’s before and after on the unit you actually own.