I've been refining the HOWTO.
Blur Busters Scanline Sync HOWTO
1. It works with any GPU. And any display including CRT.
2. You need a very powerful GPU
3. You need to try to get your 0.1% frametime no more than a refresh cycle. Upgrade GPU, decrease Hz, decrease detail, etc.
4. If properly configured, it looks like a lagless version of VSYNC ON.
5. If improperly configured, it will look like an ugly mess.
6. It can help make ULMB stutterless without the lag.
7. There's a way to get S-Sync working with Fast Sync and Enhanced Sync too
8. Enable the Scanline Sync hotkeys, it makes calibration easier (arrow keys to move the tearline UP/DOWN)
Scanline Sync can give you glassfloor frametimes in certain games .... A perfect 18-20ms lag glassfloor is always better than 16.7ms with lots of 33ms spikes.
Enable the Hotkeys to manually move the tearline up/down Add SyncHotkeys=1 to your config file to enable shortcuts. Hold CTRL+SHIFT while using UP/DOWN arrow to move the tearline up and down.
Calibration & Tuning Mantra: Always calibrate RTSS Scanline Sync with keyboard using VSYNC OFF first before turning VSYNC ON / Enhanced Sync / NVIDIA Fast Sync!
The tearline position is a wonderfully excellent visual calibration indicator.
Combining RTSS ScanLine Sync with your preferred sync mode:
VSYNC OFF: Calibrate tearline offscreen
Fast Sync: Calibrate tearline to stay permanently above bottom edge
Enhanced Sync: Calibrate tearline to stay permanently above bottom edge
Once you finish calibrating, switch to your preferred sync mode.
Tearline vibrates too much? (e.g. 1/4th screen height vibrations or worse)? Move the tearline onscreen and work hard to calm down your tearline first! Temporarily ignore the lag during this calibration stage, and focus on calming down the tearline first. Try increasing SyncFlush numbers by 1. Use SyncFlush 1. Also, lower refresh rates produce calmer tearlines. And lower CPU%, lower GPU% utilization will produce calmer tearlines too. Turning off certain features like AA will also produce calmer tearlines. If you are running very old games that always stay well below GPU 50%, try SyncFlush 2 as that produces very tranquil & calm tearlines. (Don't worry, the crazy increase in GPU% will be more than compensated by the complete lack of lag spikes; keep reading. That shiny glass floor lag beckons!). Remember, the calmer the tearline, the more likely it stays permanently near one location. Fiddle until you see your tearline calm down (vibrating consistently in a reasonably tight vertical space rather than all over the vertical dimension of the screen). The calmer the tearline, the more likely it stays permanently away from the bottom edge of screen. Thereby avoiding lag spikes if using another sync mode than VSYNC OFF. Tearlines that dips below bottom edge of screen exactly equals a latency spike if you were running FastSync instead of VSYNC OFF.
Framerates often below Hz: If your game cannot sustain framerate equal refresh rate, you WILL get lag spikes (with accompanying microstutter), no matter what. So lower your refresh rate and/or upgrade your GPU and/or adjust game detail and/or reduce AA.
Occasional framerate dips:
Occasional framerate dips: For using scanline sync with VSYNC OFF, you ideally prefer 99.9% framerate matching refresh rate. But for combining Scanline Sync with Fast Sync / Enhanced Sync, it is okay if there's occasional framerate dips -- such as disk access -- e.g. you're able to sustain full framerate matching refresh rate 90%+ to 95%+ of the time, so just aim for the 90th or 95th percentile of permanence. For emulators or older games, it's easy to aim at the 99th+ percentile though, but for newer games, just merely getting 90th percentile can sometimes be hard. A stutter will be a visual indicator of a lag spike, so if you're getting stutters during competitive-critical gameplay, then you definitely want to calibrate for framerate permanence above that, to improve aiming during critical heated moments. You might not be able to do anything about those disk access stutters, but at least you've calibrated for your critical moments.
Extra safety margin: For all of modes other than VSYNC OFF -- I recommend moving the tearline least 1/10th screen height above the bottommost visible tearline (where the tearline vibrates downwards to). Basically you should have a 1/10th area above bottom edge of screen that you've never seen the tearline vibrate downwards to. This gives you "padding". This adds 1/10th refresh cycle extra lag (~1.6ms at 60Hz) but will eliminate your lag spikes during Fast Sync, etc. If you're trying to synchronize at 120Hz or 144Hz, try 1/5th screen height of padding above bottom edge of screen.
What about SyncScanLine1 for twice framerate versus refresh rate?:
- If unfamiliar with this, keep SyncScanLine1 setting to 0. Worry only about one tearline (SyncScanLine0 or via GUI)
- Even if you do this, please do the easy stuff first before attempting this
If your game is ultra-low GPU (e.g. Quake Live or CS:GO) combined with motion blur reduction, this can reduce strobe lag a further (e.g. 240fps at 120Hz, or 200fps at 100Hz). First, calibrate using VSYNC OFF. You may use two tearlines with Enhanced Sync or Fast Sync -- but not with VSYNC ON (that will frame-throttle you badly). Calibrate the middle tearline to middle of screen (slightly above middle is ideal, to keep it equidistant with the bottommost tearline, but position of middle tearline matters less than the bottommost tearline) but focus on carefully calibrating the bottommost tearline to stay permanently above bottom edge of screen. Ideally, they should be signal-equidistant from each other (half Vertical Total apart, taking into account of VBI versus visible vertical resolution). But this is less critical than keeping the bottommost tearline permanently above bottom edge of screen, in order to avoid those lag spikes during Fast Sync and Enhanced Sync.