什麼是G-SYNC

關於G-SYNC，我們首先要知道到底什麼是“刷新率”。刷新率就是屏幕每秒鐘會展示的畫面。每秒展示60張畫面就是60Hz刷新率，每秒144張畫面就是144Hz刷新率.

刷新率究竟有什麼用呢？根據The Effects of Screen Refresh Rate on Editing OperationsUsing a Computer Mouse Pointing Device中實驗得出的數據，根據在不同刷新率下捕獲目標的時間，得出結論：捕獲目標時間隨着刷新率的提高而降低.

There was a significant effectof refresh rate in the time to capture the target, F(2, 36) = 5.56, p =0.008, with a pattern of means very similar to that found in Experiment 1(50 Hz: M = 2153 msec; 75 Hz: M = 1777 msec; 100 Hz: M = 1946 msec).

In contrast to the apparent de-couplingof eye and cursor during the initial phases of the movement, inspection ofreal-time plots of eye and cursor trajectories and the data reported hereconfirm the obvious conclusion that to perform the final phase of thetask, subjects directly inspect the cursor. At this point, performance isquite markedly worse at the relatively low refresh rate of 50 Hz. Insummary, rapid movements of the eyes across a pulsating surface appear tolead to a global degradation in performance, which increases at higherrefresh rates and is unrelated to perceived flicker.

更高的刷新率意味着你將擁有跟多的反應時間，這對於FPS類遊戲具有極大地優勢作用.

但是，明明有了更高的刷新率，爲什麼有時還是感覺畫面會發生卡頓. 我們來看看NVIDIA給出了什麼解釋：不幸的是，顯示設備的刷新率通常與渲染速率無關。例如，目前視頻被設計爲以24 Hz、60 Hz等固定速率播放. 也就是說，無論渲染速率是什麼，視頻都是以固定的速率顯示的，這是可變的。這導致引入了限制的方案，試圖補償不同的呈現和顯示刷新率之間的任何差異.

Unfortunately, the refresh rate of adisplay device has generally been independent of the rendering rate. Forexample, currently video is designed to playback at fixed rates of 24 Hz, 60Hz, etc. That is, video is displayed at a fixed rate no matter the renderingrate, which is variable. This has resulted in limited schemes being introducedthat attempt to compensate for any discrepancies between the differingrendering and display refresh rates.

也就是說，當顯卡（GPU）渲染幀率大於顯示器刷新率時，由於顯卡向顯示器短時間內傳輸了過多的畫面，顯示器無法快速完成畫面銜接處理，導致了畫面出現撕裂感. 即畫面會以一條甚至更多條分界線爲界，上下顯示的爲顯卡不同時刻輸出的畫面.

而NVIDIA G-SYNC有效解決了這個問題. 這項技術是由顯卡來主導顯示器，當顯卡繪製完成當前幀後會立即通知顯示來輸出畫面，這樣丟幀、撕裂、延遲都得到了解決.

由此以來解決了傳統垂直同步技術由顯示器主導顯卡，產生畫面延遲的問題. 爲PC用戶帶來了更流暢的體驗的同時減少了延遲輸入帶來的弊端.

文獻參考

[1] KENNEDY A,BACCINO T. The Effects of Screen Refresh Rate on Editing Operations Using aComputer Mouse Pointing Device[J/OL]. The Quarterly Journal of ExperimentalPsychology Section A, 1995: 55-71. http://dx.doi.org/10.1080/14640749508401375.DOI:10.1080/14640749508401375.

[2] NVIDIA CORP.VARIABLEREFRESH RATE VIDEO CAPTURE AND PLAYBACK: US2018061364[P]. 2018.03.01