Why do LCD displays need blank intervals ?

[LastExceed]

I understand that these intervals were initially implemented to give CRT monitors time to realign the electron gun, but why do we still configure front and back porches for LCD displays ? I've tried using a custom resolution with all porches set to 1 and it seems to work just fine.

And second question, what exactly is sync width ? the blog post defines it as "duration of the sync pulse". if I understood correctly, the sync pulse is used to keep the pixel clock synchronized, which makes sense to me, but why does it have a duration ?

[ToastyX]

It's mostly a holdover from the CRT days, but digital monitors still need time to process the signal. Many LCD monitors can't handle very low blanking intervals. I find with most monitors, the total blanking matters more than the individual porch/sync parameters.

Blanking also has other uses. HDMI uses the blanking periods to transmit audio and other data. Video cards use the vertical blanking time to retrain the memory when changing clock speeds so it doesn't corrupt the screen contents. FreeSync uses the vertical blanking time to delay the next refresh until a frame is ready.

The sync pulses are mainly to mark the start of the next line/frame. I don't know why there's a duration, but it might be because analog signals weren't always reliable, so the duration was designed to be long enough so it can be detected with lower-quality signals.

[LastExceed]

very helpful, thanks!