Refresh rates: why?

[XTF]

Why do LCD monitors still have a fixed refresh rate? There's no gun shooting at the screen with fixed horizontal and vertical frequencies.

If the videocard could just push a new frame (up to a certain limit) to the monitor when one was ready, certain things would work a lot better.

 

[dowant120hz]

its probably a few dollars cheaper
and there is no industry standard for it

 

[DoubleTap]

The most likely reason is that when LCDs came out, they had to work with computers that were designed to work with CRTs - so they had to work in a way that made them compatible. New LCD screens had to work with the old LCD screens, etc.

That's how most obsolete tech lives well past it's prime.

 

[XoR]

first LCD needs to be refreshed. If you would not refresh one picture would start to blur. So such system would need either monitor to have memory or just be still refreshed...

and it would be cheaper and easier to push current scheme to 200Hz than trying to change it...

another thing is that such change would be only really useful in games...

 

[XTF]

first LCD needs to be refreshed. If you would not refresh one picture would start to blur.

Why would it blur?

So such system would need either monitor to have memory or just be still refreshed...

Monitors already buffer, otherwise there'd be no input lag.

another thing is that such change would be only really useful in games...

What about 24 hz movies?

 

[tk-don]

LCD monitors have a fixed refresh rate, because the lcd matrix controller needs to switch on/off transistors based on a data stream it receives. (6-10 bits for each pixel, i.e. at least 6-10 clock cycles for each pixel).
They don't have any front or back porch, though... it can be completely avoided unlike CRTs.
You can keep increasing the required pixel clock, resulting in higher and stricter requirements regarding internal cable management. So an upper limit definitely exists for what is reasonable.
It's the lcd controller board that determines what the input refresh rate should be converted to. Most of these convert everything to 60 Hz. Maybe because they don't want people to observe "pixel walk", i.e. interference with the pixel clock and CCFL switching frequency.

 

[XoR]

ah, there is also necessity to change polarisation of voltage holding pixels to not destroy them and normally it's done with refresh cycle

Why would it blur?
voltage of one pixel leak to another. Matrix probably could be made to not exhibit this behavior but it would need much more transistors or other micro elements per pixel and that would make cost just ridiculously high... or it would need buffers but that would probably just add input lag as monitors makers are lazy...

Monitors already buffer, otherwise there'd be no input lag.
monitor don't really need buffers and cheap monitors don't have much input lag.
Buffers are needed for #2 generation RTC and some monitors have stupid processing pipeline like U2410 add 16.6ms input lag just to make place for PiP, even when it's not used...

What about 24 hz movies?
Most monitors can get around it by 72Hz mode and 120Hz monitors don't have issue as it's already dividable by 24

 

[XTF]

ah, there is also necessity to change polarisation of voltage holding pixels to not destroy them and normally it's done with refresh cycle

Why would it blur?
voltage of one pixel leak to another. Matrix probably could be made to not exhibit this behavior but it would need much more transistors or other micro elements per pixel and that would make cost just ridiculously high... or it would need buffers but that would probably just add input lag as monitors makers are lazy...

Is there an explanation somewhere of how LCDs work on such a low level?

Monitors already buffer, otherwise there'd be no input lag.
monitor don't really need buffers and cheap monitors don't have much input lag.

What's not much?

Buffers are needed for #2 generation RTC and some monitors have stupid processing pipeline like U2410 add 16.6ms input lag just to make place for PiP, even when it's not used...

That's silly indeed.

What about 24 hz movies?
Most monitors can get around it by 72Hz mode and 120Hz monitors don't have issue as it's already dividable by 24

A lot of monitors don't support 72 hz.