Experiment with 2 monitor and a laptop

melw · 2011-09-12 12:15:25

I got 2 older monitors from a friend (Dell 1905fp) the other day. They are working as they should and so on. But is it possible to run these 2 on a laptop with only 1 VGA and 1 HDMI? The monitors do have 1 VGA and 1 DVI. I guess it's possible to get a USB to VGA device if it's necessery.

Since this is a laptop and i'm using it on other places then at home, is it possible to make the laptop to switch from using the laptops monitor to 2 monitors in some easy way? Using subtle atm, but planning to give dwm a try.

This is just an experiment, but it would be nice to make it work. If there is no way i'm probobly use the 2 monitors with an older desktop i got laying around somewhere...

gorky · 2011-09-12 19:44:14

melw wrote:

But is it possible to run these 2 on a laptop with only 1 VGA and 1 HDMI? The monitors do have 1 VGA and 1 DVI.

Should be possible, HDMI to DVI adapters usually work without problems (the connectors are electrically the same).

melw wrote:

I guess it's possible to get a USB to VGA device if it's necessery.

You'll probably have many troubles getting it to work under Linux (I've heard of only a few successful attempts).

melw wrote:

Since this is a laptop and i'm using it on other places then at home, is it possible to make the laptop to switch from using the laptops monitor to 2 monitors in some easy way?

Use xrandr, probably with some kind of graphical interface.

melw wrote:

This is just an experiment, but it would be nice to make it work. If there is no way i'm probobly use the 2 monitors with an older desktop i got laying around somewhere...

If it is an experiment I'll try to start from using a HDMI to DVI cable or adapter, because they are dirty cheap.

Last edited by gorky (2011-09-12 19:44:35)

Gusar · 2011-09-12 19:50:21

One thing you should know is that only two outputs can be active at the same time. So it's either internal display + one external display, or both external displays. Knowing that you shouldn't have any problems, just get what gorky mentions, a hdmi-dvi adapter.

melw · 2011-09-13 10:27:11

Thanks gorky and Gusar.

Will try with a HDMI to DVI cable, or some kind of adapter solution.
In VGA it shouldn't be any problem running 75MHz, but i read somewhere that i can only go for 60MHz with DVI. Can't really find anything about that when searching the internet and on Dell's product information (for the monitors) no difference between VGA and DVI is mentioned. Anyone knows anything about this or is it just bullshit?

gorky · 2011-09-13 11:38:46

For LCD use 60Hz exclusively, they don't flicker at all so no use for higer refresh rates.

Gusar · 2011-09-13 11:45:21

Yeah, DVI is usually 60Hz. But that's totally ok, because 60Hz with DVI means something different than 60Hz with VGA. You don't need more than that with DVI, whereas with VGA you certainly do (unless you enjoy flickering induced headaches )

gorky · 2011-09-13 11:50:00

Gusar wrote:

Yeah, DVI is usually 60Hz. But that's totally ok, because 60Hz with DVI means something different than 60Hz with VGA. You don't need more than that with DVI, whereas with VGA you certainly do (unless you enjoy flickering induced headaches )

60Hz means the same with DVI and VGA, the difference is that LCD don't flicker as CRT do.
So if you dont have a CRT monitor just use 60Hz and it will be ok.

melw · 2011-09-13 14:35:58

2 different answers, nice.
Btw, i'm gonna use 2 LCD monitors.

Seems like there are lots of argueing bout this (60 MHz or more with LCD monitors), most of them between gamers. Seems like the limitation is in the LCD technology, wich makes them run best on 60 MHz. But after googleing for 30-45 mins, it's hard to get some real fact, they mostly argue and it's hard to get any good facts from that

Well, seems like i'm not gaining anything from using 75 MHz, so all i need to do now is getting a DVI cable for my monitor (only got VGA atm) and i'll start playing around with 2 monitors tomorrow (i hope).

Thanks btw

gorky · 2011-09-13 15:02:00

melw wrote:

Seems like the limitation is in the LCD technology

It's not the limitation, it comes from completely different method of generating picture

In CRT you had a gun, which had to shoot electrons to the screen. It shot them line by line, and refresh rate was indicating how many times per second a line was 're-shot'.
In LCD, hovewer, you can light up individual pixel, and once lit it doesn't need to be 'refreshed' - it's still on.

The only 'limitation' is that on LCD with 60Hz refresh rate you can lit (or put out) a pixel no more than 60 times per second (it comes from liquid crystal transition time and steering), which gives you a maximum framerate of 60FPS.
But when confrontated with the fact that human eye has 'refresh rate' about 25FPS it still seems rather high...

Last edited by gorky (2011-09-13 15:06:00)

melw · 2011-09-14 04:11:00

Didn't know what to call it, so i called it limitation

Shouldn't the update depend on the LCD monitors responsetime? If the monitor can change a pixel in 5 ms, shouldn't the refreshrate end up at 200 per second?

Bah, was waaaay too long since my ass was at school, learning bout this stuff

gorky · 2011-09-14 11:53:59

melw wrote:

Shouldn't the update depend on the LCD monitors responsetime? If the monitor can change a pixel in 5 ms, shouldn't the refreshrate end up at 200 per second?

Theoretically it could depend on the time of pixel change, but it literally doesn't need to be as high, because 60 times per second is completely enough for LCD.

Also be aware that response time provided by the manufacturers is usually a lie, on average it takes two or three times more for the pixel to change.

Last edited by gorky (2011-09-14 11:54:59)

melw · 2011-09-14 22:03:02

Since i'm not gaming any more (job, a kid and a house takes all my time) i don't really care. Will be fun trying this experiment with the 2 monitors. Just got my new keyboard and mouse, so now it's time to become a nerd again

Arch Linux

#1 2011-09-12 12:15:25

Experiment with 2 monitor and a laptop

#2 2011-09-12 19:44:14

Re: Experiment with 2 monitor and a laptop

#3 2011-09-12 19:50:21

Re: Experiment with 2 monitor and a laptop

#4 2011-09-13 10:27:11

Re: Experiment with 2 monitor and a laptop

#5 2011-09-13 11:38:46

Re: Experiment with 2 monitor and a laptop

#6 2011-09-13 11:45:21

Re: Experiment with 2 monitor and a laptop

#7 2011-09-13 11:50:00

Re: Experiment with 2 monitor and a laptop

#8 2011-09-13 14:35:58

Re: Experiment with 2 monitor and a laptop

#9 2011-09-13 15:02:00

Re: Experiment with 2 monitor and a laptop

#10 2011-09-14 04:11:00

Re: Experiment with 2 monitor and a laptop

#11 2011-09-14 11:53:59

Re: Experiment with 2 monitor and a laptop

#12 2011-09-14 22:03:02

Re: Experiment with 2 monitor and a laptop

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