twinview, dual 19" ws lcds

musasabi · Posted: Sat Apr 14, 2007 7:37 pm Post subject: twinview, dual 19" ws lcds

just when i thought i had gentoo figured out, i had to go and try dual head. =)

heres my current issue - im running a geforce 7800gs with two 19" widescreen lcds (ViewSonic Q19wb-2). yay. id like to be running them both at 1440x900, 60hz, and have X be able to distinguish between the two of them (ie, maximize to only one screen, run ut2k4/nwn/doom3/etc on one screen and have the other blank or otherwise untouched, etc).

i read up as best i could and had a go at this last night, but ive been halted. whats going on right now is X is running on screen at what i think is 2880x1024, because i can scroll the virtual desktop up and down, but it fits perfectly laterally.

X handles my singled headed layout just fine. it runs 1440x900@52, though, which seems odd, considering windows uses 60hz by default. maybe im running the wrong horiz/vert refresh rates? i'll have to investigate.

i added xinerama to my global useflags and did an "emerge -pv --newuse world", but X, gnome, and all other window managers were absent from that list. firefox and a few apps were the only thing there. i recompiled them anyway, but nothing changed.

so from here im left with four basic questions: how do i fix my resolution? how do i set the proper refresh rate? what is RandR (when i go to change resolutions, i also get an error message from X, saying the XRandR extension isnt supported)? and, after all that is taken care of, how can i get X to treat these two screens as separated, so windows only maximize to one screen at a time?

thank you all. =)

EDIT: well, i changed the vertical and horizontal refresh rates, and now i can run my monitor at 50 or 55hz. apparently newegg had the wrong numbers up for this monitor. still not 60, but text doesnt flicker now, so im happy.

here is xorg.conf

krinn · Watchman Joined: 02 May 2003 Posts: 7470

you can find a complete documentation in /usr/share/doc/nvidia-(driversversion)

also a good sample XF86Config file

alternative you could simply try the nvidia tool, that seems to work
emerge nvidia-settings

BitJam · Posted: Sat Apr 14, 2007 10:58 pm Post subject: Re: twinview, dual 19" ws lcds

The Unknown · Posted: Sat Apr 14, 2007 11:07 pm Post subject:

I don't know about the XRandR, but I noticed a few things in your xorg.conf
you have 2 "Screen 2" you should only need one at least for twinview I use 2 lcd`s that are the same and I only list one Screen "Screen 1" thats it.

you also have 2 "Dual Head" ServerLayouts(you only need 1) your server layout for Dual Head is set for something like xinerama,for twinview you only need to set it up for 1 screen.

So your screen should only have one device and one monitor,take a look at the README from nvidia on how to set up metamodes for your individual monitors
twinview takes care of all the rest,respecting monitor borders.

Each DE will treat it slightly differently I found xfce does a great job. here's mine

hvengel · Guru Joined: 19 Sep 2004 Posts: 515

I ran twinview for a long time and stopped using it a few months ago. I did this for a number of reasons.

1. Since I use my system to do color critical work I need to be able to individually calibrate the monitors. This can NOT be done if you are running twinview but it can be done if you are using xinerama.

2. I only notice a very slight performance hit (perhaps 5% at most) in 3D games when using xinerama vs. twinview.

In other words the very small performance increase from twinview can at a very high cost in lost display calibration functionality. Also the nvidia drivers do not work with randr version > 1.1 for what that is worth.