[SOLVED] Not the correct refresh rate on external monitor.
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I'm using Arch Linux and I just bought a ViewSonic P227f CRT monitor for photo editing, and while it works pretty well after just plugging it in, it seems that the refresh rates are a bit off.
The monitor is supposed to be able to do 1920x1440 @ 84hz, but I can only select 75hz in Gnome's monitor settings. The monitor is also supposed to be able to display 2048x1536@74hz, but I can't even select that resolution. There's just a garbled image at that resolution. I'm using it on a laptop with an Intel X3100 GPU. Is that why I can't use the highest resolution? Or is it because of incorrect modelines?
The monitor is identified in Gnome's monitor settings as 'ViewSonic Corporation 20"', which is also wrong since it's a 21" monitor.
I was able to locate the correct HorizSync and VertRefresh values in this post on the Ubuntu forums.
From what I gather the max pixel clock is 340mhz.
I tried making an xorg.conf that specified the hsync and vrefresh but it didn't make any difference. I also tried adding a new modeline to xrandr using a modeline calculator. But I couldn't really figure out how it worked. The calculator said that the "Dot clock" was over the max frequency and that I should use an interlacing mode.
Now, if there was a tool similar to Ubuntu's displayconf-gtk I imagine I could just set the correct model and be done with it. But since that is pretty much dead in favor of xrandr (i guess?) and doesn't exist for Arch anyway I think, is there a way to specify the correct model using xrandr?
Sorry if there's not enough info here. It's really the first time I had to use xrandr to actually do something so I don't know what info to include =/
Edit: I guess I can add this though: xorg.conf Xorg.0.log
Ignore the modeline in xorg.conf. It know it's probably not correct, but it didn't work without it either (still garbled image on that resolution).
Last edited by Synt4x_3rr0r; 06-17-2010 at 07:23 PM.
Thanks for your reply.
But I'm not sure what it is that you want me to find there.
I already have xorg set up and working, and I have tried adding the hsync and vrefresh to xorg.conf but without any luck, even though the log file seems to indicate that it is in fact using those values.
And the Intel page didn't seem to have any useful information for this problem either.
I guess I can live with 1920x1440@75hz though.
There's no flicker or anything like that. But it would be nice to be able to get the full 2048x1536@75hz that the monitor is supposed to be able to output.
Screen 0: minimum 320 x 200, current 3200 x 1440, maximum 8192 x 8192
VGA1 connected 1920x1440+1280+0 (normal left inverted right x axis y axis) 392mm x 294mm
1600x1200 85.0 + 75.0
1280x1024 85.0 75.0
1024x768 75.1 70.1 60.0
800x600 85.1 72.2 75.0 60.3
640x480 72.8 75.0 60.0
LVDS1 connected 1280x800+0+640 (normal left inverted right x axis y axis) 331mm x 207mm
TV1 disconnected (normal left inverted right x axis y axis)
Yes on lower resolutions 85hz works, just like it says in the xrandr output there.
But on the 2048x1536 and 1920x1440 line there it only states 75.0 in both cases. I know that the 2048x1536 resolution only goes up to 75hz like it says, but I only get a garbled image on that res. And I haven't been able to set 1920x1440 to 85hz either because gnome monitor settings only shows 75hz. I think I tried setting it through xrandr yesterday without any difference that I could tell.
Edit: On some of those resolutions the monitor is supposed to be able to handle over 100hz as well, and that doesn't seem to be the case if xrandr is to be believed.
Nothing happened when I did that. The screen didn't even blank or anything. And the xrandr output is still the same.
Edit: Could that mean that it is actually outputting 85hz and xrandr is reporting the wrong values?
It still doesn't explain why 2048x1536 doesn't work though.. But I guess that could be my laptop that isn't up to the task or something. I don't have another computer to try it with though =/
Last edited by Synt4x_3rr0r; 06-18-2010 at 12:39 PM.
I don't know what that mode would be named in a Modes line
"2048x1536" or "firstname.lastname@example.org" or "2048x1536@75" or what.
From what I gather the max pixel clock is 340mhz.
Based on what source of info? And whose max pixel clock? Max for the monitor? Max for Intel GM965/GL960 chip? Max for the DVI or VGA connection of the laptop?
I think 340MHz would be plenty for 2048 pixels plus retrace at 120.2KHz. But I'm not convinced every component from your video chip through to your monitor really can handle 340MHz. Maybe 2048 pixels plus retrace at 120.2KHz is too fast for some component.
How important is 75Hz to you (vs. 2048x1536)?
I would construct a modeline for 2048x1536 at a lower refresh rate and see if it works well.
So now it starts up at 1920x1440@75Hz, and I get an option of 2048x1536@60 in the gnome settings. But when I select that, the screen goes black and doesn't come back on until the countdown has ended. Edit: Oh and the regular 2048x1536@75Hz is still garbled.
Edit again: Sorry I'm a little tired...
I got the info about the pixel clock at ViewSonic's website, though for a smaller monitor, but that seems to be the only difference. That's also where I got the 79Hz from. It seems viewsonic has removed all info about my monitor from their website for some reason. The other monitor's page is located here.
Last edited by Synt4x_3rr0r; 06-18-2010 at 02:49 PM.
Yep, that modeline did it. So the monitor is too good for my laptop i suppose.
I think I'll stick to 1920x1440 for now because a lot of sharpness is lost at 60hz, but in some cases it can be good to have.
Thanks for your help!
Do you think it's possible to get 1920x1440@85Hz or is it the same there? The modeline generator gives me a Dot Frequency of 499.03 so I guess not :P
Edit: I figured it might work in interlaced mode. so i'm gonna try that now..
Last edited by Synt4x_3rr0r; 06-18-2010 at 03:38 PM.
Say I want a 65Hz refresh version of that. I put 65 into a calculator, then multiply that by 2.832 and multiply the result by 1.603. I got those two numbers (that I multiplied by) by inserting a decimal point in the two numbers in the positions of the original line I indicated in color. The result in my calculator is 295.08. I replace the green number in the original line by 295.08 and I put @65 into the quoted name of the mode, resulting in: