LCD Monitor only getting to 60Hz when 75Hz available ??

lagagnon · 2010-01-03 15:32:18

My monitor is a Hansol H950 which is capable of 1280x1024 at 75Hz vertical refresh. The ratings are hsync 79.9 and vertrefresh 75 at 1280x1024. I put this info in xorg.conf as below:

Section "Monitor"
        Identifier   "Monitor0"
        VendorName   "Monitor Vendor"
        ModelName    "Monitor Model"
        HorizSync    79.9
        VertRefresh  75.0

However, "nvidia-settings" and "xrandr" report I am using only 60Hz resolution. When I try "xrandr -r 75" I get a response: "Rate 75.0 Hz not available for this size". Video chip is nVidia FX-5600 and I have the correct driver installed. Any ideas why I cannot get to 75Hz?

Dheart · 2010-01-03 15:50:15

nvidia-settings and xrandr are not always accurate.
Check your from your monitor, it should report the refresh rate (some option in the monitor menu).
Otherwise I think that with nvidia chip you can't add refresh rate via xrandr, rather you have to use some of the nvidia-settings...
Anyways try the following:
generate your mode with gtf:

gtf 1920 1080 30

Follow these instructions in my post.

Last edited by Dheart (2010-01-03 16:50:44)

lagagnon · 2010-01-03 16:48:07

DHeart: thank you for that info, I am trying it now. However, on tjhis command I am unsure what the device name is supposed to be:

xrandr --addmode DVI1 1280x1024_75.00"

I have tried "Monitor0" "Screen0" and other obvious device names from xorg.conf. None of these work. How d I get the actual monitor device name for xrandr operations?

Dheart · 2010-01-03 16:51:16

lol wrong link in my post, I edited and fixed it, check it out.
otherwise use xrandr to see the device you're using.

wantilles · 2010-01-04 00:07:48

A DVI connection only supports 60Hz.

You do not need anything more in a DVI connection anyway.

lagagnon · 2010-01-04 03:10:19

wantilles: thanks! Did not realize that, but was suspecting such when I checked the Monitor Menu itself and it said 60Hz. Thanks for the info! I don't need to mess around wasting my time then!

Gen2ly · 2010-01-04 05:09:08

Btw, 75Hz refresh rates don't provide any useful benefit. 75Hz means the the graphic board will draw the screen 75 times per second. Since the human eye is only capable of viewing around 60 fps (this is pretty consistent) then 75Hz refresh rates are pretty unnecessary.

ewaller · 2010-01-04 07:12:35

Also, LCD displays do not flicker as do CRT displays. The light output of a CRT pixel is brightest just after that pixel is output. For the next 1/60 th (or 1/75th) of a second, the light output from that pixel decays. Analog interlaced TVs only update pixels every 1/30th of a second (or 1/25th of a second for PAL). By interlacing, the flicker is reduced.

LCDs are slightly different. For all intents, an LCD pixel is a shutter which retains its setting for much longer than a refresh period (They don't decay / flicker). This is why you can photograph LCDs with arbitrary, non synchronous shutter speeds. The problem with LCDs traditionally been a long response time (time to change a pixel setting) Modern LCDs are getting pretty good with response times on the order of 10 to 20 mS.

The point of all this is that higher frame rates on LCDs really don't help. What is worse, is that LCD panels usually can only operate at one frequency/frame rate. If the controller does permit different frame rates than the native LCD speed, all that really happens is that the data are clocked in at one rate, undergo a frame rate conversion as the data are clocked out at the LCD's rate. This ultimately results in partial and or dropped frames.

Just my 2 cents from a guy who works with LCD interfaces at his day job.

Dheart · 2010-01-04 07:14:55

Strange... I've always been able to spot the difference between 60 and 75 Hz on LCD monitors... I guess it's just my bad eyes...

wantilles · 2010-01-04 15:29:40

Dheart wrote:

Strange... I've always been able to spot the difference between 60 and 75 Hz on LCD monitors... I guess it's just my bad eyes...

That's because you are using analog (VGA) connection, and not digital (DVI or HDMI).

R00KIE · 2010-01-04 18:21:51

It is rare but _some_ LCD monitors behave slightly different in terms of response time when you change the refresh rate, however the reason for wanting to use the highest refresh rate possible comes from the use of CRTs just like ewaller said.

The image in an LCD for all intents and purposes does not flicker so the recommended refresh rate should be used (typically I think it is 60Hz).

Arch Linux

#1 2010-01-03 15:32:18

LCD Monitor only getting to 60Hz when 75Hz available ??

#2 2010-01-03 15:50:15

Re: LCD Monitor only getting to 60Hz when 75Hz available ??

#3 2010-01-03 16:48:07

Re: LCD Monitor only getting to 60Hz when 75Hz available ??

#4 2010-01-03 16:51:16

Re: LCD Monitor only getting to 60Hz when 75Hz available ??

#5 2010-01-04 00:07:48

Re: LCD Monitor only getting to 60Hz when 75Hz available ??

#6 2010-01-04 03:10:19

Re: LCD Monitor only getting to 60Hz when 75Hz available ??

#7 2010-01-04 05:09:08

Re: LCD Monitor only getting to 60Hz when 75Hz available ??

#8 2010-01-04 07:12:35

Re: LCD Monitor only getting to 60Hz when 75Hz available ??

#9 2010-01-04 07:14:55

Re: LCD Monitor only getting to 60Hz when 75Hz available ??

#10 2010-01-04 15:29:40

Re: LCD Monitor only getting to 60Hz when 75Hz available ??

#11 2010-01-04 18:21:51

Re: LCD Monitor only getting to 60Hz when 75Hz available ??

Board footer