Problem with refresh rates

[Guest _Max_]

Hi,

 

I am having some problems with the refresh rate for my monitor and need some help!

 

I use an Intel 845G graphics card and a Dell P990 monitor, which defaults to 75 kHz under Windows for 1280x1024.

 

When I run Linux, however, it goes down to 60 kHz for any resolution, and I get headaches. The manual says it is capable of 120 kHz vertical and 96 horizontal, and that 1280x1024 at 85 kHz VESA is the recommended configuration - so I don't understand why it is doing this.

 

After reading this tutorial: http://www.mandrakeusers.org/viewtopic.php...ghlight=refresh , I decided to try to put my own modeline into my XF86Config-4 file.

 

First, I tried read-edid both under DOS, Linux and even on a different machine with the same monitor to see whether the monitor can tell me what a good configuration is. It turned out that I got what looks like rubbish to me in all three cases (only a 768x576 resolution with 61.1 kHz suggested) - that's probably the reason that I have this problem in the first place.

 

I then tried the modeline calculator suggested in the tutorial above to get a 1280x1024 resolution with 85 kHz (VESA), and this is what I got:

Modeline "1280x1024" 157.5 1280 1328 1488 1728 1024 1025 1028 1072 +hsync +vsync

 

I pasted this into the Monitor section of my XF86Config-4 file and remmed out the other modelines, but when I start X, I still have the same problem.

 

Somehow, I get the impression that I am missing something obvious.

 

Any suggestions?

 

Thanks....

 

(Oh, yeah, and I am using Mandrake 9 which comes with XFree86 4.2.1, I think).

[fuzzylizard]

Monitor refresh rates are a two part formula: one part is what your monitor is capable of and the second part is what your video card is capable of. My guess is that you are running into problems with the video card.

 

Once you are dealing with a resolution of 1280x1024 you will need more then onboard video to achieve a refresh rate higher then 75KHz. And the fact that you are getting garbage with anything higher definitely signals a limitation of the video card.

 

My suggestion would be to use a lower resolution, thus enabling a higher refresh rate. Or buy a real video card.

[Guest ndeb]

I use an Intel 845G graphics card and a Dell P990 monitor, which defaults to 75 kHz under Windows for 1280x1024.

U mean 75Hz, not kHz. Vertical refresh rates are in Hz.

 

fuzzylizard,

Its not a limitation of the video card and/or the monitor if the above claim is true. Its is a problem of the XFree86 intel driver (i810).

 

_Max_,

U should run xvidtune to check if u can get 75Hz+ at 1280x1024@32bpp (32bpp means 24bit color depth). Then u will get the exact settings (assuming u get what u want) for ur modeline.

 

If u don't get what u want, beware that the i845 video (and its older brother, the i830) has a painful history with linux/XFree86 as described in http://www.cse.unsw.edu.au/~chak/linux/c400.html and http://www.xfree86.org/~dawes/845driver.html .

Some pre-compiled drivers are available in http://www.jongans.com/gateway1450.html .

[Guest _Max_]

Hurrraah! It's working know!

 

Thanks, ndeb. After reading the links, I tried xvidtune, fiddled with the modeline some more and increased the videoram settings, and it's working now (still with the old i810 driver).

[Guest ndeb]

Good to hear that. How much Video RAM does the i845 have ? Also, whats the best resolution that u get on windoze: 1280x768x32bpp@75Hz ? Does the best on windoze match the best on linux ?

[Guest _Max_]

i845 can grab memory from the main system memory, so it's adjustable. The BIOS sets up to 8MB aside for video only, but it can the request more from the system, up to a total of 64MB. I guess that if you want to run something at a good resolution with high color depth and a good refresh rate, you need more than the standard setting.

 

The best resolution I have tried for Bill's OS was also 1280x1024, but for some reason it defaults to 75 Hz whatever the resolution (same for 1024x768) (both with 32bpp). And I haven't figured out how to change that under Windows. So for what I have tried, it looks better under Linux.

 

Allegedly, the monitor can also handle 1600x1200 at 75 Hz, but I haven't tried that.

[Guest ndeb]

i845 can grab memory from the main system memory, so it's adjustable. The BIOS sets up to 8MB aside for video only, but it can the request more from the system, up to a total of 64MB.

Actually, since i845 is integrated video, it uses the shared (or stolen) memory (from the system RAM). The 64MB is the AGP aperture size which is needed to support hardware acceleration (2d and 3d), which is optional. Now, 1280x1024x32bpp => 5MB, which is sustainable with 8MB of RAM.

In my experience, on a prosavage km133 integrated video with 8MB shared RAM, two X displays (1024x768x32bpp and 1024x768x16bpp) can be run simultaneously with 2d (xvideo) enabled (but no 3d).