Radeon 8500, 1024x768@100hz

Danodare · 03-05-2004, 11:17 AM

Hello, I have a radeon 8500 and a hitachi 19" monitor. Under windows 98se with ati driver, it runs in 1024x768 / 24 bits. The horizontal refresh rate in that mode is 82 khz, the vertical refresh rate is 100 hz.

Under linux (slackware 9.1), it won't go above 69 khz / 85 hz for the same mode (1024x768 / 24 bits).

The default "radeon" driver puts it at 69 khz / 85 hz.

The "fglrx" driver I downloaded from ati puts it at the exact same refresh rates.

I wonder why !

The first thing I did was to dig out my monitor manual, it says
31.5-93 khz for horizontal
50-160 hz for vertical
I entered those values in both xf86config (default radeon driver) and fglrxconfig (fglrx driver).

Things I may have done wrong:

1) Does the "fglrx" driver need a kernel recompile ? I use the bare.acpi kernel from the installation cd (kernel 2.4.24).

2) For high refresh rates, is there some kind of agp trick needed ? While kde is running, if I do a "lsmod", it says the module "agpgart" is unused.

3) During fglrxconfig, many many questions left me dumbfounded, so I just hit enter to get the default. Maybe there is one special answer to get high refresh rates ?

Thanks in advance,
-Danodare

aaa · 03-05-2004, 12:17 PM

The refresh rate is determined by 'Modeline' s in the /etc/X11/XF86Config . If you don't see any lines starting with the word 'Modeline' in your /etc/X11/XF86Config file, it means that X is using the default ones which are not good enough for you. Use this to generate a suitable modeline. Insert it into your XF86Config file in the 'Monitor' section. Example:

Code:

Section "Monitor"
Identifier "monitor1"
VendorName "Generic"
ModelName "Flat Panel 1400x1050"
HorizSync 31.5-90
VertRefresh 59-75

# Sony Vaio C1(X,XS,VE,VN)?
# 1024x480 @ 85.6 Hz, 48 kHz hsync
ModeLine "1024x480" 65.00 1024 1032 1176 1344 480 488 494 
563 -hsync -vsync

# TV fullscreen mode or DVD fullscreen output.
# 768x576 @ 79 Hz, 50 kHz hsync
ModeLine "768x576" 50.00 768 832 846 1000 576 590 595 630

# 768x576 @ 100 Hz, 61.6 kHz hsync
ModeLine "768x576" 63.07 768 800 960 1024 576 578 590 616

Danodare · 03-05-2004, 12:47 PM

First, thanks for answering

Second, the monitor reacted very badly to the Modeline. I quickly "Ctrl-Alt-Backspace" to kill X but it was definitely not working.

In my monitor's manual, they give horizontal sync width "0.8 - 3.0" microseconds as well as vertical sync width "less than 100" microseconds.

I am tempted to use these values in the page you linked, but is there any risk to kill my monitor if I try too many times ?

Thanks in advance,
-Danodare

aaa · 03-05-2004, 12:59 PM

Not sure about if you try too many times, but if it looks very funny, stop quickly. Modern monitors should stop themselves, but you never know. There is a howto at www.tldp.org on X modelines, if you want to know how to tweak the modelines yourself.

Danodare · 03-05-2004, 04:25 PM

I seem to be getting a better understanding of how this all works. Basically the Modeline command with its cryptic numbers is a composite of several elements. The following are equivalent:

# ModeLine "1024x768i" 45 1024 1048 1208 1264 768 776 784 817 Interlace

# Mode "1024x768i"
# DotClock 45
# HTimings 1024 1048 1208 1264
# VTimings 768 776 784 817
# Flags "Interlace"
# EndMode

DotClock is just obtained by simple mathematics. The real problem is to get the magic values for HTimings and VTimings.

Silly question, but I still have windows in dual boot for games, is there anyway for me to get the magic values from a windows program ?

Otherwise, I don't really see how to get them without torturing the monitor and making it confess.

Thanks,
-Danodare

aaa · 03-05-2004, 04:35 PM

Windows gets them automatically form the monitor. X is supposed to do that too, but apparently it didn't work too well. I'm guessing that Windows might store them in the Registry or something, but I don't think you can find them in something like the Display Applet.

I think you can obtain the timings via math (probably not so simple). The modeline generator does this. See the tldp guide, it explains everything in depth.

Danodare · 03-05-2004, 04:50 PM

I found an interesting page for "hitachi cm-751" owners by googling with new words:

http://xfree86.desiato.de/xfree86/pi...il/007131.html

Here are the three modelines I tried
# Modeline "1024x768" 126.64 1024 1056 1536 1568 768 781 794 807
# Modeline "1024x768" 115.85 1024 1056 1400 1432 768 783 792 807 -HSync -VSync
# Modeline "1024x768" 115.5 1024 1056 1248 1440 768 771 781 802 -HSync -VSync

First one got me thinking my monitor had exploded when I started X

Second one is really dark and screwy.
Third one is still bad, top of the screen is not working, but it's the best of the the three.

I will stop for today. Tomorrow I will try looking into the windows registry to see if I can find the monitor settings. Otherwise I will try xvidtune starting with the values in the third modeline, hopefully I will eventually get the true "magic" values to make it work.

I searched "www.tldp.org" for "modeline", and I get 19 answers... which one are you talking about ?

Thanks,
-Danodare