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Taigo
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Location: the Netherlands
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 Posted: Sun Jun 23, 2024 3:18 pm Post subject: CRT monitor low resolution |
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| I bought an old cool CRT monitor from the flea market and it still works really well, but when i use it on Linux it does not seem to allow any resolution higher then 640x480 and refresh rate higher then 60hz. When i tried getting it connected using microsoft windows it seemed to work fine with a resolution of 1280x960 and 85hz, i could even force it higher up to 90hz. So i was wondering if i miss anything or if it's something that is not supported at all. I'm using a modern AMD graphics card with it's linux drivers of course. |
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RumpletonBongworth
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Joined: 17 Jun 2024
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| Posted: Sun Jun 23, 2024 4:28 pm Post subject: Re: CRT monitor low resolution |
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| Taigo wrote: | | I bought an old cool CRT monitor from the flea market and it still works really well, but when i use it on Linux it does not seem to allow any resolution higher then 640x480 and refresh rate higher then 60hz. When i tried getting it connected using microsoft windows it seemed to work fine with a resolution of 1280x960 and 85hz, i could even force it higher up to 90hz. So i was wondering if i miss anything or if it's something that is not supported at all. I'm using a modern AMD graphics card with it's linux drivers of course. |
It is common for CRT monitors to be able to to convey information regarding their supported resolutions as EDID data through VESA DDC. Here are some potential explanations for what is happening.
- your VGA cable is sub-standard and doesn't have the three pins used for DDC wired
- the EDID data cannot be read for some reason
- the data can be read but is being disregarded
- the unstated means by which you are trying to select a better resolution is oblivious to the EDID data
- there is a bug in a relevant component - possibly owing to the lack of testing on CRTs nowadays
Further, it is possible that the resolutions and refresh rates that are exposed by Windows might not be based on EDID data but, instead, on standards such as VESA CVT or VESA GTF.
Without any concrete information concerning your setup and operating environment - including whether you use X.Org or a Wayland compositor and whether you use any particular desktop environment - it's difficult to issue any specific recommendations. In the worst case, you might have to use X.Org and go back to the old method of manually defining modelines. If you are using X.Org, have you tried using the xrandr utility to evaluate the available resolutions? |
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NeddySeagoon
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| Posted: Sun Jun 23, 2024 5:49 pm Post subject: |
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Taigo,
All of what RumpletonBongworth said plus the display may be too old to even provide EDID at all.
Please use wgetpaste to share your Xorg.0.log. That will show what was detected, if anything.
640x480@60 Hz is the lowest common denominator, so is always safe on VGA.
It works in windows because Windows provides a look up table. That implies that Windows can detect at the the display model from the EDID data.
If all else fails, we can write modelines for the modes you want to use.
WARNING: CRT displays can be destroyed by attempting to operate them at at modes they are not designed to support.
This is because the EHT voltage is derived from the line scan rate. Higher line rates produce higher voltages.
Later models either blank the screen or display a Mode Out of Range warning.
What is the make and model of the display?
From the label on the back, not whatever Windows detects. That may not be right.
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NeddySeagoon
Computer users fall into two groups:-
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Taigo
Tux's lil' helper
Joined: 09 Nov 2022
Posts: 105
Location: the Netherlands
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| Posted: Sun Jun 23, 2024 6:26 pm Post subject: Re: CRT monitor low resolution |
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| RumpletonBongworth wrote: | | Taigo wrote: | | I bought an old cool CRT monitor from the flea market and it still works really well, but when i use it on Linux it does not seem to allow any resolution higher then 640x480 and refresh rate higher then 60hz. When i tried getting it connected using microsoft windows it seemed to work fine with a resolution of 1280x960 and 85hz, i could even force it higher up to 90hz. So i was wondering if i miss anything or if it's something that is not supported at all. I'm using a modern AMD graphics card with it's linux drivers of course. |
It is common for CRT monitors to be able to to convey information regarding their supported resolutions as EDID data through VESA DDC. Here are some potential explanations for what is happening.
- your VGA cable is sub-standard and doesn't have the three pins used for DDC wired
- the EDID data cannot be read for some reason
- the data can be read but is being disregarded
- the unstated means by which you are trying to select a better resolution is oblivious to the EDID data
- there is a bug in a relevant component - possibly owing to the lack of testing on CRTs nowadays
Further, it is possible that the resolutions and refresh rates that are exposed by Windows might not be based on EDID data but, instead, on standards such as VESA CVT or VESA GTF.
Without any concrete information concerning your setup and operating environment - including whether you use X.Org or a Wayland compositor and whether you use any particular desktop environment - it's difficult to issue any specific recommendations. In the worst case, you might have to use X.Org and go back to the old method of manually defining modelines. If you are using X.Org, have you tried using the xrandr utility to evaluate the available resolutions? |
It seems i have forgotten to mention that I am also using an adapter that converts VGA to DP input since my GPU does not have VGA ports and i don't have a GPU with my CPU so i also can't use the port on the motherboard.
The model as far as i can tell is that the brand is Phillips and on the top left it says 107b. I assume that Linux does not get this EDID data but i can't tell for sure. If it doesn't is there any way to force a certain resolution?
| NeddySeagoon wrote: | | Please use wgetpaste to share your Xorg.0.log. That will show what was detected, if anything. |
Here is the output of the command.
http://0x0.st/XAJA.0.log
| NeddySeagoon wrote: | WARNING: CRT displays can be destroyed by attempting to operate them at at modes they are not designed to support. This is because the EHT voltage is derived from the line scan rate. Higher line rates produce higher voltages.
Later models either blank the screen or display a Mode Out of Range warning. |
Mine did show a out of range warning when i tried putting the refresh rate too high |
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Taigo
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Joined: 09 Nov 2022
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| Posted: Mon Jun 24, 2024 12:32 am Post subject: Re: CRT monitor low resolution |
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| Taigo wrote: | | I bought an old cool CRT monitor from the flea market and it still works really well, but when i use it on Linux it does not seem to allow any resolution higher then 640x480 and refresh rate higher then 60hz. When i tried getting it connected using microsoft windows it seemed to work fine with a resolution of 1280x960 and 85hz, i could even force it higher up to 90hz. So i was wondering if i miss anything or if it's something that is not supported at all. I'm using a modern AMD graphics card with it's linux drivers of course. |
I've done some experimenting and I think it somehow does not obtain the EDID data when on linux. On windows it seemed to add resolutions supported by the screen as well as the refresh rate for the resolution that are specified in the manual I found online. when running xrandr --properties it shows an EDID for my LCD monitor but nothing for my CRT monitor. |
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RumpletonBongworth
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| Posted: Mon Jun 24, 2024 12:35 pm Post subject: |
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| Yes, that does seem to be the problem. Your log shows EDID data being obtained for what appears to be an Iiyama E2473HDS or B2473HDS monitor attached to the HDMI port but nothing else. |
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Taigo
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Joined: 09 Nov 2022
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Location: the Netherlands
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| Posted: Mon Jun 24, 2024 2:45 pm Post subject: |
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| RumpletonBongworth wrote: | | Yes, that does seem to be the problem. Your log shows EDID data being obtained for what appears to be an Iiyama E2473HDS or B2473HDS monitor attached to the HDMI port but nothing else. |
Yeah that is my "old" monitor that is also connected to the pc at the same time. Does this mean i need to manually write these lines for Xorg however you do that? |
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RumpletonBongworth
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| Posted: Mon Jun 24, 2024 3:04 pm Post subject: |
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| Taigo wrote: | | Does this mean i need to manually write these lines for Xorg however you do that? |
Perhaps there is some way to get EDID working for you but I am uncertain as to how. I'd probably resort to defining modelines if I were in your position. |
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Fitzcarraldo
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| Posted: Mon Jun 24, 2024 3:51 pm Post subject: |
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Taigo,
You wrote that your CRT monitor model is a Philips 107B. Post #21 in the following thread has sections in an xorg.conf for that model of monitor:
https://forum.ubuntu-fr.org/viewtopic.php?id=15442
Notice the Monitor and Screen sections in that xorg.conf refer to the Philips 107B:
| Code: | [...]
Section "Monitor"
Identifier "VNC Monitor"
Vendorname "Philips"
Modelname "Philips 107B(17inch/CM6800)"
Horizsync 30.0-69.0
Vertrefresh 50.0-130.0
modeline "800x600@75" 49.5 800 816 896 1056 600 601 604 625 +hsync +vsync
modeline "1024x768@75" 78.8 1024 1040 1136 1312 768 769 772 800 +hsync +vsync
modeline "1280x1024@60" 108.0 1280 1328 1440 1688 1024 1025 1028 1066 +hsync +vsync
Gamma 1.0
EndSection
Section "Screen"
Identifier "Default Screen"
Monitor "Configured Monitor"
Device "Configured Video Device"
Monitor "VNC Monitor"
Defaultdepth 24
SubSection "Display"
Depth 24
Virtual 1024 768
Modes "1024x768@75" "800x600@75" "1280x1024@60"
EndSubSection
EndSection
[...] |
I do not have that monitor model so I don't have any way of testing that, therefore YMMV.
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Taigo
Tux's lil' helper
Joined: 09 Nov 2022
Posts: 105
Location: the Netherlands
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| Posted: Mon Jun 24, 2024 4:41 pm Post subject: |
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| Fitzcarraldo wrote: | Taigo,
You wrote that your CRT monitor model is a Philips 107B. Post #21 in the following thread has sections in an xorg.conf for that model of monitor:
https://forum.ubuntu-fr.org/viewtopic.php?id=15442
Notice the Monitor and Screen sections in that xorg.conf refer to the Philips 107B:
| Code: | [...]
Section "Monitor"
Identifier "VNC Monitor"
Vendorname "Philips"
Modelname "Philips 107B(17inch/CM6800)"
Horizsync 30.0-69.0
Vertrefresh 50.0-130.0
modeline "800x600@75" 49.5 800 816 896 1056 600 601 604 625 +hsync +vsync
modeline "1024x768@75" 78.8 1024 1040 1136 1312 768 769 772 800 +hsync +vsync
modeline "1280x1024@60" 108.0 1280 1328 1440 1688 1024 1025 1028 1066 +hsync +vsync
Gamma 1.0
EndSection
Section "Screen"
Identifier "Default Screen"
Monitor "Configured Monitor"
Device "Configured Video Device"
Monitor "VNC Monitor"
Defaultdepth 24
SubSection "Display"
Depth 24
Virtual 1024 768
Modes "1024x768@75" "800x600@75" "1280x1024@60"
EndSubSection
EndSection
[...] |
I do not have that monitor model so I don't have any way of testing that, therefore YMMV. |
i copied the code into /etx/X11/xorg.conf but nothing changed. I never xonfigured anything about xorg by hand so there is a chance i might have been missing something simple. |
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RumpletonBongworth
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Joined: 17 Jun 2024
Posts: 77
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| Posted: Mon Jun 24, 2024 4:54 pm Post subject: |
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You may also need to associate the monitor identifier with the GPU port in question. I don't know which of DisplayPort-0, DisplayPort-1 and DisplayPort-2 it is in your case but you could try something like this:
| Code: | Section "Device"
Driver "amdgpu"
Option "Monitor-DisplayPort-0" "VNC Monitor"
EndSection
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Incidentally, it's a little misleading to have the identifier be named "VNC Monitor". Still, as long as it matches your Monitor section, it shouldn't matter. |
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Taigo
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Joined: 09 Nov 2022
Posts: 105
Location: the Netherlands
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| Posted: Mon Jun 24, 2024 5:12 pm Post subject: |
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| RumpletonBongworth wrote: | You may also need to associate the monitor identifier with the GPU port in question. I don't know which of DisplayPort-0, DisplayPort-1 and DisplayPort-2 it is in your case but you could try something like this:
| Code: | Section "Device"
Driver "amdgpu"
Option "Monitor-DisplayPort-0" "VNC Monitor"
EndSection
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Incidentally, it's a little misleading to have the identifier be named "VNC Monitor". Still, as long as it matches your Monitor section, it shouldn't matter. |
Replacing identifier with DisplayPort-1 fixed it and it applies now! But my favourite 1280x960@90 or 1280x960@85 is unfortunatly missing. I tried adding it manually with help of this tool https://arachnoid.com/modelines/index.html
but no luck with that... |
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RumpletonBongworth
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Joined: 17 Jun 2024
Posts: 77
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| Posted: Mon Jun 24, 2024 5:40 pm Post subject: |
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| I'm a little out of practice when it comes to modelines but if you share the config you last tried, perhaps someone will help you to figure it out. I don't suppose your config is very long so an inline [code][/code] block should be fine (pastebin entries expire, after all). |
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Taigo
Tux's lil' helper
Joined: 09 Nov 2022
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Location: the Netherlands
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| Posted: Mon Jun 24, 2024 5:47 pm Post subject: |
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My file currently looks like this
| Code: |
Section "Monitor"
Identifier "DisplayPort-1"
Vendorname "Philips"
Modelname "Philips 107B(17inch/CM6800)"
Horizsync 30.0-69.0
Vertrefresh 50.0-130.0
modeline "800x600@75" 49.5 800 816 896 1056 600 601 604 625 +hsync +vsync
modeline "1024x768@75" 78.8 1024 1040 1136 1312 768 769 772 800 +hsync +vsync
modeline "1280x960@90" 158.69 1280 1376 1512 1744 960 961 964 1011 -hsync +vsync
modeline "1280x960@85" 149.43 1280 1376 1512 1744 960 961 964 1008 -hsync +vsync
modeline "1280x1024@60" 108.0 1280 1328 1440 1688 1024 1025 1028 1066 +hsync +vsync
Gamma 1.0
EndSection
Section "Screen"
Identifier "Default Screen"
Monitor "Configured Monitor"
Device "Configured Video Device"
Monitor "VNC Monitor"
Defaultdepth 24
SubSection "Display"
Depth 24
Virtual 1024 768
Modes "1024x768@75" "1280x960@90" "800x600@75" "1280x1024@60" "1280x960@85" "1280x960@85"
EndSubSection
EndSection
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I just tried this but nothing i specified shows up anywhere at all. I'm not sure why it is wrong and being disregarded but the other modes do show up. |
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RumpletonBongworth
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Joined: 17 Jun 2024
Posts: 77
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| Posted: Mon Jun 24, 2024 5:52 pm Post subject: |
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I used the website that you mentioned to generate a modeline for 1280x960@85 and this is what I got.
| Code: |
# 1280x960 @ 85.00 Hz (GTF) hsync: 85.68 kHz; pclk: 149.43 MHz
Modeline "1280x960_85.00" 149.43 1280 1376 1512 1744 960 961 964 1008 -HSync +Vsync
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Note that the the hsync rate of 85.68 kHz is outside of the range of 30.0-69.0 that you defined. I would expect that this is the reason that the mode is not currently being exposed. |
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RumpletonBongworth
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| Posted: Mon Jun 24, 2024 6:01 pm Post subject: |
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Further, I just looked at the official technical specifications for the Philips 107B. The supported ranges are as follows.
Horizontal: 30 - 86kHz
Vertical: 50 - 160Hz
So, whoever wrote the sample config that you are using was simply guessing or, more likely, copying and pasting random values from elsewhere. |
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Taigo
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Joined: 09 Nov 2022
Posts: 105
Location: the Netherlands
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| Posted: Mon Jun 24, 2024 6:04 pm Post subject: |
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| RumpletonBongworth wrote: | Further, I just looked at the official technical specifications for the Philips 107B. The supported ranges are as follows.
Horizontal: 30 - 86kHz
Vertical: 50 - 160Hz
So, whoever wrote the sample config that you are using was simply guessing or, more likely, copying and pasting random values from elsewhere. |
Yes i just found this out. It seems to work now so thank you very much!
Altough when looking at the manual it says 92 is the maximum vertical refresh rate, did i perhaps miss something? |
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RumpletonBongworth
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Taigo
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| Posted: Mon Jun 24, 2024 6:18 pm Post subject: |
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Oh it seems you're right. But the 160hz doesn't seem usable or specified anywhere.
Also it seems when i was on windows i was using an out of range horizontal synz of 90khz and the monitor did not give me any warning of this. Is it still safe to use and go outside the bounds a little or should i absolutely stay inside that range in the manual. |
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Taigo
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Joined: 09 Nov 2022
Posts: 105
Location: the Netherlands
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| Posted: Mon Jun 24, 2024 6:22 pm Post subject: |
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In case someone sees this 25 years later with the exact same problem this is my current xorg.conf
| Code: |
Section "Monitor"
Identifier "DisplayPort-1"
Vendorname "Philips"
Modelname "Philips 107B(17inch/CM6800)"
Horizsync 30.0-86.0
Vertrefresh 50.0-160.0
modeline "800x600@75" 49.5 800 816 896 1056 600 601 604 625 +hsync +vsync
modeline "1024x768@75" 78.8 1024 1040 1136 1312 768 769 772 800 +hsync +vsync
Modeline "1280x960_85.00" 149.43 1280 1376 1512 1744 960 961 964 1008 -HSync +Vsync
modeline "1280x1024@60" 108.0 1280 1328 1440 1688 1024 1025 1028 1066 +hsync +vsync
Gamma 1.0
EndSection
Section "Screen"
Identifier "DisplayPort-1"
Monitor "Configured Monitor"
Device "Configured Video Device"
Monitor "VNC Monitor"
Defaultdepth 24
SubSection "Display"
Depth 24
Virtual 1024 768
Modes "1024x768@75" "1280x960@90" "800x600@75" "1280x1024@60" "1280x960@85"
EndSubSection
EndSection
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RumpletonBongworth
Tux's lil' helper
Joined: 17 Jun 2024
Posts: 77
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| Posted: Mon Jun 24, 2024 6:41 pm Post subject: |
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| Taigo wrote: | Oh it seems you're right. But the 160hz doesn't seem usable or specified anywhere.
Also it seems when i was on windows i was using an out of range horizontal synz of 90khz and the monitor did not give me any warning of this. Is it still safe to use and go outside the bounds a little or should i absolutely stay inside that range in the manual. |
Neddy might know better but I think that, if you define the ranges in accordance with the technical specifications and stick to sensible modlines - such as those based on VESA CVT - all should be well. Especially since your CRT monitor is the evolved kind that knows to reject modes that it cannot safely handle. |
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NeddySeagoon
Administrator
Joined: 05 Jul 2003
Posts: 54578
Location: 56N 3W
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| Posted: Thu Jun 27, 2024 5:23 pm Post subject: |
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Taigo,
It's save to push the vertical refresh rate a little but not the horizontal frequency.
It's running the horizontal rate outside (above) the limit that over volts the high voltage parts that are already working near their design limits.
You modelines should appear in in Xorg.0.log now with a reason for rejection, if any.
_________________
Regards,
NeddySeagoon
Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail. |
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