What motherboard/platform you have ?
What about DVI to HDMI adapter ?
What model of monitor ?

I had tested this on 2 different PCs with a BenQ 1080p panel

However I just switched to a different monitor (1440p Viotek panel) and it works!

Is there something "off spec" about the X800 DVI signal that makes it work with some monitors and not with others?

agent_x007 wrote on 2022-03-19, 18:06:

What motherboard/platform you have ?
What about DVI to HDMI adapter ?
What model of monitor ?

jamesfmackenzie wrote on 2022-03-21, 11:34:

I had tested this on 2 different PCs with a BenQ 1080p panel […]
Show full quote

I had tested this on 2 different PCs with a BenQ 1080p panel

However I just switched to a different monitor (1440p Viotek panel) and it works!

Is there something "off spec" about the X800 DVI signal that makes it work with some monitors and not with others?

agent_x007 wrote on 2022-03-19, 18:06:

What motherboard/platform you have ?
What about DVI to HDMI adapter ?
What model of monitor ?

I connected the video card to capture hardware where I could reliably monitor the resolution and refresh rate

For all VESA graphics modes, the X800 XL will always output 1280x1024p@60Hz over the DVI connector. The underlying resolution is always scaled up to 1280x1024

I'm not super familiar with DVI-supported display modes, but was a bit surprised by this one - it might explain the weirdness with my monitor

Hope this helps someone in the future!

Are all the monitors on which the x800 does not work in DOS capable of resolution/refresh rate combinations that exceed 165MHz in terms of bandwidth ?

My guess is that there is a potential issue with the logic in the x800 BIOS not being able to deal with resolutions in the monitor EDID that require more than what DVI 1.0/first gen HDMI can handle .

It could be similar to this : Re: Widescreen monitors and 4:3 aspect ratio compatibility thread Re: Widescreen monitors and 4:3 aspect ratio compatibility thread

EDIT : To potentially test this, boot the PC with a working monitor and hotplug to one of the non-working ones . If that works, it is likely that a properly programmed EDID emulator could work around the issue.

darry wrote on 2022-03-22, 00:52:

Are all the monitors on which the x800 does not work in DOS capable of resolution/refresh rate combinations that exceed 165MHz i […]
Show full quote

Are all the monitors on which the x800 does not work in DOS capable of resolution/refresh rate combinations that exceed 165MHz in terms of bandwidth ?

My guess is that there is a potential issue with the logic in the x800 BIOS not being able to deal with resolutions in the monitor EDID that require more than what DVI 1.0/first gen HDMI can handle .

It could be similar to this : Re: Widescreen monitors and 4:3 aspect ratio compatibility thread Re: Widescreen monitors and 4:3 aspect ratio compatibility thread

EDIT : To potentially test this, boot the PC with a working monitor and hotplug to one of the non-working ones . If that works, it is likely that a properly programmed EDID emulator could work around the issue.

The non-working monitor is a BenQ RL2455:
https://www.displayspecifications.com/en/model/dba38c4

It supports 1920x1080@60Hz - not sure if that exceeds 165MHz in terms of bandwidth

If I boot with a working monitor and then hotplug into the non-working monitor ... it does work! Some other good news : if I connect through the passthrough interface on my capture card it also works

Thanks for the help! This is definitely a viable workaround! 😎

And thanks for the tip on EDID emulators too - will do some more research

jamesfmackenzie wrote on 2022-03-22, 02:03:

The non-working monitor is a BenQ RL2455: https://www.displayspecifications.com/en/model/dba38c4 […]
Show full quote

darry wrote on 2022-03-22, 00:52:

Are all the monitors on which the x800 does not work in DOS capable of resolution/refresh rate combinations that exceed 165MHz i […]
Show full quote

Are all the monitors on which the x800 does not work in DOS capable of resolution/refresh rate combinations that exceed 165MHz in terms of bandwidth ?

My guess is that there is a potential issue with the logic in the x800 BIOS not being able to deal with resolutions in the monitor EDID that require more than what DVI 1.0/first gen HDMI can handle .

It could be similar to this : Re: Widescreen monitors and 4:3 aspect ratio compatibility thread Re: Widescreen monitors and 4:3 aspect ratio compatibility thread

EDIT : To potentially test this, boot the PC with a working monitor and hotplug to one of the non-working ones . If that works, it is likely that a properly programmed EDID emulator could work around the issue.

The non-working monitor is a BenQ RL2455:
https://www.displayspecifications.com/en/model/dba38c4

It supports 1920x1080@60Hz - not sure if that exceeds 165MHz in terms of bandwidth

If I boot with a working monitor and then hotplug into the non-working monitor ... it does work! Some other good news : if I connect through the passthrough interface on my capture card it also works

Thanks for the help! This is definitely a viable workaround! 😎

And thanks for the tip on EDID emulators too - will do some more research

Happy to help . I have been down that road before .

Actually, the BenQ RL2455 supports up to 1920x1080 at 75Hz according to this https://esupportdownload.benq.com/esupport/ES … 90430120453.pdf , which typically requires >165MHz

All "standard" timings for that resolution require at least 167MHz ( CVT-RBv2) up to over 220MHz (CVT) , as calculated with https://tomverbeure.github.io/video_timings_calculator. We would need a dump of the monitor's EDID to know exactly what timings the monitor advertises . If you want to run at 1920x1080@75Hz (or preferably 70Hz if DOS gaming is of interest ) on the x800, you might be able to use a custom resolution with reduced blanking programmed into an EDID emulator to fit within 165MHz . There is no real way to know if the x800's BIOS would like that or not without trying it . Some Nvidia cards are happy with this, others not . See 70Hz in pure DOS at 1600x1200 (or other) over DVI on an old card (FX5900) with modern monitor is possible and PSA : Fix for EDID issues with modern monitor and Geforce FX 5900 (no picture/crashes) + Siig EDID emulator software

If tweaking 1920x1080 timings >60Hz does not work with the x800, you will have to settle for 1920x1080 @ 60Hz .

EDIT : You can probably use a modified EDID to force the x800 to a 4:3 resolution in DOS if you want to avoid stretching if your monitor does not have an explicit 4:3 mode that works properly .

Good luck and have fun !

darry wrote on 2022-03-22, 06:38:

Happy to help . I have been down that road before . […]
Show full quote

jamesfmackenzie wrote on 2022-03-22, 02:03:

The non-working monitor is a BenQ RL2455: https://www.displayspecifications.com/en/model/dba38c4 […]
Show full quote

darry wrote on 2022-03-22, 00:52:

Are all the monitors on which the x800 does not work in DOS capable of resolution/refresh rate combinations that exceed 165MHz i […]
Show full quote

Are all the monitors on which the x800 does not work in DOS capable of resolution/refresh rate combinations that exceed 165MHz in terms of bandwidth ?

My guess is that there is a potential issue with the logic in the x800 BIOS not being able to deal with resolutions in the monitor EDID that require more than what DVI 1.0/first gen HDMI can handle .

It could be similar to this : Re: Widescreen monitors and 4:3 aspect ratio compatibility thread Re: Widescreen monitors and 4:3 aspect ratio compatibility thread

EDIT : To potentially test this, boot the PC with a working monitor and hotplug to one of the non-working ones . If that works, it is likely that a properly programmed EDID emulator could work around the issue.

The non-working monitor is a BenQ RL2455:
https://www.displayspecifications.com/en/model/dba38c4

It supports 1920x1080@60Hz - not sure if that exceeds 165MHz in terms of bandwidth

If I boot with a working monitor and then hotplug into the non-working monitor ... it does work! Some other good news : if I connect through the passthrough interface on my capture card it also works

Thanks for the help! This is definitely a viable workaround! 😎

And thanks for the tip on EDID emulators too - will do some more research

Happy to help . I have been down that road before .

Actually, the BenQ RL2455 supports up to 1920x1080 at 75Hz according to this https://esupportdownload.benq.com/esupport/ES … 90430120453.pdf , which typically requires >165MHz

All "standard" timings for that resolution require at least 167MHz ( CVT-RBv2) up to over 220MHz (CVT) , as calculated with https://tomverbeure.github.io/video_timings_calculator. We would need a dump of the monitor's EDID to know exactly what timings the monitor advertises . If you want to run at 1920x1080@75Hz (or preferably 70Hz if DOS gaming is of interest ) on the x800, you might be able to use a custom resolution with reduced blanking programmed into an EDID emulator to fit within 165MHz . There is no real way to know if the x800's BIOS would like that or not without trying it . Some Nvidia cards are happy with this, others not . See 70Hz in pure DOS at 1600x1200 (or other) over DVI on an old card (FX5900) with modern monitor is possible and PSA : Fix for EDID issues with modern monitor and Geforce FX 5900 (no picture/crashes) + Siig EDID emulator software

If tweaking 1920x1080 timings >60Hz does not work with the x800, you will have to settle for 1920x1080 @ 60Hz .

EDIT : You can probably use a modified EDID to force the x800 to a 4:3 resolution in DOS if you want to avoid stretching if your monitor does not have an explicit 4:3 mode that works properly .

Good luck and have fun !

Thanks for all the help here! Lots to try 😎