On Saturday, 24 August 2024 14:25:31 BST Alan Mackenzie wrote: > On Sat, Aug 24, 2024 at 10:44:44 +0100, Michael wrote:
> > Instead of resetting the firmware and losing all your MoBo settings, you'd > > be better off to flash the latest firmware on the MoBo. UEFI MoBo > > firmware usually offers the option to back up your settings first. MSI > > support would probably ask you to do this and reset all settings anyway, > > before they deal with any issues. > > I think you're right, there. Unless I've already got the latest firmware > installed (the form to fill in for MSI asked for the firmware version, > which I gave). > > > Do you still get this offset problem if you remove the KVM switch and > > connect the monitor directly to the MoBo? > > I tried that, but got no display signal at all. Maybe I had the wrong > cable plugged into the wrong socket, but I don't think so. There's a > veritable rats' nest of cables behind my PCs which is moderately > difficult to get to. I was able to shut the machine down by logging in > as root blind, and typing shutdown -h now, so the machine defintely came > up. Hmm ... normally you would have a display coming up, if your PC is indeed connected to the monitor. This would be the first thing I would try to make sure I can get a correct display. :-/ > With the new PC connected up through the KVM switch (and also an > HDMI->DVI adapter) I'm still getting the 5cm. gap at the LH side of the > screen. I've installed X and xfce, and that displays poorly, with lots > of flickering, shimmering colour threads through the display. I suspect > my HDMI->DVI adapter may be broken. The display goes blank for several > seconds then comes back again several times a minute. I saw something > like this when I booted KDE from the live-CD a few days ago to see the > firmware files needed. This reads like an unsuitable refresh rate problem. > It's worth noting that my display was also imperfect when I plugged > laptops into it a couple of years back, but not so bad as my xfce is now. > > > What may be happening is the KVM causes some distortion to the signal > > amplitude/frequency, which the monitor interprets as an offset. You could > > try to tweak this by feeding a bespoke EDID to the kernel, but sometimes > > a simple cable swap or operating the KVM a few times can cure it. > > Maybe, but it's all digital, not analog, isn't it? I remember tweaking > timings in .xinit for CRT monitors (a tedious job, indeed), but surely an > EDID signal is either going to be read by the OS correctly, or not at > all? Yes, the processing is digital, but the noise on the wire may not be. I've seen an LED monitor randomly coming up with a lot of distortion on console or DM (SDDM), everything flickering and double image/shading, only for the display to reset perfectly when a Plasma desktop is launched, or after the PC is rebooted. If the handshake between the card and the monitor is incorrect when hardware is initialised, then you'll need a reset of sorts to start again with the correct EDID parameters. > I've already tried swapping the cables to the KVM box, this achieving > nothing. > > > > I'm a bit fed up with all of this. It's a new machine, but the > > > motherboard, an MSI B650 Tomahawk Wifi, has been around a fair while and > > > bugs in its BIOS ought to have been fixed by now. > > > > Well, we don't know if this is caused by a MoBo firmware bug, although the > > quality of firmware often leaves much to be desired. > > We don't know, no, so I have to guess so as to come up with tests to try. > ;-) The firmware on this MB fails to save the boot order when I put the > DVD drive at the start, in front of the NVMEs (which are still called > "hard drives"). Thus the BIOS isn't perfect. > > I'm still pretty sure that when I booted the machine for the first time, > the display was correct. In particular, I remember noticing the offset > after I tried booting with the drm.edid_firmware kernel parameter for the > first time. I expect, but don't know, the embedded kernel drm.edid_firmware codes offer some default resolution sizes and refresh rates. If your monitor prefers e.g. 59Hz as opposed to a default of 60Hz, you could experience the problems you describe above. I was thinking if you can get a correct display coming up with the monitor connected directly to the graphics port, then you can capture the EDID reported by the monitor and feed this to the kernel as an EDID file instead. > I think I should try to update the firmware, and see if that clears the > problem. The latest firmware is 7D75v1J and was released very recently. It deals with a security issue too, so it's advisable using this version sooner or later: https://www.msi.com/Motherboard/MAG-B650-TOMAHAWK-WIFI/support Besides trying the latest firmware, some other things to try: 1. Use a cable with the appropriate connectors at each end. No KVM, no intermediate adaptors, no extensions, nothing-in-between. Then add one thing at a time to see what makes a difference. 2. Try reseting the monitor itself. Usually there is some OSD menu to adjust monitor settings, see if there is a 'Reset Display' or similar option. 3. Check if the monitor display corrects itself by playing with refresh rates using xrandr/xorg.conf/desktop GUI Display settings after you launch xfce. 4. You should not have to do this, but if the KVM consistently throws out the offset then check if the monitor OSD has a screen adjustment submenu to tweak the screen viewport and shift it to fit the monitor. Let's hope one of these things delivers a working display for you. :-)
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