Anyone who's been keeping up will know I finally got my new Win10 Desktop to do pretty well what I want.
It is used with this ancient Acorn via a KVM switch. Video is DVI - since that's about the latest Acorn can do, with a special after market video card. I also split the DVI feed from the DVI KVM switch to the monitor to drive a TV above the workbench when needed - via an DVI to HDMI splitter. Used to get a circuit diagram etc where it can be easily seen.
This all worked perfectly with the old Win7 PC, and have now got it working with the new one - after buying a new video card with a DVI output.
But there is one funny. If I'm using the Acorn, and the PC goes to sleep, waking it up with the KVM switched to it, it reverts to a generic Windows driver, rather than the one for the video card. And display settings only now see the KVM switch, rather than monitor. A re-boot sorts it - but any guesses on how to stop this - other than stopping it going to sleep?
To reach the conclusion about "driver", you would use Device Manager (in the Windows 10 right-click Start button menu). In Device Manager, the "before condition", if you did Properties on the video card entry, it would say NVidia. If you woke the computer and the driver really had changed, it would say "Microsoft Basic Display Adapter".
This is unlikely to happen. It would require the video card to lose power during the session, gain power, then foul up the config info pulled from BAR.
I interpret your description, as a resolution change. You had one resolution before sleeping the computer, now it's selected a different resolution, based on something that happened.
When you mix KVMs and splitters, the "right things" have to happen to the serial interface for the config device on the monitor. The "Real Time" sampling option here, displays the current table.
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Let's take a DVI splitter. Say DVI uses differential lanes, and a "lazy splitter design" grabs a lane and uses one of the signals in a single-ended fashion. The other output grabs the other wire and uses it single-ended. This is tremendously clever.
However, the cleverness stops when they have to decide which DDC/CI clock and data to use for the monitor. In this example, the second monitor provides the config table of resolutions. Whatever resolution the second monitor recommends via its table, the first monitor has to "eat" when it shows up on the cleverly split data lanes.
The KVM has the same handling chore to perform. It must route the DDC/CI to the correct computer, without any of the other computers being aware there is a KVM present. The KVM cannot "glitch" the signal towards the computer, because the computer will attempt a redetect of the DDC/CI table. KVMs which record the table from the monitor end, and play it back on demand to the computer doing the redetect, they will end up with consistent resolution selections.
They also used to make DDC/CI recorders, for devices which presented an inconsistent table from time to time. For around $50, the box had a power supply (tiny 5V source), it had an EEPROM, some buttons for control, and you could connect a projector (YPrPb) to the computer and have the recorder box "lie" to the computer about what resolutions the projector supported. So say the projector (three lasers and DLP) was 1280x1024, yet it had no DDC/CI wired to the VGA connector, the recorder box could be pre-loaded with a 1280x1024 DDC/CI table and then the computer would say "Ah, you're a 1280x1024 computer monitor, here is your signal".
Recorder boxes existed for a number of different connectors, but in this case, I cannot see a reason for using a recorder. Unless some item ("the Acorn") lacks DDC/CI entirely, there's hardly a reason to be buying a recorder to prop up the situation.
Using Moninfo, verify that the computer is presenting what looks like properly pulled tables. And think about what the wiring is supposed to be doing, who is driving the DDC/CI and so on. In the case of the DVI splitter, you could try swapping what is connected to Monitor #1 and Monitor #2 in the above diagram.
DDC/CI is not a multimaster bus, and so hardware toys cannot connect arbitrary things. They have to make a choice as to what gets connected, and you as the user, have to "sniff around" and figure out which connector is master. In the above diagram, Monitor #2 output is the master and is presenting its DDC/CI table for the computer to read. Then Monitor #1 needs a good multisync implementation, to be eating whatever signal is being sent to it.
Your KVM isn't passing through the EDID (DDC) info, so your PC thinks it's connected to an old VGA monitor. Given that it says 'KVM' it suggests the PC is successfully talking to the KVM, but the KVM is giving the wrong answers.
You can get 'EDID emulator' boxes that lie to the PC as to what EDID is attached, eg:
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might avoid that problem - you hook up the monitor to the box and record the EDID. Then you plug the box into the computer and it thinks that kind of monitor is always attached, even when the KVM removes it.
It should be something the KVM does itself, though. Perhaps there's a setting somewhere?
That's what it looks like. But only after the PC wakes up from sleep mode. With it running, I can swap between the two as often as I like without problem.
With the old Win7 PC, if I woke that up without it being selected, it was on the wrong resolution. But could be corrected via display settings.
I used a KVM switch about ten years a to select any one of three computers for the monitor. That was all superseded long ago when I got an Asus 27" monitor with multiple inputs. I only have two computers computers connected now and I do the switching directly on the monitor. The cabling is very much neater.
You have to follow the wiring and figure this out.
Take the monitor you hope to use and connect it *directly* to the computer. Now, use Moninfo, and do a Real Time fetch. Do you get a proper table from the monitor ?
Some monitors in the past, lacked write protect. It was possible to overwrite the EDID and fill it with garbage. "Verifying" the monitor then, is to check that everything about that monitor is normal.
Now, with your various clever devices, you have to figure out why a given item is not passing the table properly. A KVM for example, could scan the monitor, then present copies of the table on the computer side. Each "box" in the path, presents a challenge. What transform does it perform ? Can it foul up ? What does a failure look like ?
Right away, a monitor name of "KVM" says the KVM could not get an EDID from the monitor, and it substituted a nicely formatted, canned EDID table it keeps for special occasions. Now, you have to figure out whether the KVM has a config switch or jumper to be doing this. Or, figure out how the plumbing coming back from the monitor has ruined the EDID info. If your DVI splitter is between the KVM and the monitor, then the DVI only allows one of its two output ports to be driving the EDID function.
This little adventure is a lot like "buzzing wiring", except the function involved is a bit more esoteric and requires more test cases to reach a conclusion. Verifying the monitor actually has an EDID table, is a necessary part of this. The KVM cannot "invent" the correct table for the monitor. and a "1024x768 KVM" table is highly unlikely to make anyone happy.
Buying one of those boxes (sits in-line in a path where the EDID isn't working) is certainly an option, but it helps to understand what is killing your EDID in the first place.
I have done similar with a two way Aten and now 3 off 4 way. ;-)
Yeahbut don't you have to pick up the remote or press the input button on the monitor itself (no so easy if it's out of arms reach), as opposed to just hitting 'ScrlLk-ScrlLk-1-4'?
The problem Dave has been seeing is as has been mentioned elsewhere and likely a clash / lack / contradiction of information going back to the PC from either the KVM switch and the computers themselves.
The more 'automagic' the machine / switch / OS the more likely it will be to suffer this sort of thing.
I have similar between a 40" TV VGA input and a 4 port VGA KVM and a W10 ITX PC I built that has both VGA and HDMI outputs. W10 gets very confused [1], often only outputting on the disconnected HDMI port and not the VGA.
Swap to a smaller TV with VGA and it all works fine.
Not all PC's on that switch support HDMI (ironically the two RPi's do <g>) so I keep to VGA as the L.C.D.
Cheers, T i m
[1] On VGA through the KVM to 40" TV, you get the PC BIOS splash screen, the W10 booting logo and then nothing (as the video output has switched from VGA to HDMI).
Quite. Both my monitors have 'soft touch' input selection. Neither is as easy to use as a couple of keyboard strokes.
Only using the video card DVI output on the PC.
The old PC worked just fine with the same monitor and KVM switch. With the proviso that if you didn't switch to it before waking it up, it selected the wrong resolution, but easily corrected. With this one, the only way to get back to the correct resolution is with a re-boot.
Yeah, and I was only *intending* using the VGA output on my PC, W10 seemed to want to do different (on the big TV, ok on the smaller TV, even with nothing plugged into the PC HDMI port at the time of booting / switching). ;-(
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I think it might be more the 'Old OS' (W7) than PC Dave?
Yeah, I've had that and so (probably like you) make sure you are switched to the newly turned on PC, for a while at least. Mostly it's ok without doing that though.
I'm currently KVM'ing between XP on this Mac Mini, W10 / Mint 18 / Other OS's on another box (swappable drive bay), W10 on a slimline Shuttle and often something I'm playing with, be it a RPi (with HDMI >
VGA adaptor) or a laptop I'm repairing that has a faulty screen etc.
Upstairs I swap between a replacement for the Mac Mini I've been building / testing for a while, a 'TV PC' (that's due to stay there), A PC that should be with my 3D printer (and will be when daughter takes more of her stuff <g>) and anything else I'm working on (for myself or others). ;-)
Daughter has the same with her main desktop PC (that was her step sisters), the Slimline Shuttle NAS (that mostly runs headless) and the last PC she built for herself when she lived here but ended up using a an i3 laptop we were given. ;-)
I have tried all sorts of screen sharing and virtual keyboards but find nothing as flexible / durable / simple as the Aten KVM switches (apart from the very occasional funny). ;-)
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