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?

--
*Income tax service - We‘ve got what it takes to take what you've got.

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman wrote:

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

That sounds unlikely, are you sure the GPU isn't just switching to a
default resolution, because it can't get EDID data from the monitor?

rather than the one for the video card. And display settings only
now see the KVM switch

Is the KVM one wit enough intelligence to remember the EDID data from
and replay it to the PC when another input is connected to the monitor?

Have you somehow swapped KVM or HDMI splitter ports around in all the
changes?

Dave Plowman (News) wrote:
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.

https://www.entechtaiwan.com/util/moninfo.shtm

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.

clever DVI
splitter
Computer ----------x x------- DDC/CI Monitor #1
\________
\
x------- DDC/CI Monitor #2

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.

Paul

In article ,
Paul wrote:
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.

If I look at display settings, there is only a choice of two - both
ancient 4:3 ones, with this condition. And instead of the monitor name,
says KVM.

--
*Women like silent men; they think they're listening.

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote:
In article ,
Paul wrote:
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.

If I look at display settings, there is only a choice of two - both
ancient 4:3 ones, with this condition. And instead of the monitor name,
says KVM.

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:
https://www.ebay.co.uk/itm/Gefen-DVI...e/133363100740
which 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?

Theo

On 28/08/2020 21:24, Theo wrote:
"Dave Plowman (News)" wrote:
In article ,
Paul wrote:
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.

If I look at display settings, there is only a choice of two - both
ancient 4:3 ones, with this condition. And instead of the monitor name,
says KVM.

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:
https://www.ebay.co.uk/itm/Gefen-DVI...e/133363100740
which 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?

Theo


I use two PCs at the moment with a very basic KVM. (Aten CS22U) One PC
is W10 and the other is XP. It just works, I'm afraid.

I realise that this is no help at all with your issue, but I thought it
might give you hope.

On Fri, 28 Aug 2020 23:01:38 +0100, GB wrote:

On 28/08/2020 21:24, Theo wrote:
"Dave Plowman (News)" wrote:
In article ,
Paul wrote:
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.

If I look at display settings, there is only a choice of two - both
ancient 4:3 ones, with this condition. And instead of the monitor
name,
says KVM.

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:
https://www.ebay.co.uk/itm/Gefen-DVI...Store-Instant-
Switching-problem-solving-device/133363100740
which 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?

Theo


I use two PCs at the moment with a very basic KVM. (Aten CS22U) One PC
is W10 and the other is XP. It just works, I'm afraid.

I realise that this is no help at all with your issue, but I thought it
might give you hope.


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.

On 28/08/2020 23:01, GB wrote:
On 28/08/2020 21:24, Theo wrote:
"Dave Plowman (News)" wrote:
In article ,
Â*Â*Â* Paul wrote:
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.

If I look at display settings, there is only a choice of two - both
ancient 4:3 ones, with this condition. And instead of the monitor name,
says KVM.

Your KVM isn't passing through the EDID (DDC) info, so your PC thinks
it's
connected to an old VGA monitor.Â* 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:
https://www.ebay.co.uk/itm/Gefen-DVI...e/133363100740

which might avoid that problem - you hook up the monitor to the box and
record the EDID.Â* 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.Â* Perhaps there's a
setting somewhere?

Theo


I use two PCs at the moment with a very basic KVM. (Aten CS22U) One PC
is W10 and the other is XP. It just works, I'm afraid.

Aten KVMs are usually considered to be fairly decent kit (with prices to
match), so you would expect them to get it right.



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article ,
Theo wrote:
"Dave Plowman (News)" wrote:
In article ,
Paul wrote:
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.

If I look at display settings, there is only a choice of two - both
ancient 4:3 ones, with this condition. And instead of the monitor name,
says KVM.

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.

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.

You can get 'EDID emulator' boxes that lie to the PC as to what EDID is
attached, eg:
https://www.ebay.co.uk/itm/Gefen-DVI...e/133363100740
which 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?

I'll see if I can find the instructions.

--
*Money isn‘t everything, but it sure keeps the kids in touch

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote:
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.

When the PC wakes from sleep it'll rescan the monitors, because you might
have unplugged something while it was sleeping. It looks like the KVM keeps
telling the PC there is a monitor connected even when you switch away from
that input (as it should, to avoid unnecessary window rearrangement) while
the PC is running, but when the PC awakens it does a full rescan and decides
it can't make sense of what's attached and so falls back to classic VGA.

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.

Sounds like a similar problem.

You might also be able to force the PC to output a specific resolution
irrespective of what the monitor/KVM says. It's a bit like installing a
Monitor Definition File on your Acorn. I've done that on Macs and Linux but
I'm not familiar with how Windows does it. There's probably an app for
that.

Theo

Dave Plowman (News) wrote:
In article ,
Paul wrote:
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.

If I look at display settings, there is only a choice of two - both
ancient 4:3 ones, with this condition. And instead of the monitor name,
says KVM.


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.

Paul