From Newsgroup: comp.sys.acorn.hardware

Is there something specific to Risc OS that makes it dislike KVMs?

I have a two computer setup here, with a W10 PC, and a Fourtress Ra-Pi
running Risc 5.3, using a two port KVM. It's been fine for maybe a year or
so, switching happily between the two computers, but has now started
acting up. When I switch to the PC, everything is fine, but switching back
to the Ra-Pi, I often get a blank screen, or sometimes video but no mouse, requiring me to pull the power on the Pi and start all again, which is
real pain.

I have tried swapping the input ports with no improvement. The windows PC
is fine when I switch back and forth, always coming back, but the Ra-Pi
never does now.

I am looking at replacing the KVM, hoping it will cure the problem, but
why?
--
Stuart Winsor

Tools With A Mission
sending tools across the world
http://www.twam.co.uk/
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From Newsgroup: comp.sys.acorn.hardware

In message <5d09e8554eSpambin@argonet.co.uk>
Stuart <Spambin@argonet.co.uk> wrote:

Is there something specific to Risc OS that makes it dislike KVMs?

I have a two computer setup here, with a W10 PC, and a Fourtress Ra-Pi running Risc 5.3, using a two port KVM. It's been fine for maybe a year or so, switching happily between the two computers, but has now started
acting up. When I switch to the PC, everything is fine, but switching back
to the Ra-Pi, I often get a blank screen, or sometimes video but no mouse, requiring me to pull the power on the Pi and start all again, which is
real pain.

I have tried swapping the input ports with no improvement. The windows PC
is fine when I switch back and forth, always coming back, but the Ra-Pi
never does now.

I am looking at replacing the KVM, hoping it will cure the problem, but
why?

just to test:
What are your screen settings on RPi4?
--
Jean-Michel
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From Newsgroup: comp.sys.acorn.hardware

In article <1bb8310a5d.jmb@jmc.bruck.orange.fr>,
Jean-Michel <jmc.bruck@orange.fr> wrote:

In message <5d09e8554eSpambin@argonet.co.uk>
Stuart <Spambin@argonet.co.uk> wrote:

Is there something specific to Risc OS that makes it dislike KVMs?

I have a two computer setup here, with a W10 PC, and a Fourtress Ra-Pi running Risc 5.3, using a two port KVM. It's been fine for maybe a
year or so, switching happily between the two computers, but has now started acting up. When I switch to the PC, everything is fine, but switching back to the Ra-Pi, I often get a blank screen, or sometimes
video but no mouse, requiring me to pull the power on the Pi and start
all again, which is real pain.

I have tried swapping the input ports with no improvement. The windows
PC is fine when I switch back and forth, always coming back, but the
Ra-Pi never does now.

I am looking at replacing the KVM, hoping it will cure the problem,
but why?

just to test:
What are your screen settings on RPi4?

X1920 Y1080 C16M F60

This is unchanged since I set the Pi up, which was a little while before I brought the PC down from my "den" in the loft", and set it up with the KVM.

Monitor is Samsung F22T350FHU, KVM is un-named.
--
Stuart Winsor

Tools With A Mission
sending tools across the world
http://www.twam.co.uk/
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From Newsgroup: comp.sys.acorn.hardware

On 17/08/2026 20:00, Stuart wrote:

Is there something specific to Risc OS that makes it dislike KVMs?

I have a two computer setup here, with a W10 PC, and a Fourtress Ra-Pi running Risc 5.3, using a two port KVM. It's been fine for maybe a year or so, switching happily between the two computers, but has now started
acting up. When I switch to the PC, everything is fine, but switching back
to the Ra-Pi, I often get a blank screen, or sometimes video but no mouse, requiring me to pull the power on the Pi and start all again, which is
real pain.

Yes there is a long standing issue with the USB stack. My setup is
separate USB and HDMI switches, and every few USB switches the RISC OS
Pi 4 either hangs or has an unrecoverable error.

I had two identical Pi 4s at one stage and it was only which ever one
was running RISC OS that was affected, Linux was always fine.

There was supposedly a fix to the stack, which was mentioned on the ROOL forum, but I have no idea what has happed to it.

---druck
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From Newsgroup: comp.sys.acorn.hardware

On 18 Aug, druck wrote in message
<1161a3l$1ncv2$1@druck.eternal-september.org>:

On 17/08/2026 20:00, Stuart wrote:

Is there something specific to Risc OS that makes it dislike KVMs?

Yes there is a long standing issue with the USB stack. My setup is
separate USB and HDMI switches, and every few USB switches the RISC OS Pi
4 either hangs or has an unrecoverable error.

Specifically the XHCI driver, which is required for the Pi4 hardware, has issues.

There was supposedly a fix to the stack, which was mentioned on the ROOL forum, but I have no idea what has happed to it.

There were a few false dawns, IIRC, but nothing that actually solved the problem.

The issue, as ever, was that the people who could (or would) do the
development couldn't see the problem on their hardware and so could only
guess at fixes, while the people who could reproduce the problem weren't in
a position (for whatever reason) to investigate it at a sufficiently low
level to work out what was happening.
--
Steve Fryatt - Leeds, England

http://www.stevefryatt.org.uk/
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From Newsgroup: comp.sys.acorn.hardware

In article <1161a3l$1ncv2$1@druck.eternal-september.org>,
druck <news@druck.org.uk> wrote:

On 17/08/2026 20:00, Stuart wrote:

Is there something specific to Risc OS that makes it dislike KVMs?

I have a two computer setup here, with a W10 PC, and a Fourtress Ra-Pi running Risc 5.3, using a two port KVM. It's been fine for maybe a
year or so, switching happily between the two computers, but has now started acting up. When I switch to the PC, everything is fine, but switching back to the Ra-Pi, I often get a blank screen, or sometimes
video but no mouse, requiring me to pull the power on the Pi and start
all again, which is real pain.

Yes there is a long standing issue with the USB stack. My setup is
separate USB and HDMI switches, and every few USB switches the RISC OS
Pi 4 either hangs or has an unrecoverable error.

I had two identical Pi 4s at one stage and it was only which ever one
was running RISC OS that was affected, Linux was always fine.

There was supposedly a fix to the stack, which was mentioned on the ROOL forum, but I have no idea what has happed to it.

Thank you, Druck, and Steve Fryatt, for your answers. The thing that
puzzels me is that it has worked satisfactorily, and consistently, for
well over a year and has only now started giving problems. It would appear
from your answers that buying a replacement switch would not necessarily
solve my problems, so I'm not quite sure where to go from here, other than having separate mice and keyboards. Two mice I could live with, but
separate keyboards would be a bit tricky spacewise.

However, before I go tearing everything apart, can I be assured that it is
not a Risc OS video problem, can I switch the HDMI without issues? I do
know that if I try powering the Pi without the monitor connected, it fails
to start, and, when running VA on my PC, if I switch while VA is running,
that won't come back either, although the PC itself is fine.
--
Stuart Winsor

Tools With A Mission
sending tools across the world
http://www.twam.co.uk/
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From Newsgroup: comp.sys.acorn.hardware

On 20/08/2026 09:45, Stuart wrote:

Thank you, Druck, and Steve Fryatt, for your answers. The thing that
puzzels me is that it has worked satisfactorily, and consistently, for
well over a year and has only now started giving problems.

It can be a bit random, I can go weeks without a problem and then have
it crash a several times in a day.

It would appear
from your answers that buying a replacement switch would not necessarily solve my problems, so I'm not quite sure where to go from here, other than having separate mice and keyboards. Two mice I could live with, but
separate keyboards would be a bit tricky spacewise.

You can get wireless keyboards now which have buttons to change between
3 different machines. My Logitech keyboard and mouse came with two
dongles which can be put in two different machines, and they be used
from a 3rd via Bluetooth.

Of course I've got 5 machines on the desk, so use several USB and HDMI switches, plus DisplayLink docks for dual (or triple) monitor support.

However, before I go tearing everything apart, can I be assured that it is not a Risc OS video problem, can I switch the HDMI without issues? I do
know that if I try powering the Pi without the monitor connected, it fails
to start, and, when running VA on my PC, if I switch while VA is running, that won't come back either, although the PC itself is fine.

I used several different HDMI switches with my RISC OS Pi, and there has
never been any problems when switching video.

I actually avoid USB switching most of the time by using RISC OS via
VNC, which is quick enough for using programs such as email and
spreadsheets, even when away from home. I do switch to it for graphic
heavy applications such as Artworks and Photodesk, as the screen update
is vastly quicker.

---druck

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From Newsgroup: comp.sys.acorn.hardware

In message <1166k6f$3dat8$1@druck.eternal-september.org>
druck <news@druck.org.uk> wrote:

I used several different HDMI switches with my RISC OS Pi, and there has never been any problems when switching video.

I actually avoid USB switching most of the time by using RISC OS via
VNC, which is quick enough for using programs such as email and spreadsheets, even when away from home.

I echo what druck wrote there, although I've only used one HDMI switch
(a cheap 5-way one from eBay that I've had for years).

One of my Raspi's pretty much has to be used via VNC as it lives in the
airing cupboard. Access via VNC has never been a problem.

David
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From Newsgroup: comp.sys.acorn.hardware

In article <a9c76f0b5d.DaveMeUK@BeagleBoard-xM>,
David Higton <dave@davehigton.me.uk> wrote:

In message <1166k6f$3dat8$1@druck.eternal-september.org>
druck <news@druck.org.uk> wrote:

I used several different HDMI switches with my RISC OS Pi, and there
has never been any problems when switching video.

I actually avoid USB switching most of the time by using RISC OS via
VNC, which is quick enough for using programs such as email and spreadsheets, even when away from home.

I echo what druck wrote there, although I've only used one HDMI switch
(a cheap 5-way one from eBay that I've had for years).

One of my Raspi's pretty much has to be used via VNC as it lives in the airing cupboard. Access via VNC has never been a problem.

Well, gentlemen, plugging a mouse and keyboard directly into my Pi, and
using the KVM just to switch the video, seems to have eliminated the
problem. I've now got to work out how to accommodate an extra keyboard on
my desk.

I see the Pi hut have quite a nice white keyboard and mouse package, with
a built-in hub, that has a UK keyboard layout for twenty-four quid so I
may go for that.

Thank you all for your contributions.
--
Stuart Winsor

Tools With A Mission
sending tools across the world
http://www.twam.co.uk/
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