Monitor fed by VGA and DVI-D thru KVM

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Can I use a splitter (DVI-I to DVI-D & VGA) on my monitor (Philips
200W6), and attach a KVM switch, so I can I pump either VGA or DVI
from the KVM and have monitor auto-select the input?

[LCDMonitor -- Philips 200W6]
       DVI-D    VGA
         |       |
[KVM switch -- TRENnet TK-404KR]
   |      |      |      |
   |      |     VGA    VGA
  PC     PC      |      |
                PC     PC

Here's why: I have a VGA HD15 D-sub KVM now. I just built a fast
system with DVI, and bought a 1680x1050 LCD monitor. So, I'd like to
feed the LCD with DVI from my two most used systems, but VGA from my
two older systems.

The trouble with plugging in the new DVI box into the DVI input and
the VGA KVM into the VGA input is... switching the input manually on
the Monitor takes 12 menu button pushes, AND having multiple VGA
signals means that I have to adjust the phase every time I switch VGA
inputs (phase is out of whack). To solve this second problem I would
put a DVI video card into my second most used system, so VGA would be
used only on the 3rd and 4th PCs.

The Philips 200W6 has two inputs: DVI-D and VGA. It will auto-sense
and switch inputs if the active signal goes away. So if I feed DVI-D
and VGA from a splitter cable, they monitor should auto-sense and
switch inputs, right?

I just need to know if I can put a splitter cable on the two Philips
inputs -- such as this one
-- and plug that into a DVI-I KVM switch without frying the monitor.

This is the KVM I would use:

Is this splitter setup commonly used (known to work) or am I breaking
new ground?

(Please excuse the 'burp' when replying (b))

Re: Monitor fed by VGA and DVI-D thru KVM

Reality folded in on itself, and somewhere the following words from
"Jaz" appeared in history:

Quoted text here. Click to load it


DVI/VGA adapters don't convert anything they just re-wire things, but
if you find the right VGA to DVI-I cable it may work out. You will have
to double check with the maufature to see if the KVM is Dual-Link
(switches both analog and digital) and use dual-link cables between the
KVM and any adapters you use (that is a VERY SHORT DVI-I adapter).

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 Lossing quality sleep to help others online since 1997...

Re: Monitor fed by VGA and DVI-D thru KVM

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I think dual-link refers to two digital channels, doubling the DVI-D
data rate. Read more here:
There's also some good info here:

And yes, I need the KVM to carry analog as well as digital -- the
specs say : "DVI-I & DVI-D Compliant". And no, no conversion at here,
just proper adapters and cables.

I think the concept is sound, I'm just looking for people who have
done this so I know it will work with the right hardware.

(Please excuse the 'burp' when replying (b))

Re: Monitor fed by VGA and DVI-D thru KVM wrote:

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The Trendnet folks are careful in that advert, not to mention VGA.
You can _plug_ a DVI-I signal into the box, but I suspect only
the digital portion is handled by the Trendnet product.  I think
the analog portion is ignored. In other words, the two right hand
PCs are not going to get their VGA signals through the Trendnet

If you equip the two right hand PCs with VGA to DVI converter
boxes, then I suspect the Trendnet product you have selected,
would be the right one.

For example, this is the first VGA to DVI converter I found. This
one handles up to 1600x1200 and costs $299. Buy two of those
boxes, plus your Trendnet 4 port DVI box, and you have an
"all digital" solution.

$299 would buy a pretty decent replacement video card :-)


Re: Monitor fed by VGA and DVI-D thru KVM (Paul) wrote:
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I spoke to TRENDnet today and they said "DVI-I is analog and digital
so the TK-404KR does support both (DVI-I and DVI-A)." I was sure to
drive the point home that I would need it to pass the analog signals
over DVI-I. The tech checked with 2nd teir support twice and verified.
So the question is whether this splitter setup between the KVM out and
the two monitor inputs will do what I'm suggesting.

(Please excuse the 'burp' when replying (b))

Re: Monitor fed by VGA and DVI-D thru KVM wrote:

Quoted text here. Click to load it

These are the only reviews I can find:

OK, Let's try this another way. Pretend the product implements
switching with mechanical relays. There are some very nice
miniature RF relays that could be used to route signals.

What such a box would lack, is translation from one standard
to another. Considering the price is $150, about all they
could afford to put in there is some relays. The box
topology would look like this:

            VGA_Out_Pins         DVI_Out_Pins
                 |                    |
                 |                    |
              (relays)             (relays)
             /  | |  \             /  | |  \
             |  | |  |             |  | |  |
         Four comps' VGA pins    Four comps' DVI-D pins

What this would mean to you, is when you switch from a
VGA output computer, to the DVI-D output computer, you
still need to visit the Philips 200W6 and switch it
between the digital and analog input connectors.

I cannot buy that the Trendnet box is able to convert,
in an arbitrary manner, digital or analog input on any
of the four channels, into any old digital or analog output
standard. Translating from digital to analog formats or
vice versa, is not free, and has a significant parts cost.
It would be easier, for the Trendnet box to support
two separate networks, one for the VGA analog signals,
and another for the digital TMDS diff pairs, but four channels
of translation from one standard to the other cannot be
included for a $150 retail box cost.

Just my best guess,

Re: Monitor fed by VGA and DVI-D thru KVM (Paul) wrote:
Quoted text here. Click to load it

No, I think you've read me all wrong. What I mean to do is simply
route the vga and dvi signals over their respective paths...

A VGA 15-pin d-sub cable carrys only an analog signal; the VGA input
on the monitor only accomodates analog.

The monotor's DVI-D input only accomodates digital (it is void of the
analog pins).

The KVM switch is equiped with DVI-I, which is both analog AND
digital, by rights of having paths for all the pins on a DVI-I cable
(analog and digital are carried on separate pins/wires). The TRENDnet
folks have told me that it works with both digital and analog.

Therefore, if the KVM is switched to a PC supplying VGA, then there
should be a signal on ONLY the VGA pins of the KVM DVI-I out. And, by
switching to a PC supplying DVI-D, there should be a siganl on ONLY
the digital pins of the DVI-I out.

Now, use the splitter cable I mention above, and as I switch between
VGA and DVI-D PC, the video signal switches between the VGA and DVI-D
sides of the splitter. Since there would be a signal on only one at a
time, the monitor should do the input switching for me.

One last thing, when I mentioned "adapters" I was only referring to a
connector format change from 15-pin d-sub to DVI-I. This simply lets
me plug a VGA cable into a DVI-I port on the KVM switch. These
adapters are everywhere -- one comes included with almost all DVI
video cards.

Frankly, this discussion is helping gain confidence that this will
work, so I'm going to place the order asap. Also because if this
doesn't work then I'm going to need a different monitor -- one that
has dedicated input select buttons.

And please! Correct me if I'm wrong! :)
(Please excuse the 'burp' when replying (b))

Re: Monitor fed by VGA and DVI-D thru KVM wrote:

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OK. We seem to be in agreement :-)

I guess the advertising text's insistence on not mentioning
VGA is what put me off.

The remaining thing that bothers me a bit, is what will
happen to the DDC signals. There is a DDC clock and data
digital signal, coming from the computer to the monitor.
One of four computers will be selected, on the computer
side of the Trendnet, which is fine. No problem there.

On the monitor side, your splitter cable presumably will
put the same DDC_clock and DDC_data signal, on both
the analog and digital connectors on the monitor. The
monitor should not really connect these signals
together, because the monitor designer assumes two independent
computers are driving the monitor analog and digital
connector. That means the monitor will be queried for
EDID information by both connectors at the same time.

I believe the technology, is an I2C bus, and I think
that is open collector. There would be no damage to
the monitor with the DDC_data pins wired together
(open collector logic is inherently safe against
that kind of fault). The computer end may become confused
about the available resolutions supported by the monitor,
if there is a conflict between the two data pins
driving the same DDC_data. Maybe if the bus
address decode on the two connectors were different,
then only one of the two DDC_data pins would respond
with EDID information. So it might just magically work,
and as I don't own any VESA standards, I cannot guess
at the details of their implementation of I2C. (clock and data pins) (data exchanged)

I don't think this is a big deal, but if you notice that
either your VGA or your DVI-D computers, don't seem to know
the declared monitor type (they see it as "Default" or
something), then you'll have some idea why it is happening.

If the splitter cable routes the DDC signals to only one
of the two connectors, then two of the computers would
not get monitor type and resolution data.

It might be a minor nuisance, but everything else should work.


Re: Monitor fed by VGA and DVI-D thru KVM (Paul) wrote:
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By George, er... Paul, I thnk you've got something! I don't have time
to research this now, 'cept to say that this is cable I'm looking at:
Now, Lindy's description for this cable is just what I'm proposing to
do! I didn't know about this page until now, so I'm excited to have
come accross it.  

More later... and thank you Paul.
(Please excuse the 'burp' when replying (b))

Re: Monitor fed by VGA and DVI-D thru KVM

Reality folded in on itself, and somewhere the following words from
"Jaz" appeared in history:

Quoted text here. Click to load it

Just to add to Paul's comments, at the "bolts" side of things as it
where... The adapters that DVI-I cards have a male DVI-I connector
with a female sub-D VGA at the other end, so to put it bluntly *the
genders don't match there mate.

Simple Rules:
 - Video cards have female connectors
 - Monitors have male connectors
 - Video cables only go in one direction

This was origonaly done to differentate serial ports from video ports
back in the CGA days, since they used the same style connectors.

Video have as evolved since then but the gender diffrences remain.

That said, there are DVI-A cables out there that may work; thay have
a  male VGA connector at one end and a female DVI-A connector at the
other... But I don't know if they have nay issues...

 __ __| |            __ __|           |    __  /
    |     \    -_)      |   -_)   _|    \     /    -_)   _| _ \
   _|  _| _| \___|     _| \___| \__| _| _| ____| \___| _| \___/

 Lossing quality sleep to help others online since 1997...

Re: Monitor fed by VGA and DVI-D thru KVM

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Most HD15 VGA cables seem to be Male-Male. Some KVM switches are Male
(Tripplite) which require a M-F cable, but...  Anyway, I beliave all
video cables are functionally bidirectional -- if the gender doesn't
match then a gender-changer is in order.

I spoke with a very knowledgable fellow at Lindy Computer Connection
Technology Inc, specifically about their #41219 cable, and they said
that what I'm trying to do should work, at least with their own KVM.
They also said that the generic DVI-I-to-HD15(vga) adapters that you
typically use for changing a video card's DVI-I output to HD15 for
your VGA monitor, are bidirectional, and should 'do the right thing'
on the KVM's output (testing using a VGA monitor -- without the

I hope this is true, since I can imagine there could be lots of issues
with various signals like you describe, such as monitor type/
manufacturer, etc. Certainly this could be be the culprit. Any takers?

Over the past week I emailed and phoned TRENDware to get the final
word on whether this is a digital-only or analog/digital switch, and
they maintain that it's indeed DVI-I analog/digital. I asked if it's
possible that something might have been lost in translation with the
Taiwanese manufacturer's specification sheet and that it may not
actually be DVI-I, but DVI-D instead. They said 'No'. Hmmm... I
suppose that aside from cabling problems, it's possible that my switch
is faulty and needs to be replaced.

Another problem I see is with the DVI source PC -- it starts up in
analog mode if that port is not active at boot-up. Sheesh! Is there no
end to these issues?! Might this be a shortcomming of the DVI
standard? Shouldn't the KVM switch provide the needed signal to the
DVI source so that it doesn't default to VGA mode? (and because this
KVM doesn't pass analog, the monitor is blank).

Well, perhaps the best thing to do at this point is to go all DVI-D/I.
The reason I didn't in the first place is that two of the old PCs
simply don't have the option of changing cards (built-in VGA) -- they
have needed stuff on them I and don't want to spend the effort in
moving application and data to new systems.

(Please excuse the 'burp' when replying (b))

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