8800gt to hdtv dvi splitter question

Please forgive if this has been asked before but I'm not finding a consensus
yet.

I have a 37" HDTV and just bought a dvi to hdmi cable so I can hook my
computer up to the TV.

Currently I am using a 8800gt (on a XP computer) with a dual monitor
setup...so both dvi ports are being used. I would like to not have to keep
crawling behind the computer to plug in the TV Dvi cable. I saw there are
DVI splitter Y cables which would be nice as I can keep the TV cable plugged
in all the time to the second DVI port...along with my second computer
monitor, but I'm reading somplaces that there might not be enough
"power...or some confusion" to have both my second monitor and HDTV running
at the same time off one DVI port on the 8800?

Thanks for any help. It's not a huge deal to keep crawling behind the
computer to hookup but seems like it would be more convenient to not to have
to.
M

--




Photoshop Retouching & Digital Artwork
www.PixelKat.com

"Michael" wrote in message
...
Please forgive if this has been asked before but I'm not finding a
consensus yet.

I have a 37" HDTV and just bought a dvi to hdmi cable so I can hook my
computer up to the TV.

Currently I am using a 8800gt (on a XP computer) with a dual monitor
setup...so both dvi ports are being used. I would like to not have to
keep crawling behind the computer to plug in the TV Dvi cable. I saw
there are DVI splitter Y cables which would be nice as I can keep the TV
cable plugged in all the time to the second DVI port...along with my
second computer monitor, but I'm reading somplaces that there might not be
enough "power...or some confusion" to have both my second monitor and HDTV
running at the same time off one DVI port on the 8800?

Thanks for any help. It's not a huge deal to keep crawling behind the
computer to hookup but seems like it would be more convenient to not to
have to.
M

Should not be an issue...the splitter on one DVI output would simply give
two identical displays.....you'd need to switch to 1080P resolution or
whatever your HDTV is (720P or 1080i)when using the HDTV.

Michael wrote:
Please forgive if this has been asked before but I'm not finding a consensus
yet.

I have a 37" HDTV and just bought a dvi to hdmi cable so I can hook my
computer up to the TV.

Currently I am using a 8800gt (on a XP computer) with a dual monitor
setup...so both dvi ports are being used. I would like to not have to keep
crawling behind the computer to plug in the TV Dvi cable. I saw there are
DVI splitter Y cables which would be nice as I can keep the TV cable plugged
in all the time to the second DVI port...along with my second computer
monitor, but I'm reading somplaces that there might not be enough
"power...or some confusion" to have both my second monitor and HDTV running
at the same time off one DVI port on the 8800?

Thanks for any help. It's not a huge deal to keep crawling behind the
computer to hookup but seems like it would be more convenient to not to have
to.
M


First of all, DVI and HDMI use differential signals. For signals names
and details, you can use this Wikipedia article as a starting point. The
picture below is shown for just one of the signal pairs on the connector.

( http://en.wikipedia.org/wiki/Digital_Visual_Interface )

______
D+ ___| |_______

___ _______
D- |______|

______ +1
(Receiver | | 0
difference) ___| |_______ -1

Differential uses two wires. The signals are the
inverse of one another. The device receiving them, takes the
difference between them. This gives double the amplitude, and
more importantly, can make it possible to analyse the signals
without relying on a ground reference in an absolute way. The
ground on the cable might be sensitive to ground currents
flowing between pieces of equipment, so some avoidance of
relying on the ground is a good thing.

Now, if I was a cheapskate manufacturer, I could try something
like this. I could take the source signals, and drive two connectors.
Each receiver sees half the normal amplitude. (There may be
another way to do this, but this has a certain attraction to
it. It is easy to make, and cheap.)

______
D+ ___| |_______ \
\___ to DVI display #1
GND __________________ /


GND __________________ \
\___ to DVI display #2
___ _______ /
D- |______| /

I don't know for a fact, that this is how they would do a
passive splitter. But it is an obvious choice. The
result is each differential receiver inside the display,
sees half the normal amplitude. If the amplitude budget
is not used up, it may even work. One consequence could be,
that the max length of cabling for the displays is
severely limited. Too long a cable could give
"colored snow" or loss of sync.

*******

They also make active devices, that make good copies
of the input signal. This box uses an external power
supply, to power the chip inside the box.

http://www.gefen.com/pdf/EXT-DVI-142SL.pdf

When you read that manual, the manual also addresses another
issue. There are some control functions on DVI, which won't
particularly like two displays connected to one computer
output. The resolution options offered by the display
devices, could be different. The Gefen device seems to wire
the DDC/CI resolution information from Display #1, back to the
computer. So the characteristics of Display #1, is how the
Display Control Panel in the OS, will be selecting and
offering resolution choices. If the second display
cannot handle a resolution choice made, the screen
may go blank on that display. (Modern LCDs at least,
can protect themselves against illegal resolution
choices.)

The second issue would be HDCP. What I can't tell you,
is if the protocol used, would cause both displays to
use the same decryption key and recover an encrypted
signal. If may mean that if you attempted to view a
movie in Vista, that one display would not work. I don't
know enough about HDCP to tell you what would happen
in that case.

The passive cable will have similar issues, except
we won't even have a manual to consult, to tell us
what to expect.

The Gefen product is absurdly expensive. Which makes
flipping cables a very attractive option. You can try the
passive cable scheme if you want, but no guarantees
about signal quality.

The above is just a guess on how the passive cable works.

Good luck.

Paul

1) Customer reviews of the DVI splitter cables are mixed. Your milage may
vary.

http://www.amazon.com/Cables-Unlimit...DateDescending
http://www.newegg.com/Product/Produc...82E16882339131
http://www.newegg.com/Product/Produc...82E16812339004

2) If you want a greater probability of success, use a powered splitter box
which amplifies and "reclocks" the DVI outputs.
http://www2.dvigear.com/dvi1x2.html

3) The best solution may be to simply pick up a second, low-cost video card
to drive the TV. A $30 8400GS will happily co-exist with your 8800GT and
drive any-sized TV or display.
http://www.newegg.com/Product/Produc...82E16814162026
They even make PCI versions of this card if you lack a second PCIe x16 slot.
http://www.newegg.com/Product/Produc...82E16814187041

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It can therefore be said that politics is war without
bloodshed while war is politics with bloodshed."

"Michael" wrote in message
...
Please forgive if this has been asked before but I'm not finding a
consensus yet.

I have a 37" HDTV and just bought a dvi to hdmi cable so I can hook my
computer up to the TV.

Currently I am using a 8800gt (on a XP computer) with a dual monitor
setup...so both dvi ports are being used. I would like to not have to
keep crawling behind the computer to plug in the TV Dvi cable. I saw
there are DVI splitter Y cables which would be nice as I can keep the TV
cable plugged in all the time to the second DVI port...along with my
second computer monitor, but I'm reading somplaces that there might not be
enough "power...or some confusion" to have both my second monitor and HDTV
running at the same time off one DVI port on the 8800?

Thanks for any help. It's not a huge deal to keep crawling behind the
computer to hookup but seems like it would be more convenient to not to
have to.
M

--




Photoshop Retouching & Digital Artwork
www.PixelKat.com