Thomas said:
XP SP2
I have a Dell Precision M6300 laptop with a docking station that is
connected to two LCDs. Right now, I can only use two screens at a
time--either the laptop screen and one LCD, or both LCDs without the laptop
screen. I would like to use all three screens at the same time. According
to Dell, the laptop does not support the use of more than two screens at a
time.
I am wondering if there is a software or hardware solution that would allow
me to use all three screens at the same time. Does anyone know how this
might be done?
--Tom
A resolution dependent solution, is the usage of a Matrox DualHead2Go
or a TripleHead2Go. These are devices, that take input from the existing
video connection, and split the image to fit two monitors. For example,
the DualHead2Go does this. The laptop is fooled into thinking the monitor
is "extra wide", and then the hardware splits the pixmap between
two monitors. One video output becomes two video outputs.
+------------------+ +-----------+ +-----------+
| 2560x1024 | ===> | 1280x1024 | + | 1280x1024 |
| | | | | |
+------------------+ +-----------+ +-----------+
It looks like I've lost count of the number of versions available
for that product. The basic principle is the DualHead2Go takes
something like 2560 and makes two 1280 images. The TripleHead2Go
takes 3840 and makes three 1280 images. In the Newegg advert, I
notice that other output resolutions are now supported (some of
those choices weren't offered with the first generation).
Matrox has some web pages, that give compatibility information.
The graphics device in the laptop is programmable, but will
have some upper limit as to the horizontal resolution it will
support. Matrox has tested a number of these devices, to
determine what they are capable of. Not all OSes are supported
(the software installed with the product, is used to control
the GPU and make the odd resolution available - I don't think it
has to do much more than that).
http://matrox.com/graphics/en/support/gxm_main/
They are offered for sale on Newegg, so you can read the
customer reviews there, as to how well it worked out.
Anandtech has also had a review or two, of the product.
TripleHead2Go comments - VGA or DVI in, triple DVI out
DVI input is dual link capable (and not all DVI sources
will be capable of that).
http://www.newegg.com/Product/ProductReview.aspx?Item=N82E16815106011
DualHead2Go comments - this one seems to be VGA in and two DVI outputs ?
http://www.newegg.com/Product/ProductReview.aspx?Item=N82E16815106016
DVI digital would be the best format for input, but not if your
laptop is not dual link capable. VGA is analog and the
quality is subject to the quality of the DAC on the GPU, the
EMI filters on the VGA outputs, the VGA cable itself, and any
of those can degrade the image. The digital part of DVI on
the other hand, can do the job without degradation (until you
use too long a cable).
(Some background here on DVI and dual link - determining whether
dual link is available on a product is difficult, and it usually
not prominently mentioned in adverts. And just because the
connector "is full of pins", doesn't mean it has dual link
output - they'll use whatever connector they feel like, even
if not all the pins are wired up.)
http://en.wikipedia.org/wiki/Digital_Visual_Interface
A typical approach, would be to investigate the compatibility issues
first, at the Matrox end. And then buy monitors which can be driven
at their native resolution, for best results. For example, say
the Matrox could only output 1280x1024 - you wouldn't want to send
that to a 1680x1050, as the monitor would have to resample the
image, and the aspect ratio would be off. Some planning has to
go into the whole process, for best results.
*******
The above uses your built-in GPU for all output. Your
GPU has a high bandwidth connection to the rest of the
computer, so is best able to render bitmaps (like video)
without grunting too hard.
You can get add-in devices like this. But remember that
the PCCard interface has limited bandwidth, so if a
program insists on redrawing its window over and
over again, this interface may be "laggy" in comparison
to when the window is moved to your other screens.
And I don't know if anyone makes an Expresscard version
of something like this or not.
http://www.villagetronic.com/vtbook/index.html
On the USB2 bus, companies have been making half-baked
products there for some time. If you attempted
video playback on that screen, chances are the quality
would not be that good (laggy). New models of these types
appear all the time, and I picked this at random just
to illustrate the concept. This one claims 1280x1024
output. It may not use data compression for pumping
data to the screen.
http://www.iogear.com/product/GUC2015V/
I think Samsung even incorporated something like that
into one of their monitors - the monitor comes with a USB2
connector on the back, for the video connection.
You can read the article here, for details about
the software it auto-installs, and the compression
method used and so on. There is limited OS support.
http://www.xbitlabs.com/articles/monitors/display/samsung-sm940ux.html
So for the USB2 products, there may be slight differences
in how slow your "slide show" ends up being. The Matrox
products make the best of a bad situation, but do
require lots of careful research before purchase.
After all, you could pour a bucket-load of cash into
the Matrox approach.
Paul
