Question on DVI & video cards

[Jethro]

I just bought a LCD flat screen monitor, and of course it has DVI
input capability. That requires a special cable, which I have. I
presume now, that I have to buy a video card to make the cable
connectible to my machine.

I presume that I can buy either a AGP of a PCI video card with such a
capability. My concern is - how can I know if my MOBO can handle such
a card or cards? Before I spend my money, that is. Or is that a
concern?

Thanks

Jethro

 

[Paul]

I just bought a LCD flat screen monitor, and of course it has DVI
input capability. That requires a special cable, which I have. I
presume now, that I have to buy a video card to make the cable
connectible to my machine.

I presume that I can buy either a AGP of a PCI video card with such a
capability. My concern is - how can I know if my MOBO can handle such
a card or cards? Before I spend my money, that is. Or is that a
concern?

Thanks

Jethro

For PCI, I cannot think of a reason a card would not work. (Well, maybe
if you had a server board with some 3.3V only slots or something, but
your desktop board is not likely to cause a problem.)

For AGP, you can read this. The tables are not complete, because the
newer AGP cards haven't been added. And for any cards not shown, you
can look at a photograph of the card, and examine the card for the
keying info on the edge connector of the card.

http://www.playtool.com/pages/agpcompat/agp.html

If you buy a high performance card (for gaming), then you'd
also want to check that the power supply is big enough to run
the card. For example, while this is a PCI Express card, the
new 8800GTX draws 145W while gaming. Some other Nvidia cards
only draw 20-30W, which is nothing by comparison. If the card
you buy only costs $50, it isn't likely to overload the power
supply. To work out an exact answer, requires a hardware
inventory of what is in the computer, and which card you
are going to buy.

http://www.techpowerup.com/gpudb/

(This site is where I get power info - these are some high power
PCI Express cards. For recent AGP cards, info may be harder to
find, but you can approximate by looking at PCI Express cards
that happen to use the same GPU.)

http://www.xbitlabs.com/articles/video/display/gf8800_11.html

Paul

 

[Jethro]

For PCI, I cannot think of a reason a card would not work. (Well, maybe
if you had a server board with some 3.3V only slots or something, but
your desktop board is not likely to cause a problem.)

For AGP, you can read this. The tables are not complete, because the
newer AGP cards haven't been added. And for any cards not shown, you
can look at a photograph of the card, and examine the card for the
keying info on the edge connector of the card.

http://www.playtool.com/pages/agpcompat/agp.html

If you buy a high performance card (for gaming), then you'd
also want to check that the power supply is big enough to run
the card. For example, while this is a PCI Express card, the
new 8800GTX draws 145W while gaming. Some other Nvidia cards
only draw 20-30W, which is nothing by comparison. If the card
you buy only costs $50, it isn't likely to overload the power
supply. To work out an exact answer, requires a hardware
inventory of what is in the computer, and which card you
are going to buy.

http://www.techpowerup.com/gpudb/

(This site is where I get power info - these are some high power
PCI Express cards. For recent AGP cards, info may be harder to
find, but you can approximate by looking at PCI Express cards
that happen to use the same GPU.)

http://www.xbitlabs.com/articles/video/display/gf8800_11.html

Paul

Paul - thank you for very definitive information. I will certainly
look things over. After I made the post, I suddenly realized that I
have a KVM problem as well. Of course my KVM now does not have DVI.
Also, I have a AGP video card in one machine and on-board video in the
other.

Maybe I'll get bak to U when I research this some more

Thanks again

Jethro

 

[USR]

Paul - thank you for very definitive information. I will certainly
look things over. After I made the post, I suddenly realized that I
have a KVM problem as well. Of course my KVM now does not have DVI.
Also, I have a AGP video card in one machine and on-board video in the
other.

Maybe I'll get bak to U when I research this some more

Thanks again

Jethro

All you need is a DVI to VGA adaptor ... costs less then $10.

 

[Jethro]

All you need is a DVI to VGA adaptor ... costs less then $10.

Hmmm - I must not understand.

If I get a DVI2AVI adaptor and thereby connect my LCD to the KVM via
my DVI-D cable, would the video performance be same, better, or worse
than I have now by connecting the LCD to the KVM with straight VGA
cable?

Thanks for response

Jethro

 

[Paul]

Hmmm - I must not understand.

If I get a DVI2AVI adaptor and thereby connect my LCD to the KVM via
my DVI-D cable, would the video performance be same, better, or worse
than I have now by connecting the LCD to the KVM with straight VGA
cable?

Thanks for response

Jethro

I think he is thinking of a DVI-I dongle plug, which extracts the VGA
signals on a video card DVI-I connector, and puts them on the familiar
15 pin VGA connector. There is no conversion process in there.
What you wanted, was the DVI digital signals, which are immediately
available on a DVI connector.

DVI is digital signalling. VGA is analog signalling. Generally, the
conversion between the two formats is expensive, because it involves
D2A or A2D conversion. For example, you could use a VGA video card,
a VGA only KVM, then use one of these for final conversion from
VGA format to DVI digital for your DVI-only monitor. Trouble is,
this converter is $300. Gefen is the Cadillac of the industry,
so you may find a better price from some Taiwanese knockoff
(but the Gefen does support a wide range of resolutions, a plus).

http://www.gefen.com/kvm/product.jsp?prod_id=1310

When shopping for an LCD monitor, I would either buy a VGA-only
monitor (like the one I'm typing on), or a dual input unit
having both DVI and VGA inputs (usually more expensive). I
would never consider a DVI digital only monitor, for the
very reasons you are discovering. A DVI digital only monitor sits
on a technology "island" - in an environment with legacy
equipment, you want a monitor with a bit more flexibility.

I have seen a KVM which has both DVI and VGA inputs on it.
But, as far as I know, they come out the other side, as a
DVI network and a VGA network. You need a dual monitor which
can detect the active input, to get maximal efficiency from
such a (dual output) KVM. The KVM doesn't convert between
formats, and simply switches whatever input it gets, to the
appropriate output for the signal type. The switching function
is easy to do, and doesn't cost money - a device like this
should be dirt cheap. But you need a monitor with both input
connectors, plus the monitor must switch automatically between
live inputs (which some monitors refuse to do). I read a rant
from one poster, who was doing something like this, and he
had to use the monitor OSD, to switch between DVI and VGA,
and it was driving him nuts.

DVI plug #1\
DVI plug #2- Selector ------> DVI_out-
DVI plug #3- \
DVI plug #4/ \_ Dual input monitor
/ with auto-select
VGA plug #1\ /
VGA plug #2- Selector ------> VGA_out-
VGA plug #3-
VGA plug #4/

The Gefen box above (or equiv solution), is the most
practical method to add VGA capability when the monitor is
stuck in digital land - but for $300 you could buy another
LCD monutor instead.

Paul