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Posted: Fri Dec 21, 2007 10:33 pm Post subject: VGA pin 9

I recently decided to fix up a very old PC that I had just lying around, but when I went to connect a monitor and it didn't fit, I found that there wasn't a hole for pin 9 in the VGA port. Is there an adapter out there to get around this?

Posted: Sat Dec 22, 2007 3:51 am Post subject:

Well, pin 9 isn't used for anything, so rather than spending money on an adapter you could just remove it.

Otherwise, for the less adventurous route, the answer you seek is here.

Posted: Sat Dec 22, 2007 1:34 pm Post subject:

Ouch, $8.50 shipping for a $7.95 part.

That pin is just used by newer (relative to the life of VGA, anyways) graphics cards to get the monitor's parameters, right? If I did remove the pin, would the monitor still work with computers that used that feature?

Guide Dog Joined: 08 Nov 2003 Posts: 8256 Location: MN

http://en.wikipedia.org/wiki/VGA_connector

Quote:
Pin 9 +5 V +5 V (DDC)

I don't know why a monitor would need a 5v power source... particularly not when it is plugged into the wall...

but if the pc is the old one, I say get the drill bit out and make a whole.

Posted: Sat Dec 22, 2007 4:36 pm Post subject:

It'd actually be a lot cheaper to just buy an extension cable from Newegg and rip the pin out.

http://www.newegg.com/Product/Product.aspx?Item=N82E16812119035

anglachel wrote:
http://en.wikipedia.org/wiki/VGA_connector

Quote:
Pin 9 +5 V +5 V (DDC)

I don't know why a monitor would need a 5v power source... particularly not when it is plugged into the wall...

but if the pc is the old one, I say get the drill bit out and make a whole.

I'm seriously tempted. Not like it'd be a big loss if I killed it; the computer is from the age when the only fan in the system was in the power supply.

Posted: Sat Dec 22, 2007 4:52 pm Post subject:

For the old VGA standard pin 9 was just a filler pin, no signal at all. For the newer revisions it is used to power the identification circuit in the monitor. The VESA standard states that the circuit should draw power from the monitor when it's turned on though, so that 5v is used when the monitor is off.

Quote:
Q: Why is +5 volts on pin 9 mandatory for system units and/or graphic cards?

A: It is becoming common for system management software to interrogate peripheral devices for product type and serial number as a form of asset management. This is usually scheduled for nighttime but if the monitor is powered off then no data can be collected. Providing +5 volts allows the DDC circuit in the monitor to remain active even when the monitor itself is powered off. Ref.: Section 4.1.4.1

Q: Is +5 volts mandatory for portable computers?

A: Portable computers that want to be able to claim compliance with VESA DDC standard version 2 must provide the +5 volt output. Ref.: Section 4.1.4.1

Q: Is +5V from the host required to be continuously active?

A: +5V should be provided whenever the host PC video port is active, or when the host PC is attempting to read the monitor's EDID data. In particular, mobile PCs running on battery power may disable the +5V output when the system video port is not active, to conserve battery power. Ref.: Section 4.2.

Q: What are the intended uses for the +5V output?

A: +5V is needed as a power source for the DDC and EDID circuits of a display monitor when the host is attempting to read the monitor's EDID data and the monitor's own local power supply is not yet turned on. This capability is especially important when a PC is initially booting up or when a mobile PC user enables the external video port, so that the PC can properly detect the type of display attached. This is the main use of +5V defined in the Enhanced DDC Standard. (The EDID and DDC circuits in a display monitor should always be powered from the monitor's own local power supply whenever it is available.) The E-DDC Standard does not directly define or constrain other possible uses for the +5V output, provided that the specified loading limits are not exceeded. For example, when the display monitor is powered on, +5V may be used as a logic signal to control display power states, i.e., signaling to the display whether or not the host PC video port is active, so that the monitor can decide when to go into a reduced power mode. This is the reason why the +5V must be provided continuously whenever the host PC video port is active. Since the host PC might be a mobile PC running on battery power, the total load on the +5V from the host PC must be limited to 1 mA maximum when the display has local power. Ref.: Section 4.2 & 4.4.

Posted: Sat Dec 22, 2007 5:04 pm Post subject:

Drilling a hole worked great! Smile

DSTG_II wrote:

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anglachel wrote:

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DSTG_II wrote: