How and which part of PC decide which display output to use(vga,hdmi,dvi) ?

For now I will assume the graphics card decides which output to use.

How it does this is unknown to me. Does anybody have some references/documentation ?

I am particularly interested in nvidia's GT 520.

I believe this device works as follows:

1. If an HDMI cable is connected it will try to use it.

However this procedure overlooks the possibility that HDMI is only used for AUDIO connection and thus this procedure is flawed.

2. If an HDMI cable is connected by the HDMI device is off it might assume the monitor is off or it will probably use the DVI output.

3. Only if HDMI cable is disconnected and possibility DVI cables will it fall-back to VGA output.

So basically as far as I know it's impossible to instruct the GT 520 to always use the VGA output ?!?

It seems this graphics card has some "auto-detect" logic which in my case is flawed and does not do what I want.

I want it to always use VGA, but do enable HDMI audio.

It is possible to boot as follows though, a re-boot is required, pulling out the hdmi cable will not fall back to VGA.

Boot process:

1. Attach VGA cable only.
2. After boot is complete attach HDMI cable, make sure HDMI device is off.

This is ofcourse a bit risky to do this every time.

The BIOS has no option to select which display output to use.

To me it's clear this is a short coming in the design of these electronics.

I do not know if newer hardware/bioses/uefis and such have selection/guis to configure which output to use.

In case HDMI was auto-selected then using an HDMI monitor or HDMI-to-vga cable does offer some possibilities of getting GUI back on monitor though it looks very weird... scan line issues.

But it's clear enough to re-boot the computer and pull out the hdmi cable and re-attach vga-cable to system.

It's clear to me that this setup of using GT 520 for VGA and HDMI audio is not a viable solution and only viable for experimenting with nvidia's audio driver, which I suspect might have an audio-channel swapping issue with SL/SUB or it's my receiver, maybe later though.

Quite a weird experience this auto-display-selection tech failing.

If you like weird electronics behaviour this one tops many others =D and I highly recommend you try it out to get that x-files feeling ! =D

Bye for now,
Skybuck.

Damn, I forgot to test out DVI-FULL to VGA + HDMI AUDIO.

I forgot I have these DVI-TO-VGA cables and I forgot the GT 520 has DVI-FULL.

I should have tried that out... but the main problem was the NVIDIA drivers failed to install properly.

Could also be a windows 7 issue, perhaps same as with creative drivers.

Hope not.

So I pulled out the GT 520 and replaced it with GT 1030.

I will now download latest GT 1030 driver and try to install that.

Kinda suxxx... how the older nvidia driver failed to install... this kinda ruined my audio experiments...

I might have thought of the DVI option or maybe not.

But at least now I write this note to myself to perhaps try this experiment in the future.

For now I have no idea what would happen if the following situation occurs:


1. VGA monitor connected to GT 520 via DVI-to-VGA cable.
2. Receiver connected to GT 520 via HDMI cable for audio only.

Which devices would the GT 520 prefer ?

The fake-DVI or the somewhat-fake-Receiver (since it's only hdmi-audio) ?!?

Though graphics card doesn't know it's only half a receiver lol.. doesn't even know it's a receiver, graphics card thinks it's a monitor =D

Perhaps some day in the future when I do a fresh install of windows 7 or maybe XP I will re-try this experiment.

For now I am not doing it cause I have no idea how to get the drivers working again.

After reboot the driver complaints that some Wizard is already running.

Perhaps it's adobe reader service/startup crap/check that causes it... so I have disabled that for now.

Bye for now,
Skybuck.

wrote:
Damn, I forgot to test out DVI-FULL to VGA + HDMI AUDIO.

I forgot I have these DVI-TO-VGA cables and I forgot the GT 520 has DVI-FULL.

I should have tried that out... but the main problem was the NVIDIA drivers failed to install properly.

Could also be a windows 7 issue, perhaps same as with creative drivers.

Hope not.

So I pulled out the GT 520 and replaced it with GT 1030.

I will now download latest GT 1030 driver and try to install that.

Kinda suxxx... how the older nvidia driver failed to install... this kinda ruined my audio experiments...

I might have thought of the DVI option or maybe not.

But at least now I write this note to myself to perhaps try this experiment in the future.

For now I have no idea what would happen if the following situation occurs:


1. VGA monitor connected to GT 520 via DVI-to-VGA cable.
2. Receiver connected to GT 520 via HDMI cable for audio only.

Which devices would the GT 520 prefer ?

The fake-DVI or the somewhat-fake-Receiver (since it's only hdmi-audio) ?!?

Though graphics card doesn't know it's only half a receiver lol.. doesn't even know it's a receiver, graphics card thinks it's a monitor =D

Perhaps some day in the future when I do a fresh install of windows 7 or maybe XP I will re-try this experiment.

For now I am not doing it cause I have no idea how to get the drivers working again.

After reboot the driver complaints that some Wizard is already running.

Perhaps it's adobe reader service/startup crap/check that causes it... so I have disabled that for now.

Bye for now,
Skybuck.

Regarding video card automatic detection of cables...

I've had similar problems, in that the detection is faulty.

I had been using a DisplayPort to VGA adapter. Most of the
time, this works properly. But coming out of sleep, the screen
would be black.

Some experiments revealed, that coming out of sleep, the
single HDMI port on my video card was active, even though
no HDMI cable was plugged in. The video card is not supposed
to drive unpopulated ports!

This means, in a limited sense, that "HDMI takes priority"
for some strange reason. And it's only an issue with Sleep.

I now own a DisplayPort to VGA and an HDMI to VGA adapter.

I have since chosen to preferentially use the HDMI to VGA
adapter, and now there are no more problems with entering
and exiting the Sleep state. The video card "quirk" cannot
disturb my setup. But if I were to actually use the
DisplayPort, and Sleep the machine, I bet there will be
more surprises in multi-monitor mode.

My card has only four outputs. HDMI + 3 * DisplayPort.
So I don't have a lot of choices for I/O. If I had
two HDMI and two DisplayPort, that would kinda be
a better mix. But the three DisplayPort are that
way, for the "panorama" mode, of putting
three 1920x1080 monitors side by side for gaming
and having a unified 5760x1080 gaming surface.
That's why the connectors were set up like that.

The very best video cards come with six connectors
on the faceplate, and for space reasons, some of
those will be mini-DisplayPort ones.

Paul