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I stumbled upon a problem after I upgraded my hardware, I was so excited about it, but when I realized that I can't connect my monitors this disappointed me.

I have 3 FullHD 22 inch monitors with a resolution of 1920x1080 and all 3 with VGA ONLY inputs (yeah, I bought them more than 6 years ago), and a Sapphire Radeon 7970 with

  • 1 x DVI-I
  • 1 x DVI-D
  • 1 x Display Port
  • 1 x HDMI

ports (before that there was a simplier Radeon with 2 DVI-I's and a VGA port). As I saw on the hills of the internet there is no way to connect these monitors from a DVI-D, Display Port or HDMI to VGA with some Passive adapters? Or I can? I am not afraid of doing some DIY things to make it work, cause I don't really want now to try sell these monitors and find ones that come with normal modern inputs, because this is a lot of time and some higher expenses.

For now I am using only one monitor connected to DVI-I with an DVI-I to VGA adapter and it works fine, so remained other 2 to connect. What can be the solution for now?

  • Note that your video card (like most) only supports using two of the three non-DisplayPort outputs (DVI-I, DVI-D, or HDMI) at the same time. Your third monitor will have to be connected using an active DisplayPort to VGA adapter. – Ross Ridge May 4 '15 at 17:41
10

You are right: HDMI, DP and DVI-D use digital signals, while VGA uses analog signals. You'll need to buy adapters that convert those digital inputs to analog outputs (so yeah, no "passive" adapters).

VGA degrades quality quickly with bad/long cables as well as with high resolution displays (it'll need to send analog signals, changing the output voltage at around 200 MHz for FullHD, which is your resolution). Although you'll easily find cheap HDMI/DP to VGA adapters, they may not have such a good digital to analog converter (VGA outputs are usually attached to lower resolution displays, meaning 640x480 or 800x600 @ 60 Hz). I just mention this so you may consider start replacing your monitors at some point (maybe gradually, to avoid spending a lot of money). There are cheap FullHD monitors nowadays which I bet will provide better contrast/colors/fidelity than your VGA based monitors. If image quality/fidelity does not interest you, then go for the adapters, it will definitely be cheaper and they will let you extend your current monitors' life.

UPDATE

Of course VGA has evolved since its early days and nowadays supports higher resolution displays with good quality provided a good cable for signal transmission. However, VGA has still its limitations, and that's what I wanted to point out.

When trying to send analog RGB signals at 200 MHz in a 0.7 volts range where different voltage means different color, it is harder to achieve high fidelity/color-depth. Although that may not be a problem when talking about old monitors that only support VGA and which may not be able to represent pixels with higher fidelity anyway.

Having a monitor with both digital (i.e. DP or HDMI) and analog (VGA) inputs, this tests may help noticing some differences in color depth and black levels:

enter image description here

enter image description here

  • Would this solve my problem? amazon.co.uk/Cable-Matters-Active-Female-Adapter-Black/dp/… – Denees May 4 '15 at 13:17
  • @Denees: sure, you could use that one to connect one of your monitors to the HDMI output of your graphics card (I guess you already have the male-male VGA cable). – Peque May 4 '15 at 13:25
  • Cool, thx, now I have to find another one for Display Port too. – Denees May 4 '15 at 13:27
  • @Denees: wont be hard. ;-) – Peque May 4 '15 at 13:29
  • 2
    Regarding the loss of signal quality with long VGA cables, if that is an issue then you can put the adapter at the monitor end and use a long HDMI/DP/DVI-D cable. – Andrew Morton May 4 '15 at 13:42
4

There is simply no way to use a passive adapter as DVI-D/Display Port/HDMI are a complete other technology than VGA.

VGA uses analogue signals whereas DVI-D/Display Port/HDMI use digital signals.

DVI-I uses also analogue signals therefore you can have a passive adapter from DVI-I to VGA.

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