Active DP-to-DVI adapters ?

[Phrik]

What's the difference in the 100$ active DisplayPort-to-DVI adapters and a $15 normal DisplayPort-to-DVI adapter ?

Researching at the moment, but any shared info from this forum is much appreciated

 

[kllrnohj]

DisplayPort and DVI have two different signals. Active adapters transcode one signal into the other. Passive adapters (the $15 ones) don't. DisplayPort has pins on it that allow it to carry a DVI signal as well as the DisplayPort signal (just like DVI had separate pins for VGA signals). Passive adapters use that legacy signal and provide the appropriate physical interface. If that legacy signal isn't present, then they don't do anything. Hence why the cheap $15 ones don't work for Eyefinity, because the card can only output 2 DVI signals. Thus when 2 DVI outputs are in use (be it DVI or HDMI), the DVI signal that would normally be connected on the DP output is no longer functional.

 

[J Macker]

I tried the passive adapter from Monoprice that many have said works fine. It does NOT work properly. The screen flickers frequently. Gives me an idea of what it would be like to have epilepsy.

Purchase the Accell adapter and it will work perfect.

 

[inotocracy]

I tried the passive adapter from Monoprice that many have said works fine. It does NOT work properly. The screen flickers frequently. Gives me an idea of what it would be like to have epilepsy.

Purchase the Accell adapter and it will work perfect.

Eh? Everyone says that passive ones don't work. Unless you're referring to the passive DP->VGA?

 

[J Macker]

Yeah, I was talking about the DP-vga. Sorry for the confusion.

 

[Kritter]

Its not about transcoding, its about dp having lower voltage levels than dvi/hdmi.

 

[don_xvi]

Funny, let's go for a 3rd version on the difference...
I believe it's that DP doesn't need a RAMDAC (I guess that function is in the monitor?) and the ATi cards only have 2 RAMDACs. The active adapter does whatever a RAMDAC does.

As referenced above, there are also passive DP-VGA adapters and those can be used to generate an analog signal, but seem to be plagued by some performance issues.

 

[ChristopherB]

But what I don't understand is that it has already been shown that a single link DVI output works fine via a passive DP to DVI connection (dazboots had it working).
The diagrams shows that there are 6 tmds units. A dual link dvi output would need two but single link dvi output, hdmi and DP only need one. If the DP output on the current 5870 card has shown to be fully capable of driving a SL DVI output via a passive connection then why can't the remaining tmds units, i.e. all six outputs of the Eyefinity6 card do the same? If it is capable of driving 6 x 2560x1600 dp outputs via a single tmds each then why can't it drive 6 x 1920x1200 HDMI/DVI outputs that also only require a single tmds each and thus don't require active adaptors?

While there are Six TMDS/DP transmitters, there are only 2 clock sources on the ASIC. The issue with legacy display is that they all need their own clock generator - as soon as you plug in two DVI/VGA/HDMI you run out of clock sources. DP can time multiple outputs from a single clock generator.

What we do with these boards is add an additional clock source externally from the ASIC that is good for driving DP timing, but unfotunatly not others (the clock source is actually shared for another use, so we can't just arbitarily have any timing).

If you plug in a passive adapter to the DVI+DVI+HDMI+DP design then you it will use an internal clock source, up until you start plugging in other panels.

What if someone wanted to drive 6 DVI/HDMI panels from the card, 6 active adaptors? Each with their own power supply???

As already posted, 2 can be passive in this scenario.

Here is your answer courtesy of the HD5800 series product line manager, Dave Baumann