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Why did they not share the HDMI port with the DP
http://www.wsgf.org/phpBB3/viewtopic.php?f=66&t=18504		 Page 2 of 4
Author:  bowenac [ 01 Dec 2009, 17:05 ]
Post subject:  Why did they not share the HDMI port with the DP
So would this not be possible if they just went with HDMI instead. Why not just make it with 2 DVI and 1 HDMI with none of them shared. How can this be possible with DP but not with HDMI. I guess I just don't understand why they didn't just use 2 DVI and 1 HDMI. Or 3 HDMI ports. And get rid of the DP all together. Just about every monitor has a HDMI port now. And if they don't a HDMI to DVI adapter they are about $5.
Author:  Greg Ellis [ 01 Dec 2009, 17:24 ]
Post subject:  Why did they not share the HDMI port with the DP
So would this not be possible if they just went with HDMI instead. Why not just make it with 2 DVI and 1 HDMI with none of them shared. How can this be possible with DP but not with HDMI. I guess I just don't understand why they didn't just use 2 DVI and 1 HDMI. Or 3 HDMI ports. And get rid of the DP all together. Just about every monitor has a HDMI port now. And if they don't a HDMI to DVI adapter they are about $5.


It's not just about connector choices, there's a limitation in the hw design. The 5000 products support a maximum of 2 legacy outputs. Legacy being DVI, HDMI, VGA, Component, whatever you like. So you can run DVI + DVI, or DVI + HDMI, or HDMI + HDMI, or VGA + DVI - any combination of two.

Most prior products are exactly the same - they support a max of two legacy outs.

On top of those two legacy outs, the 5xxx boards add DP ports. You can have as many DP ports as you like, up to the max outs supported by the chip (max is 6, for 58xx, I believe).

If you want to use one of those DP outs to drive a legacy monitor, you need an active dongle - i.e. a piece of h/w that interfaces with the graphics board as if it were a DP monitor, and then actively translates the DP content to drive a legacy display, generating all of the required clocks and signals, etc.

It doesn't have to be a $100 active dongle. It could be a $30 DP to VGA. Or some other design. But it does need to be active, because the board can only support two legacy displays, not three or five or eleven. Everything beyond those two is DP only.
Author:  bowenac [ 01 Dec 2009, 17:28 ]
Post subject:  Why did they not share the HDMI port with the DP
Ok thanks for clearing that up. That was a good explanation. It doesn't matter I already ordered the adapter anyway haha. Was just wondering why this and why that.
Author:  BHawthorne [ 01 Dec 2009, 17:47 ]
Post subject:  Why did they not share the HDMI port with the DP
It's a design limitation of how the electronics that regulate the signal timing works. DP has no such clock limitions by design, but with DVI and HDMI and whatever else that is labeled "legacy", each port needs it's own dedicated clock hardware. DP, on the other hand, has a single new design of clock that is shared by all the DP ports on the card by design. It's a major archetecture change, hence the label of "legacy" for the older port designs. "Legacy" ports require dedicated clocks, one per port, while DP shares a single clock for all it's ports.
Author:  Gilly [ 01 Dec 2009, 22:21 ]
Post subject:  Re: Why did they not share the HDMI port with the DP
I suppose a more elegant solution would of been if ATi gave each card an option of an adaptor bundles with the card. Although, as I type this, something seems to stick in my head that there might be something like this planned.
Author:  Dave Baumann [ 01 Dec 2009, 23:25 ]
Post subject:  Re:
But they decided to go with tried and tested 2x DVI with 2 other ports, one of which is becoming more common, the other is just in its infancy with PC teritory.

The point it was to offer the same level of support as the previous generations (via DVI) and extend the capbilities with DP. For many of the users that have 2 panels then they can take the extension just by buying a new DP panel; that may not be many from here though as quite a few from this particular site are moving from 3 DVI to Eyefinity.
Author:  Dave Baumann [ 01 Dec 2009, 23:33 ]
Post subject:  Re:
"Legacy" ports require dedicated clocks, one per port, while DP shares a single clock for all it's ports.

I'd posit that the term "legacy" stems from what interfaces have active development paths; of the many display outputs found on a graphics adapter only two have active development communities and roadmaps going forward - DP and HDMI.

DP takes off from where DVI left off with VESA, and is a license free interface developed specifically for the PC community. HDMI is developed off one of the legacy standards, has royalties associated with it and is being primarily developed for the CE community and as such may add featured that make little sense for PC's.
Author:  Gilly [ 02 Dec 2009, 00:07 ]
Post subject:  Re: Re:

The point it was to offer the same level of support as the previous generations (via DVI) and extend the capbilities with DP. For many of the users that have 2 panels then they can take the extension just by buying a new DP panel; that may not be many from here though as quite a few from this particular site are moving from 3 DVI to Eyefinity.


I worded it very badly, what I meant was something along the lines of:

2x DVI because it works and most people will have DVI screens, HDMI for HT applications, and DP for future proofing.

My personal use for eyefinity would be somewhere along the lines of what was possible before, so I wouldn't care for 3 monitor span, maybe 1 huge screen for gaming and then another for Firefox, Foobar etc etc, so for me, what the design constraints are do not matter for me one bit. I will buy what I want, and it will work :P
Author:  SunSp*t [ 02 Dec 2009, 10:44 ]
Post subject:  Re:
Yea thats what I figured but in that case why not just go all HDMI. The HDMI port looks to be about the same size as Display Port. Why even add the Display Port at all.


The answer isn't as simple as it might appear. BTW I haven't read the entire thread so this may all be addressed by others. I just don't have the time to read every post, so please forgive any duplication of answers...

The whole DVI-HDMI similarity is one thing (I see BH and others understand that).

The other (and I thought I mentioned this somewhere earlier...) thing is that HDMI has some serious issues which makes it much less desirable than DP:

[list]HDMI's resolution is essentially capped at 1920H 1080V 60Hz.
Each HDMI output carries a licensing fee.
We could spec a mini-DP connector, but not a mini HDMI coonector.
HDMI acceptance at EF inception was very, very poor, even in consumer TV.
HDMI cables have been pretty expensive.
HDMI cables are thicker, less flexible than DP's.
HDMI requires independent clocks, which raises the silicon cost noticeably.
HDMI's max cable length is less than DP's.
DP was designed for built-in scaling, something HDMI was not built for.
I probably forgot a few.[/list:u]

It was pretty straightforward HDMI was not going ot be the interface of choice three years ago. Would I have made a different decision knowing what I know now? No. DP is still the best choice for all of us.
Author:  SunSp*t [ 02 Dec 2009, 10:47 ]
Post subject:  Re: Re:
DP takes off from where DVI left off with VESA, and is a license free interface developed specifically for the PC community. HDMI is developed off one of the legacy standards, has royalties associated with it and is being primarily developed for the CE community and as such may add featured that make little sense for PC's.



And I see DaveB has addressed much of the same stuff (like I said I don't have the time to read all these threads...).
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