X8x cards in CF can run over 1600x1200?! 1920x1200!!!

[dug777]

http://www.legitreviews.com/article/474/10/

Interesting

 

[BFG10K]

Repost.

 

[lavaheadache]

Not really a repost considering you have to have read that previous thread which was of a different topic. He could have searched and never come up with anything. I think it warrants a new thread, although I managed to see this in the other thread this morning.

 

[Munky]

Someone should give the memo to Rollo....

 

[Gstanfor]

I believe Dug is trying to say that R4xx is limited to 1600x1200 when used in crossfire configurations, yet the legithardware review is providing R4xx crossfire results @ 1920x1440 ...... a fascinating scenario indeed!

 

[dug777]

Originally posted by: BFG10K
Repost.

Oh noes, not a barely connected repo-xy!

As has been said, there's more than enough justification for a thread in it's own right.

 

[Paratus]

So did legit screw up or are we seeing some driver magic?

 

[Matt2]

Originally posted by: munky
Someone should give the memo to Rollo....

I dunno. This was documented by quite a few sources besides Rollo.

I am skeptical of this. Does it matter anyways?

X8xx CF is useless anyways.

 

[Matt2]

As you probably know, the required pass-band in megahertz is calculated by the formula R = (1.4*X*Y*V)/1000000 where 1.4 is a device lag compensation coefficient, X and Y are the horizontal and vertical resolutions, and V is the vertical sync frequency. You can solve this simple equation to see that a bandwidth of 165MHz is only sufficient to output a 1600x1200 picture at 60Hz frequency. A 75Hz refresh rate would require a bandwidth of over 200MHz; and an 85Hz refresh rate would require a bandwidth of about 230MHz. It turns out that CrossFire cannot do what all multi-GPU technologies are expected to do, i.e. to work in high resolutions! Yes, 1600x1200 is formally supported, but it is absolutely unacceptable to have a refresh rate of 60Hz. Talking about higher resolutions, for example 1920x1080, a bandwidth of 175Hz is required even for a 60Hz refresh rate. So, people who have a HDTV 1080i display device or a big CRT monitor may feel disappointed.

link

 

[Keysplayr]

Yeah, it wasn't a resolution limitation IIRC. It was the refresh rate problem. 60Hz at anything 1600x1200 or higher. Which suxorz.

 

[dug777]

Originally posted by: keysplayr2003
Yeah, it wasn't a resolution limitation IIRC. It was the refresh rate problem. 60Hz at anything 1600x1200 or higher. Which suxorz.

surely for LCD that wouldn't be an issue? They're usually '60Hz' anyway aren't they?

 

[bunnyfubbles]

Who has a 24" LCD for me to confirm this with?

I actually do have two older X800 cards, one being a master xfire card that I got for super cheap a while back for an older computer...

 

[lavaheadache]

Originally posted by: bunnyfubbles
Who has a 24" LCD for me to confirm this with?

I actually do have two older X800 cards, one being a master xfire card that I got for super cheap a while back for an older computer...

I got a 24, let me mail it to you for testing Then once it works everybody can go run out and buy an X800 crossfire setup, j/k. Serious though, This great news for people who want a cheap upgrade and dont need to play with the latest features.

 

[PingSpike]

The 60Hz thing sounds stupid yes, but most LCDs only do that anyway.