Serious CrossFire limitations

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16-09-2005, 10:00 AM
NikolaX

Serious CrossFire limitations

Quote:

As many are aware by now, ATI’s Crossfire technology uses an external link to connect the Master and Slave cards together (it's sort of like a 3-headed dongle with DVI connectors at the ends). What’s not generally known is that the backbone for this setup is a Silicon Image SiL 1161 chip which is installed on the X8-series Master cards. The SiL 1161 is there to receive output passed over the external link from the Slave card in the Crossfire setup and pass it on to the Master card.

Sounds decent on paper and everything, but if you check out the specs for the 1161 on this page you will see that it is limited to single-link TMDS @ 165MHz. This means that the max 3D resolution for any X8-series Crossfire setup is 1600x1200 @ 60Hz. That means no high-res Crossfire gaming beyond 1600x1200, no 1600x1200 at a flicker free refresh rate, and no widescreen 1920x1200.

The word 'Oops' springs to mind, and that's putting it mildly. You can find the story here.
16-09-2005, 10:38 AM
Butcher

With high-end gamers favouring big widescreen TFTs these days, that's a bit of a limitation. Likely to lose them some sales to nvidia (which afaik doesn't have such a restriction).
16-09-2005, 11:04 AM
Starburn

Well.. doesn't bother me.. I've never seen the need to go beyond 1024x768 on a CRT and with my current TFT 1280x1024 looks great :)
16-09-2005, 11:20 AM
YorkieBen

how many people use a tft with a resolution over 1600x1200? plus 60hz is fine for tfts.
16-09-2005, 11:26 AM
crepness

This could all be a bit of BS. We won't know anything for definite until Crossfire actually comes out tho I can't see ATI shooting themselves in the foot like that.
16-09-2005, 01:09 PM
Kumagoro

I second yorkie doesnt matter for TFT's
16-09-2005, 03:15 PM
charger

aye yorkie is right on tft's not many people fork out near a grand for a huge ass tft monitor.. :shocked2:
16-09-2005, 03:27 PM
BUFF

Quote:

Originally Posted by YorkieBen

how many people use a tft with a resolution over 1600x1200? plus 60hz is fine for tfts.

but I play using 1600x1200@85Hz all the time on my 19" & 21" CRTs - I've even been known to go up to 2048x. It's a real concern - 60Hz just isn't good enough.
16-09-2005, 03:30 PM
nev_payne

So they're relying on a 3rd party for the cross-fire bit of the cards? Ouch - bad play ATi. Nvidia get my count.
16-09-2005, 03:41 PM
kalniel

60hz is perfect for TFTs, but yes, low for CRT.

Is that 60hz per card, thus with AFR going to 120hz overall?

I also don't get how a 165hz bandwith equates to 60hz at 1600x? (Given it says 165hz at UXGA)
16-09-2005, 08:32 PM
Chemical_Ali

crossfire will support 1920x1200@52hz

http://www.theinquirer.net/?article=26228
16-09-2005, 09:10 PM
oralpain

I probably won't move to an LCD for gaming for quite a while. 1600x1200x60Hz is plainly not enough for my CRT.

Quote:

Originally Posted by nev_payne

So they're relying on a 3rd party for the cross-fire bit of the cards? Ouch - bad play ATi. Nvidia get my count.

NVIDIA cards use the same 3rd party (silicon image) for decent anolog display quality.

All video card makers rely on a 3rd party for pritty much every thing that is not the GPU/board. In many cases even those are made by third parties.

Quote:

Is that 60hz per card, thus with AFR going to 120hz overall?

I also don't get how a 165hz bandwith equates to 60hz at 1600x? (Given it says 165hz at UXGA)

It's 60Hz.

The TMDS runs at 165MHz, not Hz. 1600x1200x60Hz at 32-bit color is the very best you are going to get out of 165Mhz.

It's kinda like a RAMDAC. Most cards have a (or a pair of) 400MHz RAMDAC. This is good enough for 2048x1536@85Hz, 32-bit color.