According to the INQ, there will be no X1600 master cards as they are not needed. Just use 2- X1600's. Adds to the appeal and curiosity factor, although I can't see myself buying two cards when typically one higher end can do better for a lower price.
why would they need the bridge? SLI has proved you dont need the bridge and you can do hat internally through the bus.
A PCIe Bus is well more then enuogh for those two cards to talk to eachother.
The bridge and dongle are required to send the entire frame or scissored fram to the outputing card not just 'talk to each other'. The ATi's can send the frame to the compositing engine through the PCIe bus. Now there's alot of limitations using the PCIe bus at 8X + 8X, and one major consideration is resolution, which is likely why it's limited to the X1300 and X1600, because the X1800 would be playable at far higher resolutions and thus be pushing almost geometrically larger amounts of data very quickly saturating the PCIe bus.
I would not be surprised if this dongle-less Xfrie and SLi-less SLi are resolution restricted, and as we know for the X1xxx series that would have nothing to do with the outputting TMDS (dual link) and of course nothing to do with the receiving TMDS as it's not used to end the signal to the compositing engine.
Now this may not be the case but it wouldn't surprise me, since while normal play won't saturate the PCIe bus, having to communicate to the 2 cards AND then have one card send half every frame, or a whole alternate frame across the bus at the same time is likely to make things crowded. With the introduction of the dual 16x lane PEG slot MoBos this may change.
If you look closely at any of the early reviews that did not use the Xfire dongle or the SLi bridge, you'll see most of them talk about stuttering, and that was more frequent as IQ was boosted.
If anything I think that ATi over-estimated the need for the dongle on the X1600, and you might say it's useless, however it's better for them to plan for an Xfire card and then be able to say, nah just go out and grab another one , than vice vera and not be ready for the need for the Xfire card.
Considering the number of cack-ups in the graphics industry, caution and preparation aren't bad ideas.