Didn't mean to go OT so much, but since the OP hasn't responded back yet, what the heck. I'm a bit surprised the 4890 is so far only showing about equal performance to the GTX 285 and at a speculated similar price range. Of course those are just synthetic benches and theoretical prices so far though, unless there's some new info out there I've missed.
It was a bit off topic and the thread should have been in the troubleshooting section. I'll allow it and rather spend some time troubleshooting with him when he responds. :)
I don't think the 4890 is nothing more then a R700 series chip. Much like the GTX275 being GT200. They are simply OC variants of the same series.
GTX295 is also rumored to come on a single PCB design.
I think that Nvidia and ATI needs to sell out some chips before we see the new designs like R800 and GT300. Should be fun, since they both have a new architecture from what I have read, and, both supports the same DX version ensuring faster adoption to it.