I want to purchase a Radeon HD 6850 but only have a 1.0 PCI-e slot on my mobo.
PCI-e is suppose to be backwards compatible and the difference in performance is negligible, BUT whereas 2.0 cards in 1.0 slot work fine - I've read where people have had issues using 2.1 cards in 1.0 PCI-e.
My question is this, do they make 6850's in 2.0 PCI-e?
All 6850s are PCI-E 2.1. Some of the older PCI-E 1.0 boards have compatibility problems with PCI-E 2.1, but most 1.0 boards will take a 2.1 card fine. Most of the time the problems are with the Socket 939 boards from AMD, and the really early LGA775 boards, the ones that tend to only support Pentium 4s and Pentium Ds. Check your board's manufacturer for a BIOS update, some of the boards that have this problem have had BIOS updates released to resolve this issue.
It is not a waste to run a 6850 with a dual core CPU. Most games do not have great multithreading support, and will run just fine on a fast dual core. Tom's Hardware did an article a while back testing an i3 530 with an HD 5850 (which is a bit faster than the 6850) and found no bottlenecking issues with the dual core CPU and a single 5850. You're only likely to hit a CPU bottleneck if you are playing at an extremely low resolution on a CPU intensive title, or you have a slow dual core, like a C2D 2.0 GHz.
they suggested I go with a better PSU or a 6850 (I chose the latter).
I'm thinking a 6850 would do fine with a 955 but I'm a novice and don't know if I'm missing something. The issue with the pci-e 2.0 vs 2.1 backwards compatibility came up in that thread, so I wanted to be sure before I ordered it to prevent running into any problems.
There should be no problems running a 2.1 card with that board and CPU. It has been receiving fairly regular BIOS updates up until 2010. If there was a PCI-E 2.1 problem, it probably would have been fixed in one of the newer BIOS revisions. You may have to use one of the newer revisions just to get the Phenom II X4 to work anyway. Edit: You need revision F15E at least for the new CPU to work. I'd say get the card, there is very little chance that you will have a problem.