Things did not go so well when I booted up - my first GPU was not making contact apparently and soared to 110C
idle, shutting off completely within about 15 seconds. I may have busted this card while troubleshooting.
The second wasn't making
good contact, but was holding around 60C idle.
By comparison, my Phenom II 1090T was
28C idle for the short time I got to monitor it.
I highly recommend against the Koolance full-coverage blocks, at least for my combination.
While there is no full-coverage block for non-reference 6950s, the PCB design for reference 6870s is exactly the same as the XFX 6950s I've got, short one mounting hole. All the VRM, ram, etc are in exactly the right spots.
The Koolance 6870 blocks I got are
crap, however, as far as I can tell. The mounting spacers don't line up properly with all the holes; 5 out of 9 mounts line up perfectly, the others are off by only a millimeter or so, but just enough prevent proper mounting.
On the stock heatsink the 4 mounting spacers around the GPU are flush with the top of the PCB (chip side), and XFX uses screws with springs that 'push through' to keep pressure on the GPU plate. The Koolance block, on the other hand, has spacers that are flush with the *bottom* of the PCB, so the springed screws I have apply no pressure at all, hence the temperature fail. Koolance does not supply any screws for these 4 mounting holes, even though they're the most important.
I had to drain my loop and re-do both GPU blocks, adding some washers to get better pressure between the GPU and the cooling plate, and I'm now leak testing again. Hopefully it goes better this time around.
Unfortunately it was pretty difficult to find reviews for any of the 6870 waterblocks so comparison was hard when I picked them up; I went with the slightly more expensive Koolance blocks versus the 'cheap' WaterCooling blocks, figuring a more well-known brand and higher price would indicate better quality. Lesson learned.
[edit] While I was at it, I also replaced that awful tube between the GPU blocks and the reservoir - I had made it longer with the intention of being able to move the reservoir in and out of the case for filling, since it's mounted at the top. Turns out this was applying uneven pressure at the GPU fitting, and it was starting to slip pretty badly. I shortened it up almost 2" (!!) and it's
much better now, and I can still move the reservoir easily. I'm learning
lots of lessons from this endeavor