I have the SAME CARD and the SAME PROBLEM. Just got it off 'imagestore' via eBay. I too removed my heatsink, the chip said 5600 Ultra and has a heat spreader (version 2 flipchip, the 'good' one, ha!)
Firstly all the files you could ever want are here ;
See if this sounds familiar;
(1) Bios is 188.8.131.52.0 which is NON Ultra
(2) Bios we NEED is 184.108.40.206.00 (FX5600 Ultra) (see url above)
(3) NVFlash says 'Board ID Mismatch' or 'GPU Mismatch' depending on whether you suppress warnings or not and fails
(4) Core is 270 (2d) and 300 (3d) instead of 400
(5) Memory is 400 instead of 800 (think 400 is right but not treated as ddr?)
(6) Coolbits won't accept any other speeds EVEN UNDERCLOCKING
(7) Powerstrip allows 448 core and 443 memory max so far
(8) It runs 33% slower than my ti 4200
(9) We got ripped off, the thing is a total lemon
I'm determined to get this damned ultra bios to work on it, and very carefully clock it to death. What a joke, I'm ordering a gpu waterblock for this and now I discover it's probably a waste of time.
Very frustrated, it's 3:48am and I'm still trying to find the answer, we should be able to sue. You can't f**king use words like 'Ultra' and clock it over 33% SLOWER than a 'proper' ultra dammit. Will be requesting an exchange on something else even though I don't think it's the shop's fault, but on the other hand this isn't fit to sell, it's junk.
Wellington, New Zealand.