How overclockable are the boards that are being shipped now? Is the power regulator still the limiting factor? Has anyone tried to replace it with one that can handle more power?
It's power reg + heat removal. My regulator was overheating like crazy at 41GH/s. The board would mine for a few mins but the regulator would turn off and I had to reset it everytime. I think the board was drawing around 70W power. I think with adequate cooling of chips + regulator, these boards can reach 40 - 42GH/s.
this. my regulator *seemed* to be staying on, but chips would drop like flies and the board often needed a reset. with heatsinks on the back of the regulator though, im now able to handle 40+/-1 GHash
as for heatsinks, i would advise against the massive slab mentioned a few posts up. at 12mm thick, you almost certainly will not be able to put a card in every slot, and the weight of such a big slab may mess up the cards unless they're braced. Look for something in the 6-8mm thickness - I found some terrific heatsinks that were 35x35x6mm and each one perfectly covers 4 chips (4 heatsinks per board + mini heatsinks for regulator). These do a great job pulling away the heat and there is space to fill the slot behind
ps: my order 13X h-board shipped today, and expected delivery is friday 5pm - fingers crossed for a weekend of hashing