This new Revision of BFL chips w/ the metal layers seems to be able to hit higher Gh/s but still just as power hungry and hot!
@MrTeal, how was the board running w/ that Watercooling loop you had on it? Just wondering if it's worth picking up a decent closed loop system over a $30 120mm HS&Fan setup. It it lets me get an extra 5Gh/s while being able to use a 80-92mm Fan to cool off the vregs and others circuits then I'd probably go for it on atleast one of my boards.
Are the Sample chips you're using the new Revision chips by chance? Do you notice a big difference in what Coolers you're using since they output so much heat? And last question I promise, have you had any luck using a TIM as opposed to the heat pads? Hope the newer chips are more uniform as that'd make cooling much more effective.
So far I've only used the rev A chips on boards. When the production boards arrive I will be mounting one with some Rev B samples. Efficiency actually isn't terrible right now; while 130W for 30GH/s isn't great that's a little under the sweet spot for my 850W power supply. I'll probably pick up a proper gold or platinum PSU once I get a moment, it should perform better than the plain brown box HEC PSU I'm running them on right now.
The closed loop cooler seemed to work ok, but I've only tried it with decent (as opposed to great) thermal pads. I took it off when I took the videos because I didn't want to give the impression that you need to use water cooling.
Far more important than the cooler itself is the thermal interface between the two surfaces. While specs don't tell the whole story, the difference between a 0.25mm thermal adhesive tape like 3M's 8810 at 7.74°C*cm^2/W, versus the initial pads I was using (3.0°C*cm^2/W), vs something like the Fujipoly Ultra Extreme pads (0.4C*cm^2/W) absolutely dwarfs any differences between a good air cooler and a closed loop water cooler. I just really liked the water cooler since it moves the mass of cooler away from the board and makes probing test points easier.
I've actually had some good conversations with an applications engineer at Arctic Silver who has provided me some literature and samples on their products for my idea to bond a heatspreader to the ASICs so I can use a proper minimum bond line grease interface between heat spreader and cooler. Once the first production boards get built here in the next couple days I'll try that on the existing board I have to see what happens. The per chip temperature sensing is now being output out the debug UART (cg/bfgminer integration is still on the to-do list), so I'll be able to directly compare results between TIM+Hyper212 Evo, TIM+Water, and bonded heatspreader on the same board.
