It is an ISP header. I pulled firmware off the first one to come in the shop back in Batch 1, but since it was a customer machine I wasn't authorized to do anything that would void the warranty. Only enough to get the chip number and a firmware dump. I haven't seen what it'd take to modify my S7 firmware for an S9 but it's probably not difficult, I just don't have one to test it on.
Tell ya what, I'll be getting 2 more when Bitmain has more s9's for sale so how about I have one drop shipped to ya to tinker with?
One thing I'd like to be able to tweak is the starting voltage. On my batch-1 and one batch-3 it usually takes a couple reboots to get all the cards firing on all cylinders. On the b1 it is card-3 (the usually hot one) but oddly enough on the b3 it is the middle card that needs a few restarts to get up to speed.