GTX 680 mining does work but the performance is very disappointing at the moment. I think there may be some gains from drivers in the future though, since I'm only showing ~70% power usage. However, I highly doubt the GTX 680 will ever be competitive as a mining card.
Showing 123.40 Mhash/sec in Phoenix 2.0.0 with the following settings:
[cl:1:0]
kernel = opencl
name = GTX 680
disabled = False
worksize = 256
vectors = False
vectors4 = False
bfi_int = False
goffset = False
fastloop = True
aggression = 2
Vectors seem to reduce performance. Enabling goffset will cause the miner to error out and exit after about a minute. GPU clock was a constant 1241MHz for the test. (using +144 offset) Maximum load temperature was 67 C.
[04/06/2012 14:26:27] Welcome to Phoenix v2.0.0
[14:26:27] Connected to server
[14:26:27] Server gave new work; passing to WorkQueue
[14:26:27] New block (WorkQueue)
[14:26:27] Server gave new work; passing to WorkQueue
[14:26:31] [GTX 680] Result 00000000963d2b3a... ACCEPTED
[14:27:01] [GTX 680] Result 00000000a91cf2e1... ACCEPTED
[14:27:02] Server gave new work; passing to WorkQueue
[14:27:04] [GTX 680] Result 00000000dca6829f... ACCEPTED
[14:27:12] [GTX 680] Result 00000000747b6cd5... ACCEPTED
[14:27:15] [GTX 680] Result 000000005d990449... ACCEPTED
[14:27:27] Server gave new work; passing to WorkQueue
[14:27:32] [GTX 680] Result 0000000021cd0601... ACCEPTED
[14:28:02] Server gave new work; passing to WorkQueue
[14:28:27] Server gave new work; passing to WorkQueue
[14:28:28] [GTX 680] Result 00000000db036548... ACCEPTED
[14:28:51] Server gave new work; passing to WorkQueue
[14:28:51] New block (WorkQueue)
[14:28:52] Server gave new work; passing to WorkQueue
[14:29:03] [GTX 680] Result 0000000057bdfa90... ACCEPTED
[14:29:26] Server gave new work; passing to WorkQueue
[14:29:52] Server gave new work; passing to WorkQueue
[14:30:04] [GTX 680] Result 0000000093be9bbe... ACCEPTED
[123.40 Mhash/s] [9 Accepted] [0 Rejected] [MMP]