What am I missing?

[pragmatic]

So I'm running some bruteforce attacks with a system using 8 x 7970s and I can't seem to get my utilization up to full speed.

For instance:

$ ./oclHashcat-plus64.bin -a 3 -m 1000 -n 160 --gpu-loops=1024 --remove tobecracked ?a?a?a?a?a?a?a?a
oclHashcat-plus v0.09 by atom starting...

Hashes: 4 total, 1 unique salts, 4 unique digests
Bitmaps: 8 bits, 256 entries, 0x000000ff mask, 1024 bytes
Workload: 1024 loops, 160 accel
Watchdog: Temperature abort trigger set to 90c
Watchdog: Temperature retain trigger set to 80c
Device #1: Tahiti, 2928MB, 1000Mhz, 32MCU
Device #2: Tahiti, 2933MB, 1000Mhz, 32MCU
Device #3: Tahiti, 2933MB, 1000Mhz, 32MCU
Device #4: Tahiti, 2933MB, 1000Mhz, 32MCU
Device #5: Tahiti, 2933MB, 1000Mhz, 32MCU
Device #6: Tahiti, 2933MB, 1000Mhz, 32MCU
Device #7: Tahiti, 2933MB, 1000Mhz, 32MCU
Device #8: Tahiti, 2933MB, 1000Mhz, 32MCU
Device #1: Kernel ./kernels/4098/m1000_a3.Tahiti_1016.4_(VM).kernel (348640 bytes)
Device #2: Kernel ./kernels/4098/m1000_a3.Tahiti_1016.4_(VM).kernel (348640 bytes)
Device #3: Kernel ./kernels/4098/m1000_a3.Tahiti_1016.4_(VM).kernel (348640 bytes)
Device #4: Kernel ./kernels/4098/m1000_a3.Tahiti_1016.4_(VM).kernel (348640 bytes)
Device #5: Kernel ./kernels/4098/m1000_a3.Tahiti_1016.4_(VM).kernel (348640 bytes)
Device #6: Kernel ./kernels/4098/m1000_a3.Tahiti_1016.4_(VM).kernel (348640 bytes)
Device #7: Kernel ./kernels/4098/m1000_a3.Tahiti_1016.4_(VM).kernel (348640 bytes)
Device #8: Kernel ./kernels/4098/m1000_a3.Tahiti_1016.4_(VM).kernel (348640 bytes)

[s]tatus [p]ause [r]esume [b]ypass [q]uit => s
Status.......: Running
Input.Mode...: Mask (?a?a?a?a?a?a?a?a)
Hash.Target..: File (tobecracked)
Hash.Type....: NTLM
Time.Running.: 55 secs
Time.Left....: 1 day, 8 hours
Time.Util....: 55394.6ms/355.5ms Real/CPU, 0.6% idle
Speed........: 57243.4M c/s Real, 58087.3M c/s GPU
Recovered....: 0/4 Digests, 0/1 Salts
Progress.....: 3170975088640/6634204312890625 (0.05%)
Rejected.....: 0/3170975088640 (0.00%)
HWMon.GPU.#1.: 77% Util, 66c Temp, 31% Fan
HWMon.GPU.#2.: 77% Util, 64c Temp, 30% Fan
HWMon.GPU.#3.: 77% Util, 67c Temp, 33% Fan
HWMon.GPU.#4.: 77% Util, 64c Temp, 30% Fan
HWMon.GPU.#5.: 77% Util, 64c Temp, 30% Fan
HWMon.GPU.#6.: 77% Util, 65c Temp, 30% Fan
HWMon.GPU.#7.: 77% Util, 59c Temp, 24% Fan
HWMon.GPU.#8.: 77% Util, 65c Temp, 30% Fan

Using -lite gets them all going 99% just fine, but for plus it seems to ceiling out around 77-82%.

Any thoughts/suggestions?