Speed drops down by a half after a few seconds

[qweasd]

Hi,

When I run oclHashcat (plus or lite), the two AMD hc7900 GPUs run about at the same speed:

Ater 6s:

Code:

Session.Name...: oclHashcat-lite
Status.........: Running
Hash.Target....: ee98e55f3f62a11697889e502d237d3d
Hash.Type......: NTLM
Time.Started...: Thu Jul 11 12:47:39 2013 (6 secs)
Time.Estimated.: Thu Jul 11 12:50:21 2013 (2 mins, 30 secs)
Plain.Mask.....: ?1?2?2?2?2?2?2?3
Plain.Text.....: **lrz4m$
Plain.Length...: 8
Progress.......: 219414528000/5533380698112 (3.97%)
Speed.GPU.#1...: 17673.5M/s
Speed.GPU.#2...: 17671.4M/s
Speed.GPU.#*...: 35344.9M/s

But after some time, the speed of GPU #1 drops down by a half:

Ater 42s:

Code:

Session.Name...: oclHashcat-lite
Status.........: Aborted
Hash.Target....: ee98e55f3f62a11697889e502d237d3d
Hash.Type......: NTLM
Time.Started...: Thu Jul 11 12:47:39 2013 (42 secs)
Time.Estimated.: Thu Jul 11 12:51:08 2013 (2 mins, 40 secs)
Plain.Mask.....: ?1?2?2?2?2?2?2?3
Plain.Text.....: **585ih7
Plain.Length...: 8
Progress.......: 1415894794240/5533380698112 (25.59%)
Speed.GPU.#1...:  8239.9M/s
Speed.GPU.#2...: 17464.4M/s
Speed.GPU.#*...: 25704.3M/s

I tried playing with the --gpu-temp-retain, --gpu-accel, --gpu-loops switches, but no changes.

I am on 2008 R2 with 2x hd7900.

Any ideas?

Cheers

[atom]

Looks like your card hit 90c temperature. In this case GPU bios will clock down your card to 300 Mhz or less.