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.