Very slow WPA cracking on NVIDIA 8500 GT Windows

Hi.

I'm testing oclHashcat 1.01 on Windows running with NVIDIA GeForce 8500 GT, 256MB, 918Mhz, 2MCU, PC: Windows 7 64bit , Intel Core I5-2400 3.10GHZ (4 Cores)

When testing MD5 hashes, I get around 37000 khs which is reasonable and it seems to work smoothly.
But when attempting to run WPA/WPA2 cracking, it seems to be very very unreasonably slow, around 600 H/S, here is my command line and output, any idea ?!?!?, I also tried different --gpu-accel and --gpu-loops but getting the same results for WPA cracking.


C:\>cudaHashcat64 -m 2500 -a3 eapol.hccap ?l?l?l?l?l?l?l?l?l

cudaHashcat v1.01 starting...

Hashes: 1 total, 1 unique salts, 1 unique digests
Bitmaps: 8 bits, 256 entries, 0x000000ff mask, 1024 bytes
Applicable Optimizers:
* Zero-Byte
* Single-Hash
* Single-Salt
* Brute-Force
Watchdog: Temperature abort trigger set to 90c
Watchdog: Temperature retain trigger set to 80c
Device #1: GeForce 8500 GT, 256MB, 918Mhz, 2MCU
Device #1: Kernel ./kernels/4318/m2500.sm_11.64.ptx
Device #1: Kernel ./kernels/4318/markov_le_v1.64.ptx
Device #1: Kernel ./kernels/4318/bzero.64.ptx

[s]tatus [p]ause [r]esume bypass [q]uit =>
Session.Name...: cudaHashcat
Status.........: Running
Input.Mode.....: Mask (?l?l?l?l?l?l?l?l?l) [9]
Hash.Target....: TestAP (00:23:69:1e:38:c8 <-> 48:74:6e:5a5:cf)
Hash.Type......: WPA/WPA2
Time.Started...: Wed Mar 05 17:31:36 2014 (6 secs)
Time.Estimated.: 0 secs
Speed.GPU.#1...: 0 H/s
Recovered......: 0/1 (0.00%) Digests, 0/1 (0.00%) Salts
Progress.......: 0/5429503678976 (0.00%)
Rejected.......: 0/0 (0.00%)
HWMon.GPU.#1...: 97% Util, 76c Temp, N/A Fan

[s]tatus [p]ause [r]esume bypass [q]uit =>
Session.Name...: cudaHashcat
Status.........: Running
Input.Mode.....: Mask (?l?l?l?l?l?l?l?l?l) [9]
Hash.Target....: TestAP (00:23:69:1e:38:c8 <-> 48:74:6e:5a5:cf)
Hash.Type......: WPA/WPA2
Time.Started...: Wed Mar 05 17:31:36 2014 (13 secs)
Time.Estimated.: 0 secs
Speed.GPU.#1...: 0 H/s
Recovered......: 0/1 (0.00%) Digests, 0/1 (0.00%) Salts
Progress.......: 4096/5429503678976 (0.00%)
Rejected.......: 0/4096 (0.00%)
HWMon.GPU.#1...: 97% Util, 76c Temp, N/A Fan

[s]tatus [p]ause [r]esume bypass [q]uit =>
Session.Name...: cudaHashcat
Status.........: Running
Input.Mode.....: Mask (?l?l?l?l?l?l?l?l?l) [9]
Hash.Target....: TestAP (00:23:69:1e:38:c8 <-> 48:74:6e:5a5:cf)
Hash.Type......: WPA/WPA2
Time.Started...: Wed Mar 05 17:31:36 2014 (20 secs)
Time.Estimated.: 0 secs
Speed.GPU.#1...: 601 H/s
Recovered......: 0/1 (0.00%) Digests, 0/1 (0.00%) Salts
Progress.......: 12288/5429503678976 (0.00%)
Rejected.......: 0/12288 (0.00%)
HWMon.GPU.#1...: 97% Util, 76c Temp, N/A Fan

[s]tatus [p]ause [r]esume bypass [q]uit =>

Session.Name...: cudaHashcat
Status.........: Aborted
Input.Mode.....: Mask (?l?l?l?l?l?l?l?l?l) [9]
Hash.Target....: TestAP (00:23:69:1e:38:c8 <-> 48:74:6e:5a5:cf)
Hash.Type......: WPA/WPA2
Time.Started...: Wed Mar 05 17:31:36 2014 (23 secs)
Time.Estimated.: 0 secs
Speed.GPU.#1...: 601 H/s
Recovered......: 0/1 (0.00%) Digests, 0/1 (0.00%) Salts
Progress.......: 12288/5429503678976 (0.00%)
Rejected.......: 0/12288 (0.00%)
HWMon.GPU.#1...: 42% Util, 74c Temp, N/A Fan

Started: Wed Mar 05 17:31:36 2014
Stopped: Wed Mar 05 17:31:59 2014

C:\>


Any idea why is it so slow for WPA but for MD5 it runs ok ?