Access your miner over the web browser.
Go to the "Settings".
Scroll down to the bottom of the page and click on "Export".
Open the exported file (miner.json). File can be opend with the Windows Word Pad.
The first two options you see are "auto_frequent":"0","frequency":"900"
Set the "auto_frequent" from 0 to 1
Set the "frequency" to 950/1000/or what ever you want.
Save and close the file.
Access your miner over the web browser.
Go to the "Settings".
Scroll down to the bottom of the page and click on "import".
Choose the file miner.json.
Wait till it's done. You get a message that tells you that it's done.
The miner reboots.
Wait a few mins and then check if it's working.

More Infos here:
https://bitcointalk.org/index.php?topic=5038441.msg46842719#msg46842719