What do you mean by discussion about software? Is the readership primarily programmers or is it software end-user discussion? Having a clear idea about your user base is step one, and I think that should be easy for you.

How many uniques per month are you seeing?

Have you considered video? You'll need to find that balance between user-experience and monetization.

Like someone else mentioned, you might want to consider looking into a proper Ad Server setup where you can then tap into the programmatic ad exchanges/networks and get more bang for your buck. DFP Small Business may be best - it's free up to XX million imps and you can manage AdSense through it as well.