To address the other side of the issue, I do not use AMD overdrive, at all. I use CoreTemp, which a lot of experienced builders and overclocking "gurus" that I relate to, as well as from my own comparisons, seems to be the most accurate utility, but HWinfo (NOT HWmonitor) generally has identically accurate (IF accurate is even the right word, let's just say "comparatively accurate".) sensor reading to CoreTemp.
I'd use Prime95 v26.6, which does NOT run AVX instructions, and therefore does not create unrealistic temps. Prime 26.6 is the best currently available utility for creating steady state thermal testing loads. Other versions of Prime use AVX instructions and create unrealistic temps.
Regardless of architecture. P95 v26.6 works equally well across all platforms. Steady-state is the key. How can anyone extrapolate accurate Core temperatures from workloads that fluctuate like a bad day on the Stock Market?
I'm aware of 5 utilities with steady-state workloads. In order of load level they are:
(1) P95 v26.6 - Small FFT's
(2) HeavyLoad - Stress CPU
(3) FurMark - CPU Burner
(4) Intel Processor Diagnostic Tool - CPU Load
(5) AIDA64 - Tools - System Stability Test - Stress CPU
AIDA64's Stress CPU fails to load any overcloked / ovevolted CPU to get anywhere TDP, and is therefore useless, except for giving naive users a sense of false security because their temps are so low.
HeavyLoad is the closest alternative. Temps and watts are within 3% of Small FFT's.
Run it for ten minutes on Small FFTs. NOT large. NOT blend. SMALL. Ten to fifteen minutes, fifteen is probably where I'd stop if thermal testing is the only thing you're currently trying to establish. For stability, the same test, for 15-24 hours, to determine as much as possible, that you have a pretty much entirely stable overclock. I've seen chips error out between 15-24 hrs so a 24hr run is necessary if you want to be as sure as you realistically can be.
For testing stability between steps, an hour is fine, followed by a full run before you call it good.
Prime95 v26.6:
http://windows-downloads-center.blogspot.com/2011/04/prime95-266.html