Linaro has many tuning works on Hikey, for example you can refer Steve Muckle's presetation for CPUFreq governor benchmark profiling on Hikey: http://connect.linaro.org/resource/las16/las16-307/. From my understanding, Steve's work usually has enabled thermal management frameworks.
I guess you are looking for the CPU max capacity without any constraint for CA53 on Hikey, and do some comparison with another board's CA53 so you want to get straight performance evaluation for one specific CPU type, is this your case?
If so, I place one heat sink on SoC and use a fan to help dissipate heat, usually I use this method to verify software optimization without any constraint by thermal. Please note, this method still let the SoC very heat and may harm your board. IIRC, Hi6220 has hardware mechanism to automatically trigger reset if temperature reach 90'C. So if you have high ambient temperature, it's possible still to trigger reset board.