What are some alternatives?
When comparing SpeedFan and AIDA64, you can also consider the following products
Open Hardware Monitor - Monitors temperature sensors, fan speeds, voltages, load and clock speeds, with optional graph.
CPU-Z - CPU-Z is a freeware that gathers information on some of the main devices of your system : Processor name and number, codename, process, package, cache levels.
Speccy - Speccy - find the details of your computer's specs. Great for spotting issues or finding compatible upgrades. Download the latest version free.
iStat Menus - "An advanced Mac system monitor for your menubar."
SIW - SIW is an advanced System Information for Windows tool.
Core Temp - Nov 4, 2017 - Core Temp is a compact, no fuss, small footprint, yet powerful program to monitor processor temperature and other vital information.