What are some alternatives?
When comparing Core Temp and Sidebar Diagnostics, 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.
SpeedFan - Hardware monitor for Windows that can access digital temperature sensors located on several 2-wire SMBus Serial Bus. Can access voltages and fan speeds and control fan speeds. Includes technical articles and docs.
iStat Menus - "An advanced Mac system monitor for your menubar."
Real Temp - Real Temp is a temperature monitoring program designed for all Intel single Core, Dual Core, Quad...
Speccy - Speccy - find the details of your computer's specs. Great for spotting issues or finding compatible upgrades. Download the latest version free.