Which diagnostic tool requires downloading from GSX and works on a limited number of models?

The correct answer is Apple Service Diagnostic. This tool is specifically designed for use by Apple technicians to perform thorough testing on Mac hardware. Unlike some other diagnostic tools that come pre-installed on Macs or are available for broad use, Apple Service Diagnostic must be downloaded from the Global Service Exchange (GSX) and is only compatible with a select range of Apple products.

Apple Service Diagnostic allows technicians to evaluate the hardware components of supported models, assisting in the identification of any issues that might require repair. The limitation to certain models is important, as it ensures that the diagnostic procedures are tailored to the specific hardware configurations present in those models, providing accurate and efficient troubleshooting.

On the other hand, Apple Diagnostics and Apple Hardware Test are built into many Macs and can be used without any special downloads. Mac Resource Inspector is a utility that provides information about Mac hardware but does not function as a diagnostic testing tool in the same capacity as Apple Service Diagnostic.