It was an essential utility to low-level format IBM PC and compatible hard drives with certain split HDD controllers like MFM and RLL before the advent of IDE.

It was an essential utility to low-level format IBM PC and compatible hard drives with certain split HDD controllers like MFM and RLL before the advent of IDE. It served a purpose on these drives+controllers where it (re)wrote track and sector layouts but could brick some of the transitional IDE-like hard drives that weren't meant to ever be low-level formatted. Later HDDs had no need for such a utility. It could also be done on some controllers from debug without any UI or sector testing like so: https://kb.iu.edu/d/aaoa https://kb.iu.edu/d/aaoa The advantage of SpinRite was it was a gold-plated tool for a specific purpose and could check for errors along the way.