This explains why I was taught to do “sync; sync; halt” in the late 80s, and still encouraged to do this in the late 90s at my first sysadmin job.
I’ve always wondered when and why this was no longer needed.
I started a Solaris sysadmin job in 2008 and was being taught “sync; sync; sync; halt” as late as that! My colleagues knew that you’re supposed to type each one out to let buffers flush, rather than all on one line, but it’s interesting that these old habits really do die hard.
(Prior to that job I’d only worked with Linuxen and BSDs.)