They were working with code that already pretended to be in protected mode anyway (with the exception of locking and unlocking blocks of memory... which was unnecessary with a hardware MMU.)
Even saying that, it was amazing at the time to run essentially unmodified 'real mode' binaries in protected mode. (There was a tool that would take an existing binary and set the 'okay to run in protected mode' flag.)
yeah, they go into that in the referred-to book (The Personal Computer from the Inside Out).. though spectacularly irrelevant in this day and age, it still makes a thrilling read, for me anyway ;)
It does me too... I was an early high school computer enthusiast/programmer around this time, and remember waiting for Windows 3 with bated breath. At the time, I didn't appreciate the engineering and politics behind what went into Windows 3, and it's fun to look back on it all in retrospect.
I never liked the product as much, but the same thing's true for me for Windows 95. I remember waiting years for it, and then all the drama around Schulman's work to try to uncover _undocumented_ API's that Microsoft was reserving for itself to give its software an advantage. The AARD code is about all I remember of that that was real. (And of course now, Apple has undocumented API's all over its products, and it doesn't get nearly the press that that did then.)
Even saying that, it was amazing at the time to run essentially unmodified 'real mode' binaries in protected mode. (There was a tool that would take an existing binary and set the 'okay to run in protected mode' flag.)