The i386/stand directory holds functions that are useful, but cannot be called from the kernel. For example printf() is great, but if the kernel called printf() it would generate a TRAP and wind up back in the kernel.

The functions here emulate these functions by dealing directly with the hardware on the system.

The 4.3BSD Internals book by Leffler, McKusick, Karels and Quarterman covers machine-independent stand functionality in:

Chapter 13.2, pg 394 Bootstrapping.