Have a look at the Recovery Console thread for additional info on text-based bootup. Basically, once the kernel is loaded and initialized, it passes control to /sbin/preinit, which does the rest. If you load the framebuffer console module (modprobe fbcon) early when preinit starts, you get to see the boot messages on the screen. For fbcon you'd need the power-kernel (v50 is the latest & greatest).