Apple’s Prototype Copland OS Booting
This was intended to be Mac OS 8, a microkernel (called NuKernel) based OS that would finally modernize Apple's aging technology stack. It failed, although several of its user-oriented components made their way into later versions of the OS (both Classic and OS X).
This is booting off a PowerMac 7600/66 AV, but connected to a Dell LCD monitor so you don't have to see the refresh. It boots to the "Z Theme" which was a little silly. During start-up you can see a very unique splash animation, and various hardware being identified and initialized.
Copland was to contain a "blue box" emulation layer for classic Mac apps -- a concept that would later be re-used as "Classic" in Mac OS X -- while next-generation apps would be optimized for the PowerPC CPU.