Yes . . . it misses a lot in prior to that back to wwii , but it's an interesting piece of the story.

 

What does he mean with "risky system" (little after starting) and "risk machines" (near de end)?

 

RISC, Reduced Instruction Set Computer. An architecture with a small number of simple instructions that are combined to create the effects of more complex instructions in CISC—Complex Instruction Set Computer—architecture.

Early on, there was the IBM 801 and the MIPS. Later the Motorola 88000 and PowerPC (Apple, IBM, Motorola collaboration, called AIM), today ARM and RISC-V

CISC processors have much larger instruction sets that combine many actions. The x86 is a CISC architecture family.

 

What does he mean with "risky system" (little after starting) and "risk machines" (near de end)?

I listened to last 3rd but didn't hear it.

RISC is what @Ya'kov explained. It was also a buzz word in the 1990s, lots of tech firms jumped on the bandwagon. DEC where Cutler worked were building a RISC device called the PRISM, destined to be the basis for new line of hardware from DEC. I believe Cutler and team worked on a new OS at DEC, named MICA, but partway through it was canceled.

That disappointed Cutler, Gates got wind of that and ended up hiring Cutler and team. A lot of Windows NT architecture was a reflection of MICA I believe. From the outset NT (and MICA) factored in RISC targets as a core requirement. The first version of NT ran on both x86 an DEC Alpha, a RISC chip that never really helped DEC survive.

Cutler said they supported both targets from day one of the coding, to force out issues and robustly ensure the code was processor agnostic as much as possible, had they done just x86 then tried to add DEC Alpha, that would have been much more effort.

Anyone seriously interested in OS internals should study the Windows Internals book, very detailed and makes it clear why Windows is in a different class to Linux and other Unix derivatives.