Via Raymond Chen, Eric Shlaepfer built a 6502 emulator out of full-size components:
The MOnSter 6502
A dis-integrated circuit project to make a complete, working transistor-scale replica of the classic MOS 6502 microprocessor.
How big is it?
It's a four layer circuit board, 12 × 15 inches, 0.1 inches thick, with surface mount components on both sides.
Can you hook it up inside an Apple ][ and run Oregon Trail?
No, not directly. It's neat to think of plugging the MOnSter 6502's in-circuit emulator (ICE) in-circuit replica (ICR) cable directly into a socket inside an Apple ][, but that wouldn't actually work. The Apple ][ design relies on a number of clever tricks that derive timing for video generation and peripheral control from the main clock signal — all of which will fail if you need to run at a slower speed.
Are you going to make one out of vacuum tubes next?
Make sure you watch the 2-minute video.