The Commodore 65 was a prototype of a faster C64 with Amiga like graphics and sound.
The Mega65 is a clone of the C65 with a 50mhz 4510 CPU using FPGA as well.
They should all share notes.
I think modern N64 emulators need at least a 2 GHz processor. (Less for ARM ala RPI, IIRC due to similarities in the instruction set.) And there's even an SNES emulator (BSNES) that needs >3 GHZ but it's schtick is that it aims to be completely accurate.
*Obviously these are not hard numbers. The point is the order-of-magnitude.
80's home computers are essentially lock-stepped multi-processor systems, where the CPU is just one processor, the others are (at least) the audio- and video-generator.
Especially the video generator can become expensive, since it needs at least be fast enough to generate a new line every 64 microseconds, and if the video generator has things like programmable resolution, color palette and sprites (which a lot of 8-bit home computers had), this can be quite a lot of "unpredictable" work per pixel.
Since all those 'special processors' ran synchronized per clock cycle, it is impossible or at least very hard to write efficiently multi-threaded emulators, since they would need to synchronize threads after each emulated clock cycle (it might actually be a bit easier for newer emulated systems where subsystems are often not synchronized that strictly).
Earlier emulators from the 90's often got away by skipping some of the 'cycle perfect' requirements and/or implemented some clever but complicated hacks which didn't really emulate the original hardware, that's why they could still run many games on much slower host hardware.
Funnily enough, there are some games that work on crappy emulators, but not on the accurate ones, until they get sufficiently accurate enough.
The what is a huge nuance, I personally think Zuckerberg would be able to create a device like this at this point in time.
While you were just comparing ages you accidentally bundled achievements and that's a big no no.
I'm gobsmacked. Maybe I gave up on my Apple II too soon!
There is also new software being written for the Apple 2 - take a look at Nox Archaist, for example: