A modern x86 CPU built out of TTL logic would be huge, slow and use lots of power. Comparing number of transistors:
- 6502: 3500 transistors[1]
- Intel Core i3: 382 million transistors,[2] or roughly 191 million transistors per core.
So a single core of a modern x86 processor built with TTL would have 55,000 times the number of chips of a TTL 6502. Most people wouldn't have the space, power or cooling capacity to run that.
Also, it would be much slower than a single chip x86 CPU, since it takes time for signals to travel between discrete chips, due to having to drive the capacitative loads of the I/O pins (and traverse a much larger distance). There's no way that TTL could run at gigahertz clock rates.
The only reason why a 6502 made of TTL can be faster than a real 6502 is that the 6502 was a very slow processor. Its clock speed was only 1 - 3 megahertz.[1]
I don't think you need to keep all the cache.The cpu will be much slower due to the slower chips and propagation delays so it will be much better matched to memory speeds. Which would make cache misses much less important.
It even boots up in a VIC20, and can run at 20x the clock speed of the real 6502.