I'm not as interested in the 486; I went stright to the Pentium: https://www.righto.com/2025/03/pentium-multiplier-adder-reve...

I've been able to handle the Pentium with 3 metal layers. The trick is that I can remove metal layers to see what is underneath, either chemically or with sanding. Shrinking feature size is a bigger problem since an optical microscope only goes down to about 800 nm.

I haven't seen any chips with a solid metal top layer, since that wouldn't be very useful. Some chips have thick power and ground distribution on the top layer, so the top is essentially solid. Secure chips often cover the top layer with a wire that goes back and forth, so the wire will break if you try to get underneath for probing.

Those would be interesting chips to examine, if I ever get through my current projects :-)

Ok.

I'm speaking of e.g. the leap between the IBM PC in 1981 and the Compaq 386 five years later.

I wrote blitters in assembly back in those days for my teenager hobby games. When I could actually target the 386 with its dword moves, it felt blisteringly fast. Maybe the 386 didn't run 286 code much faster but I recall the chip being one of the most mind-blowing target machine upgrades I experienced. Much later I recall the FPU-supported quadword copy in 486dx and of course P6 meeting MMX in Pentium II. Good times.