ZX81 memory troubles

[RetroTechie]

No, Zero Insertion Force refers to a socket where you don't have to push onto an IC to get it into a socket. Like the kind with a lever you see on PC mobo's (drop CPU into place, pull down lever), or the type you usually see on EPROM programmers.

That's not the case here (you're still pushing the IC into its socket, and it takes some force). As for contact area, a small area of reliable contact area is still a better contact than large but corroded area. Point is, put IC into a turned pin (gold plated) IC socket, and the contacts hold. For decades if needed. Do the same with a low cost IC socket, and it USUALLY does the same. Also turned pin IC sockets do better with repeated insertion / removal.

The more important questions are a) whether they're worth their higher cost (depends on the use), and b) if it's not better to solder an IC directly into a board (usually yes, unless you expect end-user to replace IC's). My choice usually goes:

* Quick experiments, 'throw away' circuits -> low cost IC socket. IC usually costs more than socket, IC replacement is easy. When done, pull IC's & possibly discard the experiment board. What you're throwing away is cheap junk, you keep the rare/expensive parts.
* If I want it to last, and expect to exchange IC's later (ZX81 ULA / Z80 / ROM / RAM is a good example) -> turned pin IC socket.
* If I want it to last, and don't expect to exchange IC's later (like for repairs, when repaired machine goes back to original owner) -> solder IC directly into the board.