For me, for the past month or so, I've been modifying a rare Sanyo MBC-775 to accept 640K of memory. (It normally has 256, but I figured installing sockets would help me or anyone in the future replace bad memory.) I've been having to map out the memory connections, though, because although this system seems to have been made for later models of Sanyo IBM clones, not all of the connections, from forgotten traces in manufacturing and design, are in place, so it also uses patch wires.
Today, though, I was able to desolder the RTC/CMOS chip off of my Compaq Portable III's motherboard (I used a heat gun along with a chip puller) and add a new socket in, as well as buy a power module to futureproof the battery. (The module I bought has a battery holder on it, which replaces the original blocky dual-cell battery.)