In my previous post about Modcomp, I mentioned that -- as far as I know -- they were the only mid-70's computer company that routinely revised its computers by replacing chips and rewiring wires. All of Modcomp's competitors made upgrades and hardware fixes by replacing entire boards. (We're talking foot-square boards, there was less miniaturiation in those days.) Modcomp's approach was much more flexible and dynamic, but -- let's be frank -- it was wrong.
First, as I mentioned, Modcomp issued corrections every week. At that torrid pace, you have to suspect that they were introducing problems as fast as they fixed them. There could not be time to run careful tests on each week's combination of fixes before publishing them. Even if the fixes were good, they still had to be performed correctly on your computer. You had to hope that every wire was rewired correctly, and it's easy to attach a wire to the wrong pin.
Second, Modcomp had to perform most of the wiring changes for its customers. They paid a lot to get the rare people who knew how to do this fieldwork and were willing to travel, and to try to be deadly accurate. Paying maintenance guys to swap boards was cheaper, simpler and safer, and required far less qualified people.
Now here's an interesting note. Our company agreed on a set of critical changes with Modcomp that required an entire forty hours of rewiring. They sent a young woman to us, to make these changes. They told us they had learned that men were too impatient to do a lot of rewiring accurately. All their top repair people were women.