Delete comment from: Ken Shirriff's blog
| Would love to hear about the plated/etched memory
| used for "microcode" in the 360/67 back in 1970.
That was used for the 360/30 and the 360/40 as well (1965 and later). I saw the "microcode" for each of those CPUs being updated (the /40 several times). Something of the sort was also used with the 360/50, although I never saw it out in the open, so I can't say that it was the same underlying technology (possibly not). Of course, the 360/65 had the exact same thing as your 360/67 (basically the same box and cards). On the other hand, the 360/75 was hardwired: so, no microcode existed for it at all. Much of the 360/40 microcode was "written" (by coloring in squares on a coding sheet or template-type form) by Dr. Peter Calingaert, one of my professors at UNC Chapel Hill Dept. of Computer Science (who had been hired away from IBM by Dr. Frederick P. Brooks, my thesis advisor). Dr. Calingaert also wrote all of the microcode for the decimal arithmetic instructions for all of the original System/360 CPUs (for those that needed such microcode). Long ago (1967ish) I had pictures of updated, replacement plastic sheets being "sorted" into the stack, by hand; there's no telling where they are now (54 years later). I have seen within the past decade pictures of it online somewhere (and I may have downloaded some. I'll look and post what I find.
Feb 1, 2021, 5:07:36 PM
Posted to IBM paperweight teardown: Reverse-engineering 1970s memory chips