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This jumped out at me, as a new meaning to the idea of disassembling microcode:
Quote:
For the back end machine we chose a very interesting microprogrammable minicomputer, the Digital Scientific META-4, a new machine (1969). By the time our META-4 arrived my simulation was finished and we were well into the code on the 1108.
Because I love hardware I immediately latched onto the META-4. I decided to implement some additional instructions in microcode, ones I thought would speed up database processing. To microcode the META-4 one first disassembled the microcode store, which consisted of a sandwich of glass plates with small metal foil squares glued on to implement the codes. The reason for this arcane arrangement was because the macrocode store needed to be very fast, and core memory and other read-only memory implementations were too slow. After disassembling the store, one removed or added metal squares corresponding to the bits of the desired instructions. The machine came with a generous supply of little squares, conveniently provided with an adhesive backing.
From the
very interesting career retrospective blog of Rudd Canaday, the fourth and little-known member of the team who invented UNIX.
Next paragraph:
Quote:
It turned out that the microcode idea was not a good one. My special instructions did not make any perceptible difference in the speed of our system. However, I had fun.
More about the machine
here.
Attachment:
Meta-4-system.png
