During the VLSIlaboratory for design of semicustomchips at the department
Entwurf integrierter
Schaltungen (E.I.S.)
Frank Gerberding, Marc Zimmermann and I created a single instruction processor.
Its only Instruction is 'MOVE'. Since this instruction-'set' cannot be reduced
any further the chip is called URISC (= ultimative reduced instruction set computer).
Nevertheless, a memory-mapped ALU made this chip a complete computer:
Accessing special addresses (which are mapped to/from the arithmetic logical unit)
causes the ALU to run the desired calculations.
Ten pieces of this processor has been manufactured. One of these pieces is
shown in the two pictures on this page (I scanned it directly from slides, so
the quality is quite poor).
The internal calculations could have worked correctly with a clock up to 90MHz,
but unfortunately the I/O-operations are to slow, so the whole processor can be
run with a clock up to 50Mhz.