21. Four revisions of the chip exist, each physically identical but with different microcode . 22. On the HP 3000, this decision took extra microcode cycles in every instruction. 23. The microcode level that specified four bit tags was referred to as level Gamma. 24. The 2903 used microcode to emulate 1900 hardware. 25. This microcode specification became known as level Gamma. 26. It is thus somewhere between the role of microcode and of a hardware emulator. 27. Even for real microprocessors, machine-language instructions may be implemented by microcode . 28. The E Box executed all instructions, including floating-point instructions through microcode . 29. In 1972, Shustek proposed using microcode for evaluating the performance of computer systems. 30. Microcode is software embedded in a chip.
