Table of contents

Motorola 68000

Each 68000 micro-instruction consists of a 17-bit sequencing field and a 68-bit action field (85 bits in total). These are stored in two separate sections of the microprogram ROM (what other sources call the "microcode" and the "nanocode"). The sequencing field specifies the next microcode address based on various branch conditions, while the action field controls the various parts of the CPU.

Motorola 68000 Microprocessor: This is a heavily microcoded Microprocessor with a large main array approximately 70 bits wide. It would be difficult to test the microcode by a series of microprocessor instruction, so instead a special combination at the Interrupt pins places the chip into a test mode and the microcode data is output on the chip’s 23 address lines. This is done as three passes for a total of 69 bits. (Internally there may have been an “A0” pad so that would have been 24 address lines x 3 = 72 bits.)

(source: comment hackaday.com/2012/08/13/taking-a-look-at-decapped-ics/#comment-734991↗ )

XT/370

ARM Jazelle DBX

Jazelle DBX (direct bytecode execution) is an extension that allows some older ARM processors to execute Java bytecode in hardware as a third execution state alongside the existing ARM and Thumb modes.

PowerPC

* sci-hub.se/10.1109/test.1994.527980↗ The PowerPC 603 microprocessor: an array built-in self test mechanism

BCM Videocore

Raspberry Pi BCMs:

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