This ran through my mind while writing a doc, may be dumb one.
I have seen people using the terms Microcode and Firmware in IBM system p world interchangeably.
Firmware update or microcode update
Is that right? Are they synonyms?
Yes, they are synonyms. IBM uses the term "microcode" for all sorts of what is commonly known as firmware, for reasons unknown. It is similar to Sun using the term "disk slices" for what is commonly called partitions, etc..
I hope this helps.
bakunin
As I understand it IBM use:
Firmware for the system embedded code - system firmware.
Microcode for the adapter and device embedded code - adapter microcode.
But all us normal people use either for either, typically firmware is used more often for both.
Um, yes and no 
Firmware is a piece of software for different kind of peripherals (routers, switches, ...). Microcode goes into the CPU, providing a slightly higher level or more complex commands based on the CPU's basic ("hard-wired") commands. For example, Digital's (R.I.P) VAX (R.I.P) used to have a microcode command to solve a polynomial.
pen
Thanks guys!!!