Joel C. Ewing wrote:
I think you mis-interpreted John's remarks. He didn't say anything about mainframe developers extensively writing and testing microcode instructions (which is not a documented user interface), but instead extensively writing and testing z-Architecture assembler code (with the High Level Assembler, which uses instructions documented in the z/OS Principles of Operation, which IS a documented user interface). Outside of IBM, microcode assemblers might be used in a limited educational setting in conjunction with emulated execution to demonstrate principles of microcode development - they would not be used to generate and modify microcode on an actual IBM mainframe processor.
Microcode???!! I suggest you read this article: http://researchweb.watson.ibm.com/journal/rd/483/heller.html
Then, with your enhanced understanding of how modern mainframes work, go back and re-read the posts in this thread.
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