You are correct, this is a representation of the number of instruction in flight at any one time. That number is rather imprecisely known because just counting all the queue depths does not indicate that any specific code could keep all those queues full.
The machine can dispatch one group of up to 5 instructions per cycle which limits average completion rate as well.
There's lots of details here:
Power4
The Power 4/5/6, 970 & Cell processors use VHDL.
At least some of the "Star" line of RS6K processors used VHDL as well.
Some earlier Power/PowerPC microprocessor designs used a proprietary internal IBM language.
Please don't forget IBM's AS/400 (now iSeries) machines. They went 64-bit in 1995 as well (but, more desk-side than desk-top).
Due to their unique system architecture, which distributes code in an object-oriented intermediate format, users who bought a 64-bit system immediately had the full benefits...even on their old code. I.E. same performance as a re-compile, but without access to source.
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The machine can dispatch one group of up to 5 instructions per cycle which limits average completion rate as well. There's lots of details here: Power4
The Power 4/5/6, 970 & Cell processors use VHDL. At least some of the "Star" line of RS6K processors used VHDL as well. Some earlier Power/PowerPC microprocessor designs used a proprietary internal IBM language.
Please don't forget IBM's AS/400 (now iSeries) machines. They went 64-bit in 1995 as well (but, more desk-side than desk-top). Due to their unique system architecture, which distributes code in an object-oriented intermediate format, users who bought a 64-bit system immediately had the full benefits...even on their old code. I.E. same performance as a re-compile, but without access to source.