[Info-vax] nice for VMS

[Arne Vajhøj]

JF Mezei wrote:
> re:
> 
> $loop:
> $goto loop
> 
>>>>>> Try it on a GS1280. Runs closer to 60% of one CPU.
> 
> When that process isn't consuming CPU, what would be its process state
> if it is waiting for memory ?
> 
> For IO, VMS is fully aware of the process having made an IO request and
> waiting for results, so it puts the process in LEF and moves on to
> another process.
> 
> However, if there is a wait for memory, how would this work ? VMS
> wouldn't be aware that the process is waiting for memory, but the CPU
> would be. Do the wildfire/GS class of machines have the ability to
> signal to VMS that the process is waiting for memory so that VMS can
> switch to another process in te meanwhile ?
> 
> Or does the process remain in COM status all along, and the 40% of CPU
> cycles are wasted while that process waits for memory ?

Since changing the process state would require writing to memory,
then I can not see the point.

> While I am at it, if you request to load 8 bytes from memory into a
> register, can you really swap process context while you are waiting for
> that memory ? When that memory request completes, you can't just let the
> contents be deposited into a register that belongs to another process at
> the moment.

I don't think it can. I would expect all instructions in the instruction
stream to either be not started or completed. Else PC would not need to
have decimals.

Arne