I never did the disabled loop thing. My special purpose O/S was of the
enabled sort; however, it did not use TSCH or STCH, it was in the SIOF
era. It is nice to see that CP optimizes the loop, so to speak.

Regards, 
Richard Schuh 

 

> 
> A TSCH loop is used when you are disabled for interrupts (and 
> don't feel like enabling) in response to CC=0 from SSCH.  CP 
> is smart enought to detect a TSCH loop and place the virtual 
> machine in a semi-enabled wait. 
> If you are enabled for I/O interrupts you issue a single TSCH 
> or STSCH *in the FLIH* to read and clear the interrupt 
> status.  The SLIH will typically drive a callback of some sort.
> 
> Alan Altmark
> z/VM Development
> IBM Endicott
> 

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