[Info-vax] nice for VMS

[Bob Koehler]

In article <002ae1a9$0$18038$c3e8da3 at news.astraweb.com>, JF Mezei <jfmezei.spamnot at vaxination.ca> writes:
> Bob Koehler wrote:
> 
>>    There are a variety of states related to memory management, including
>>    PFW, COLPG, and others I could dig up somewhere.
> 
> But virtual memory management is under the responsability of the OS. But
> waiting for 8 bytes of physical memory to be loaded into a the register
> is very much hardware based and would the OS be aware of this operation
> taking a long enough time to warrant a switch processing to another
> process ?

   No.  If the transfer is between the CPU and RAM then it is part of
   instruction execution and on Alpha is not interuptable, on VAX is
   only interuptable for some of the more complex instructions like
   MOVCx.

   If the transfer is between an I/O controller and the memory then it
   is most likely a DMA and the OS won't be involed until the DMA
   completion interrupt occurs.

   I think in the case being discussed, we were talking about finding a
   label in a DCL script that has aleady been found earlier and isn't 
   far away.  That could involve an I/O, or just a reference to a
   buffer.