Re: nice for VMS

Richard B. Gilbert wrote:
JF Mezei wrote:
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 ?

If your memory is aligned properly; e.g. the three low order bits of the address are 0, a load of 8 bytes should go quickly. If they are not 0, the O/S will do its best which, admittedly, is not very good. ISTR that it must move the eight bytes to properly aligned temporary storage and then load them into a register! This takes many cycles longer than a properly aligned quadword load. The compilers know how to do it right but if you use Macro and fail to align things properly, your code may run like a dog!

Most HLL compiler allow you to specify that data should not be
natural aligned. And take the performance hit, which even at older
Alphas could be >x10.

Arne
.

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