[Info-vax] Compatibility and 64-bit

[JF Mezei]

On 15-03-15 18:59, Stephen Hoffman wrote:

> Everything is defined at compile time, certainly.  On OpenVMS Alpha, 
> all virtual addresses are 64 bits, and always have been.  That means 
> that pointers are either 64-bit addresses, or they are 32-bit addresses 
> that get sign-extended to 64-bit addresses. 

If 32 bit addresses are used in the code, does it get extended to 64 bit
by using different machine instrunctions that fill the missing 32 bits,
or is there some sort of "switch/flag" in the process that tells the CPU
to only look at first 32 bits and sign extend it to 64 before making the
request to the virtual memory system ?