[Info-vax] LLVM, volatile and async VMS I/O and system calls

[Lawrence D’Oliveiro]

On Thursday, September 23, 2021 at 11:53:42 AM UTC+12, Jan-Erik Söderholm wrote:
> One very common case is where a variable refers to an "port" 
> on a microcontroller. The port is connected to some real life 
> equipment such as push buttons, relays or what ever. Those items 
> can be handled totaly out of control from the application code. 

This is memory-mapped I/O: those addresses don’t actually access real memory, and do not have normal memory semantics.

Some CPU architectures use special I/O instructions for this purpose, and won’t have this problem. This is why you have philosophical* debates about which is the better approach ...

*maybe even verging on religious