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From: John Savard <quadibloc@servername.invalid>
Newsgroups: comp.arch
Subject: Re: Privilege Levels Below User
Date: Sun, 09 Jun 2024 09:14:11 -0600
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On Fri, 7 Jun 2024 20:40:34 +0000, mitchalsup@aol.com (MitchAlsup1)
wrote:

>Are Supervisor Calls "brnches" since they go to controlled entry 
>points??

Well, they're a kind of subroutine call. But they're really
instructions that initiate the computer's response to an interrupt,
which is what makes the entry point controlled and the instruction
able to increase privilege.

>How are you going to perform elementary functions {SIN, COS, EXP, LOG}?

Just because the feature exists doesn't mean it needs to be used for
everything. Ordinary subroutine calls will still exist, so if these
routines require scratchpad memory, that will be fine.

>A C compiler is an application running in a different process. Why
>is a JIT "not like that" ??

A C compiler doesn't save data in memory that can then be executed. It
writes to a file. The linking loader, instead, is "like" a JIT
compiler in that respect.

John Savard