Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!decwrl!pyramid!prls!philabs!spies!ssdis!gsarff
From: gsarff@ssdis.UUCP (gary sarff)
Newsgroups: comp.sys.amiga
Subject: Re: Amiga UNIX
Message-ID: <134@ssdis.UUCP>
Date: 8 May 88 21:33:31 GMT
References: <211@laic.UUCP> <3663@cbmvax.UUCP> <1872@sugar.UUCP> <4928@sdcsvax.UCSD.EDU>
Organization: Special Security Department, Internal Security
Lines: 33
Summary: Amiga has virtual memory since when?

In article <4928@sdcsvax.UCSD.EDU>, hutch@net1.ucsd.edu (Jim Hutchison) writes:
> 
> Virtual memory, yes, the Amiga has it right now.  Each process sees a linear
> address space based at 0, which is not based at physical 0.  This is one
> form of virtual memory.  If you take this and add swapping, you have a memory
> management system which will handle pre-paging unixes.  This takes you up
> through various system V releases, but not the recent ones.  Paging is still
> a nice preformance improvement, and *I* prefer the Berkeley "hacks" to the
> purity of the AT&T "features".
What?
The amiga does scatter loading of executable images into its free RAM.  this is
not the same to me as virtual memory, and all the processes are in the SAME
address space, (along with the OS itself).  Real virtual memory would
give each process ITS OWN address space starting at some point (zero say).
"Each process sees a linear address space based at 0..." How does the process
"see" this?  Chances are on a busy amiga, it won't even get loaded into the
same place(s) in RAM two times in a row, if a program prints the address of
some memory structure, it will probably be a different address.  In a virtual
system it would always be the same, today, tomorrow, and next year.

> Still there are always compatibility libraries.  If I don't here of one  
> by then, I will be doing fork()/wait() with tasks in the not so distant
> future.
Good luck, I hope you can do it.  I've been trying to do fork() on a protected
mode non-unix OS at work that, unlike amigados, does keep track of resources
given to a program, such as files open, memory/devices allocated, etc. and it
is still a pain.  Maybe under ARP that does do resource tracking, under
amigados, it would be harder.
-- 
Gary Sarff           {uunet|ihnp4|philabs}!spies!ssdis!gsarff
To program is human, to debug is something best left to the gods.
"Spitbol?? You program in a language called Spitbol?"
  The reason computer chips are so small is that computers don't eat much.