Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!cs.utexas.edu!sun-barr!ccut!wnoc-tyo-news!rena!lkbreth!trebor
From: trebor@lkbreth.foretune.co.jp (Robert J Woodhead)
Newsgroups: comp.arch
Subject: Re: Adding fire to the segmentation flamefest...
Keywords: segments suck
Message-ID: <9244@lkbreth.foretune.co.jp>
Date: 5 Apr 91 01:49:37 GMT
References: <9234@lkbreth.foretune.co.jp> <45180@super.ORG>
Distribution: comp
Organization: Foretune Co., Ltd.  Tokyo Japan
Lines: 36

rminnich@super.ORG (Ronald G Minnich) writes: (in response to a msg by me)
>Even the most basic Unix systems use segmentation, whether or not
>the architecture they run on is a segmented architecture. Segments
>are a way of grouping things. I can't see that going away. 

Ron, the point is not whether segments can be useful -- they can.  The
point is that quite often they can be a royal pain in the nether regions,
and thus, they should not be imposed by the hardware.

"Objectionable segmentation" is that imposed by the hardware (eg:INTEL).
"Good segmentation" is that imposed by the software (OS) (eg:virtual memory).

For example, consider the proposal that was made in a recent message on this
topic, for a 32 bit segment and 32 bit address.  If that was implemented in
the memory system (so that the cpu goes "duhh, here is a 64 bit address,
gimme my memory, dude!") then you get the best of both worlds; you can treat
your memory as a 64 bit address space, or you can have up to 2**32 segments
2**32 bytes long, or you can have segments >2**32 bytes long that just happen
to be set up as 2 or more contiguous segments by the OS.  The only restriction
is that when a program asks the OS to allocate a new segment, it's gonna get
a pointer back that is on an 2**32 bit boundary in the virtual address
space.  And since it's all virtual memory anyway, that's not a problem.

Now, in the real world, we may not get there overnight, because of the obvious
tradeoffs that hardware designers make.  But for us software people, flat
address spaces are "a good thing".  And having to work on segmented machines
ala INTEL is an exercise in torture.  Although there are worse machines; you
wouldn't believe the shenanigans the hardware designers inflict on Nintendo-
level programmers to save 5 cents per machine in costs -- and I have to
design an object oriented system for one of them!  Ye gods!

-- 
+--------------------------------------------------------------------------+
| Robert J. Woodhead, Biar Games / AnimEigo, Incs.   trebor@foretune.co.jp |
| "The Force. It surrounds us; It enfolds us; It gets us dates on Saturday |
| Nights." -- Obi Wan Kenobi, Famous Jedi Knight and Party Animal.         |