🚀 go-pugleaf

In article <4366ha$oik@lyra.csx.cam.ac.uk>, dpg1@cam-orl.co.uk (Duncan Grisby) writes:
|> In article <434ei3$ncu@oddball.sjc.MENTORG.COM>,
|>  ewill@hpewill.sje.mentorg.com (Eric Williams @ PCB x5577) writes:
|> > In article <42qclc$3bu@sashimi.wwa.com>, blackbob@sashimi.wwa.com (G) writes:
|> 
|> [...]
|> 
|> > |> Your analogy is worthless.  A supercomputer costs several million
|> > |> dollars.  Preemptive multitasking is no more expensive to  imple-
|> > |> ment  than  cooperative.  It might be cheaper, especially from an
|> > |> application developer's perspective.
|> > 
|> > PMT is (slightly) more expensive, because those systems that
|> > use it must also implement and require a method of
|> > synchronization between processes; CMT has built-in
|> > synchronization.  The Amiga Exec, for example, which had PMT
|> > from the beginning, had to implement signals and messages
|> > (and in v1.2, semaphores) in order to keep its processes
|> > from tripping over each other.  The programmer is required to
|> > learn this complexity (though actually it's pretty simple;
|> > Amiga Exec is very clean).  Unix also has signals
|> > and waiting in the kernel (as well as at the user
|> > level).
|> 
|> About the only significant thing an application programmer must
|> do, unless they are using shared resources, is make sure that
|> they don't do busy waits when waiting for events to occur. (Disk
|> access only really counts as a shared resource when processes
|> share a single file -- other accesses are looked after by the
|> OS.)

Actually, they shouldn't busy-wait anyway, even with shared
resources (if the resource has a semaphore, for example,
wait on that instead).  If the program must busy-wait, have
it do something useful (e.g. display update of a game could
check to see if a resource is available during vertical
blanking interval -- a bit contrived, perhaps).

|> 
|> As another feather in the Amiga's cap, the vast majority of its
|> kernel is re-entrant, allowing processes to be pre-empted during
|> system calls, unlike Unix.

And it all fits onto a half meg of ROM (actually 256K before
3.1) because of object oriented design techniques (before
C++ came).

Kind of makes you wonder whether our priorities can be
set straight.  It was a beautiful operating system run over
by the marketing bulldozer that we call Windoze, on a
nice machine that was just too pricey for the average Joe
BusinessUser (who wouldn't want it anyway, because too many
people would play games on it). :-)

|> 
|> -- 
|>  -- Duncan Grisby                                    --
|>   -- dpg1001@cam.ac.uk                                --
|>    -- finger dpg1001@cus.cam.ac.uk for PGP public key. --

-- 
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eric_williams@mentorg.com
My views!