Re: How to protect 65816's 16MB Memory?

["Michael J. Mahon" <mjmahon@aol.com>]

Kelly Hall wrote:
> Scott Alfter wrote:
>
> > Expecting modern features to be present in nearly-20-year-old hardware is
> > insane.  You can sometimes add this stuff in later on, but hardware-based
> > memory protection wasn't something you'd see on PCs in the mid-'80s.
>
>
> Protected memory spaces are not a modern feature, being generally 
> developed in the 60s.  Granted, computers targeted at the masses have 
> always lagged on features because the target market is highly 
> cost-sensitive.

By the late 1980's, microprocessors could have easily included at least
some rudimentary protection mechanisms, if not paging.  But they didn't,
because, back then, microcomputers were not thought of in the context of
multiprogramming (for which protection is a real win), even though both
were commonplace in the mainframe/mini world since the mid-1960's.

This is yet another example of the micro world having to re-invent the
wheel twenty years later.  ;-)

It was not until the early 1990's, when RISC designers began to put
mainframe ideas on a chip, that the "mainstream" microcomputer industry
began to read the preexisting literature on supercomputers and parallel
computing to inform the much higher performance processors of the mid-
to late-1990's.

Competition, and the threat of one's own demise, "wondrously clears
the mind".  ;-)

> The 65816 was never designed for serious computing - it was a hack to 
> attempt to not lose the dwindling market for the 6502.  That said, I 
> really enjoyed my gs and wish I still owned it.

I have exactly the same opinion of the 65816.  There is a certain kind
of elegance to the 6502 architecture, but the 65816 extensions reek of
kludge.  (Come to think of it, the x86 has a similar relationship to
the 8080! ;-)

-michael

New Applesoft BASIC interface for NadaNet networking!
Home page:  http://members.aol.com/MJMahon/