C integral types [was Re: Semi-OT: Why Kids Can't use Computers] (fwd)

[Lennart Sorensen]

On Mon, Aug 19, 2013 at 10:48:29PM -0400, D. Hugh Redelmeier wrote:
> The 386 was introduced in 1985.  PCs using it came out in 1986.
> 
> OS/2 was first released in December 1987, but probably wasn't useful
> (text mode only, ...).  Released a year later, 1.1 had a GUI.

Many voice mail systems and such ran on it.

> So if you wanted to run OS/2, you probably had a 386.  It would
> happily run as a 286.  Most 386s spent their lives emulating 8086s and
> perhaps 80286s.
> 
> PC hardware was cutting edge because that was where the competition
> was.

Well in many ways PC hardware was far from cutting edge.  It was just
improving quickly in many ways.  It took many years for the PC to get
anywhere near the hardware capabilities for sound and graphics that the
Amiga or even most game consoles at the time had.

> PC operating systems were real lagards because there was no
> competition.  I realize that word is ambiguous.  There certainly were
> a reasonable number of competing OSes (i.e. competition) but the
> actual struggle was so one-sided that it didn't appear to be a
> competition.
> 
> Reasonable choices of OS for PCs over the years.
> 
> - DOS
> 
> - From Digital Research: CP/M 86, MP/M (multitasking version), DrDOS
> 
> - UCSD Pascal
> 
> - various genuine UNIXes (quite a few good ones once the 386 came
>   out).  Xenix worked well on 286s (I ran it on an 8086).
> 
> - UNIX clones: Coherent, Whitesmith's Idris, Minix, and others I've forgotten

Did SCO or unixware ever qualify as good options?

> - BeOS

That was never a reasonable choice for anything.  Designing a new OS
without multiuser or security taken into consideation at all was just
amazingly stupid.

> - modern UNIXes: *BSD, Linux, OSX, Solaris

I have dealt with Solaris x86, and it wasn't pleasant.

> After the 68000 became viable, when was an 8088 considered for a new
> design of a personal computer that was not meant to be PC-compatible?
> I guess we don't actually know.  But if you judge by design wins, I
> cannot remember any.  Unfortunately, I don't think that the 286 won
> any either, so it really doesn't make my point.

Hmm, the Ontario goverment 'Icon' systems ended up picking the 80186,
and they were not intended to be PC compatible.  Not an 8086 or 8088,
but related.

> | I have written MMU code for the 386.  What a mess.
> 
> In what way?

16 bits of the address go in one part of the data structure, the
next 8 bit somewhere else, and the last 8 bits in yet another place.
Very obvious that every time they extended the address range, they threw
it at the end and didn't ever think that maybe we will need to do this
again so we should reserve room for the future.  The x86 is just garbage
design pilled on top of garbage design for decades.  I haven't dared
look where the new 32bit for amd64 ended up.

> The original ARM MMU had a serious problem.  The cache was tagged with
> virtual addresses.  So when you changed the MMU, you had to flush and
> invalidate each cache entry.  Oh, and flushing, as befits a RISC
> design, took a lot of instructions (one for every cache element?).
> That made process switching, if it involved an address space switch (as
> in Linux) quite expensive.

Yes the original ARM had some issues, but they seem to have been willing
to fix them.  The original FPU was horrible too, and they have replaced
it with a new, totally incompatible by sane design.

Whenever intel decides to thrown away the old and do something better,
they end up creating something even more awful (like the Itanium).

-- 
Len Sorensen
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