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Re: Problems in "Modernizing" a //gs
bjblackbear@ibm.net (B.J. Major) wrote:
>I discussed this notion of what it would take to upgrade or
>"modernize" an Apple IIgs with a programmer/engineering friend of
>mine in Australia. His thoughts on the subject appear below in quotes.
>If you disagree with him or have other thoughts on the subject, you
>should contact him directly via his web page address instead of
>emailing me. I'll only mention here that he's one of the most
>brilliant computer minds I know, does programming for a living, and
>also does custom hardware design on the side. In other words, he's
>an all-around technical genius.
I see he programs for OS/2 and thus for the Intel architecture. I'm
surprised he would feel this way considering the Pentium has evolved
from the 8-bit Intel 8080 and we don't think of the Pentium as
"basically an 8-bit CPU at heart." Let me see what's wrong with his
reasoning.
>====================================
>>Hmm. I hate to sound like a wet blanket, but if the 65832 is
>>pin-compatible with the 65816 then it is still basically an 8-bit CPU
Here's the problem. Who said the next generation 65816 would be pin
compatible? It would only have to be instruction compatible! A
Pentium evolved from an Intel 8080 and it is _not_ pin compatible with
an 8080 or even an 8086. This one assumption faults his whole premise.
>>with some 16-bit features. The 65816 was not very powerful; the
>>systems that used it to best effect (eg. Super Famicom) got their wow
>>value from exciting custom graphics and audio ICs, not from CPU
>>horsepower. The 68000, clock for clock, is substantially more
>>powerfulthan the 65C816 used in the IIgs.
_Not_ in all situations. In integer multiplication and division, yes,
but the 65C816 is much more efficient at handling memory. It can
access memory in a single cycle whereas the 68000 needed 4 cycles. In
a sense, the 65C816 is 4 times as efficient as the 68000. Western
Design Center also claims it has some RISC like features. It is true
that in integer multiplication and division, the added overhead of
breaking down such tasks into addition and subtraction would negate
this advantage, but for many tasks, the 65C816 can hold its own against
a 68000 of a _higher_ MHz rating. That's why a stock GS can match a
Macintosh Plus or an Amiga 500 in performance in real world tasks like
word processing. That's wp as in graphical word processing under
AppleWorks GS, btw, using TrueType fonts and printing to the same type
of high resolution printers as the other computers.
Similarly, I clocked a Macintosh LC '020 running at 16MHz against a
GS running at 9MHz and found that the GS came was consistently faster
at tasks such as scrolling through a word processing document, sizing
a page to fit in a page layout program, find and replace functions,
etc. I use a '25MHz PC and a 13.75MHz GS and this speed GS is faster
for word processing tasks than this speed PC. Again, hat's wp and
page layout as in graphical word processing and desktop publishing
under AppleWorks GS, using TrueType fonts and printing to the same
type of high resolution printers as the other computers. And you
can't say the Mac LC was slowed down by a "modern" integrated
software either, because I was using an early version of Microsoft
Works for the Mac, published in the '80s. The features were same
as (and in some cases even less than) AppleWorks GS'.
>>
>>I daresay that a reasonably powerful PowerPC machine running an
>>emulator will be able to emulate this "mystery 65832" at three or
>>four times the instruction rate speed, and at least an order of
>>magnitude higher thruput than the actual hardware.
Real world results disprove this conjecture. The "Bernie II" emulator
written by master programmer Henrik Gudat, running on a kick-butt
PowerMac, can't match my real 13.75MHz GS in running GS software with
sound off. Turn sound on in the emulator and Bernie slows to a crawl.
Now Henrik one of the most highly skilled programmers I know of, but
you can't escape the fact that an '816 _GS system_ is not as easy to
emulate as your friend claims.
I'll tell you the only way emulation work well. Build a GS around a
PowerPC processor. Port parts of GS/OS to native PPC code, and also
the Toolbox routines, and let a good '816 emulator handle the rest.
Build into the motherboard a modern VGC chip capable of scan line
control and a synthesizer chip capable of wavetable synthesis. That's
how you would get the next generation GS. The processor does not have
to be a 65C816 anymore than the PowerPC in a PowerMac is an 68000.
Like on a PowerMac, the crucial part to speed and bullet proof function
is the porting of the Toolbox to native PPC code. As you must well
know, B.J., a PowerMac is running much of its "Mac" in '040 emulation!
My only conjecture is that if Apple supported the GS, such a RISC chip
as the PowerPC (or, shall I say, PowerGS) would have come from WDC
rather than Motorolla.
>>
>>Additionally, the figure of $100k might be enough to realize the CPU
>>design, but there's no way it will be enough to completely re-engineer
>>the IIgs motherboard - which would be necessary, because the IIgs's
>>memory subsystem wasn't designed for such high bus speeds.
Apple could have and should have done this. The GS outsold the entire
Mac line in its first year. If Apple had done the right thing and
supported the GS, thereby keeping a larger loyal customer base, it
would be in better shape today. And your friend would be saying:
"While the figure of $100k might be enough to realize Motorolla's
68K upgrade design, there's no way it will be enough to
completely re-engineer the Mac Plus motherboard - which
would be necessary, because the Mac Plus' memory subsystem
wasn't designed for such high bus speeds."
>>
>>It would also be necessary to hack (at best... rewrite at worst) the
>>IIgs's firmware, because there are software timing loops in the ROM
>>for things like floppy drive step rate, all of which would be thrown
>>out of whack by a faster CPU.
All this was done when the Mac Plus evolved into modern Macs. If the
inferior Mac Plus design could do it, so can the superior GS design.
Apple simply backed the Mac Plus rather than the GS, a big error that
resulted in loss of market share.
Apple is one of the few companies that deliberately held back the
development of one of its computers (the GS) for fear it would
compete against its favored prodigal child (the Mac Plus and its
evolutions).
>>
>>Sorry, I don't think it's a feasible project. That's not to say it
>>wouldn't be fun, of course.
Of course it won't be feasible today. I think your friend got the
wrong idea. What we in the csa2 community are saying is that Apple,
back in 1987, could have using no more money in R&D did it did working
on the Mac with Motorolla, cooperated with Western Design Center and
developed the GS instead and today we would have a RISC based PowerGS
design plus Apple would be in better shape to boot.
>>=== From the Apple PowerBook of ======================
>>Lewin A.R.W. Edwards [Team OS/2] <http://www.zws.com/>
>>Certified Apple Engineer Programmer
>>Need a programmer? <http://www.zws.com/resume.html>
>>Tel +61-412809805, +61-411499000 Fax +61-392281335
>>=== (C) Copyright 1997 by Lewin A.R.W. Edwards =======
B.J., your friend is part of team OS/2! That's not "Win" but it is
"tel" OS/2 runs on Intel machines. Like I said, there is no such
thing as a Wintel machine. :)
>--bj
>Proud user/owner of Apple Computers since 1984
>Barbie and Ken doll fan since 1961
>Automatic reply will no wo; please reply to bjbear@ibm.net
-Scott G.
Apple IIGS supporter and user. Amiga fan. Fan of both PC and PowerPC,
but not Microsoft (I prefer the PC to run NeXT, Linux, or OS/2).