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From: toddpw@tybalt.caltech.edu (Todd P. Whitesel)
Newsgroups: comp.sys.apple2
Subject: Re: Mega II (was: Accepting the Mac)
Message-ID: <1990Mar18.095408.1765@spectre.ccsf.caltech.edu>
Date: 18 Mar 90 09:54:08 GMT
References: <1848@crash.cts.com> <18491@boulder.Colorado.EDU> <12667@thorin.cs.unc.edu> <39559@apple.Apple.COM> <1990Mar17.112032.18069@spectre.ccsf.caltech.edu> <12372@smoke.BRL.MIL>
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gwyn@smoke.BRL.MIL (Doug Gwyn) writes:

>In article <1990Mar17.112032.18069@spectre.ccsf.caltech.edu> toddpw@tybalt.caltech.edu (Todd P. Whitesel) writes:
>>The Mega II was not originally designed for the IIGS and its presence is
>>the root cause of many common complaints about the IIGS as a product, ...

>I don't follow the logic.  Certainly compatibility with existing Apple II
>peripherals and software adds substantially to the value of the IIGS, not
>detracts from it.

I never said scrap the II compatibility, I said scrap the Mega II. The Mega II
has to run at 1 Mhz and in the GS that's a big problem. If they had implemented
its functions in a more distributed manner then the only part of the machine
that would run slow would be the actual expansion slots. When the GS was
originally designed they barely had the technological capability to do this,
but for a couple of years now it is has been well within Apple's custom chip
capability.

> Since existing Apple II peripherals were designed to
>work at 1MHz, the IIGS had to slow down when accessing them.

That is true.

> Similar
>comments apply to the weird Apple II graphic modes.

That is NOT true. The video RAM could have easily been made to run fast, but
as they had already developed the Mega II and had to use it for something (I
keep forgetting money wasn't as plentiful back then) it ended up going in
anyway.

In fact, you can implement the Apple II video modes with VRAMs (a la Mac II
video cards) and it is *EASIER* than the new GS video modes. (The explanation
of why this is true is a bit technical about how VRAMs work, so I won't post it
unless a lot of people ask. I'll gladly answer via mail.)

[ random flaming about non-compatibility with the II deleted ]

What I keep trying to convince people is that the II compatibility is cheap and
important but the way it is implemented in the GS positively sucks and could be
done much better, especially now that Apple has more than adequate resources.

That's all I'm saying, nothing about dropping II compatibility which I wouldn't
give up for the world. I'm just saying that the GS needs a totally new chip set
and that without one the GS or its successors will never stand a chance in
today's market.

The custom chip set in the GS implements a logical construct, that of the
memory map and basic operation of the machine. We could scrap them all (not a
bad idea) and make a complete new set that is designed to work together a hell
of a lot better and more cost-efficiently but will still look the same to the
software so compatibility suffers not one whit. With the silicon we'd be saving
we could add more features to make the ToolBox's life easier, and my //f paper
has numerous suggestions as to what can be done in this regard.

Todd Whitesel
toddpw @ tybalt.caltech.edu