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From: toddpw@tybalt.caltech.edu (Todd P. Whitesel)
Newsgroups: comp.sys.apple2
Subject: Re: Apple II... OLD?!?
Message-ID: <1990May9.223155.5705@laguna.ccsf.caltech.edu>
Date: 9 May 90 22:31:55 GMT
References: <9005091437.AA18970@apple.com>
Sender: news@laguna.ccsf.caltech.edu
Organization: California Institute of Technology
Lines: 50

whitewolf@gnh-starport.cts.com (Tae Song) writes:

> The 65816 is extremely poorly designed in many ways.

depends on your point of view, really.

>It only has 3 registers, lacks lot of logic circuits to shave cycles on many of
>the instructions.  Has trouble running at high speeds.

3 registers: that's what direct page is for. There aren't a lot of internal
registers, but the 65xxx can get at direct page and stack very fast. Since
these often fit entirely in the data cache the higher clock speeds largely
offset the lack of registers.

Lack of cycle shaving: this is something Mensch would love to fix but until
someone rich wants him to build the 65x32 he is not about to risk the money.

Trouble at high speeds: I maintain that this is due to Mensch's "kitchen table"
mask. I am fairly convinced that economics is what prevents him from fixing it.

>The GS design isn't so hot either... somewhere the GS engineering must've
>gotten confused.  The GS can be expanded to 8M, but only 4 of those are DMA
>compatible.  They must've thought of limiting to 4M like on the Macs... we
>(Apple) won't want a computer that can hold more memory than a Mac would we
>(Marketing).  Almost every I/O operations must be bottlenecked to 1Mhz,
>including/during DMA accesses and even to built-in peripherals and video.

All true. And all so easy to fix.

>2.5 is a small# in any case... and if ASIC pulls through with the 20+Mhz 65816,
>I can't see WHY Apple couldn't make a killer machine.  Even at 2.5Mhz the GS
>puts in a good show... 20Mhz is 8x faster... if Apple let's the engineers wring
>all the speed out with caches, DMAs, etc... I think seriously it would give
>EVERY machine a run for their money.

My point exactly. The "Apple //f" paper I wrote proposes one such machine.
Apple already has most of the technology, they just need to be willing to put
it into the new design.

> The GS is running at all of 2.5Mhz!!!  It only takes two intelligent people
>to push that # up to maybe 20-25Mhz... then you'd better watch out!

It took two people to design and lay out the 65816.
It's taken two others with industry connections to reimplement it with state of
the art technology.

It's about time the Apple // kicked some butt for a change.

Todd Whitesel
toddpw @ tybalt.caltech.edu