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Path: utzoo!utgpu!water!watmath!clyde!rutgers!lll-lcc!ptsfa!ihnp4!upba!eecae!conklin
From: conklin@eecae.UUCP
Newsgroups: comp.sys.atari.8bit
Subject: Re: custom 6502
Message-ID: <2578@eecae.UUCP>
Date: Sat, 12-Sep-87 01:30:42 EDT
Article-I.D.: eecae.2578
Posted: Sat Sep 12 01:30:42 1987
Date-Received: Sun, 13-Sep-87 08:01:09 EDT
Reply-To: conklin@eecae.UUCP (Terry Conklin)
Distribution: world
Organization: Michigan State Univ., Engineering, E. Lansing
Lines: 48
Keywords: 6502 65C02 processing speeds
Summary: Turbo XL in the works



A couple people have found out (somehow?!) already and since
this question was brought up I might as well mention that I
have already been working on the 200% Turbo XL.

The 6502 in the XL ("Sally") is, as was sumarized, a 6502 
with tri-state buffering. When a chip goes tri-state, it 
becomes electronically transparent. Antic tri-states the 6502
so that it doesn't react when Antic starts accessing memory.

The 400/800 (and the TRS-80 for that matter) had tri-state
buffers on the board. To lower the chip count on the XL line,
Atari made a custom 6502 that moves those buffers into the
CPU.

We have long known/required a socket that would simply externalize
those buffers so as to make a path for the XL/XEs take a 
65802/65C02. ActuallyI don't care what you put in it as long
as it's pin compatible and runs 4 Mhz. This socket is indeed
a possibilty, I've just been too busy messing with the rest of
the timing considerations.

Mathematically computed benchmarks of the Turbo XL show it runs
quite favorably with the IBM PC, Mac, and (suprise!) ST. This
was borne out to some extent with the release of the turbo-
upgrade for the C64.

I have no plans for attempting a 16-bit version of the mod.
Granted the 64 mod is, but I am planning this mod to be along
the lines of the 256/320 XL/XE memory upgrades. Something
that many can make, easily. The memory upgrade is great, and
I strongly reccommend it to anyone who does anything other than
play Pacman.

Please dont ask major techincal details, since I'd like to
make a little money from the efforts on this. By no means do
we intend on letting this mod cost more than $50. If it 
gets
that way, then it gets to be PD.

Terry Conklin (and, actually, partner in crime Ken Sumrall)
ihnp4!msudoc!conklin or ARPA: conklin@cps.msu.edu
or we generally carry this discussion on the Club's ATARI
base at (517) 372-3131.
Disclaimer: I bought a Unix machine of my very own. That puts
MIGHTY cross-interests in with this. But if you want results
now, well, get that Kermit65. It's still great!