Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!usc!zaphod.mps.ohio-state.edu!uwm.edu!uwvax!jomby.cs.wisc.edu!kolstad
From: kolstad@jomby.cs.wisc.edu (Joel Kolstad)
Newsgroups: comp.sys.cbm
Subject: Re: 4 MhZ 64
Message-ID: <1991Mar5.054117.4796@spool.cs.wisc.edu>
Date: 5 Mar 91 05:41:17 GMT
References: <9103050059.AA15734@cwns9.INS.CWRU.Edu>
Sender: news@spool.cs.wisc.edu (The News)
Organization: U of Wisconsin CS Dept
Lines: 38

In article <9103050059.AA15734@cwns9.INS.CWRU.Edu> ap515@cleveland.Freenet.Edu writes:
>
>
>I've seen this subject of a 4 MHz 64 mentioned in the past.  Can
>anyone give me any information on that?  From what I've heard,
>all you need to do is replace the 6510 with a faster version of
>it.  What is the number of the replacement chip?
>

Ha ha.  Not quite.  Merely speeding up the 6510 and doing nothing else will
merely confuse VIC, SID, the CIAs, and probably other things I've forgotten.

You need to get an accelerator board that has it's own memory and a 4MHz
65C02.  The board has circuitry that interfaces to the "slow" 1MHz bus of
the standard 64. (Whenever you write to I/O memory, it goes over and tells
the "real" 64 about the write.  Otherwise, everything is executing out of
the acclerator's memory and 65C02...)

As far as I know, Schnedler Systems is the only place still selling an 
acclerator board.  Theirs is 1/4MHz switchable, only.  I do recall another
acclerator that had a potentiometer that let you vary the speed from something
like 100KHz to 4MHz, but doubt it's still being produced.

There are a few gotchas: You can't use a 1764 (or any device that uses
DMA) with an accelerator being the biggest.  Also, unless you're into 
heavy cartridge hacking, don't expect an accelerator to let you use your 
favorite "hacker" cartridges (Final Cart, S.S., etc.)  Basically, after you
install an accelerator, your expansion port can only support I/O devices --
data acqusition boards, GeoRAM, Swiftlinks, etc.  (Of course, the
accelerators I know of have disable swtiches for the times you _do_ want
to use the aforementioned stuff...)

Schnedler Systems was at one time considering going into a joint venture with
CMD (the Jiffy DOS folks) to make an acclerator/1764 compatible RAM expansion/
Jiffy DOS board, but these plans apparently fell through.

						---Joel Kolstad
						kolstad@jomby.cs.wisc.edu