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From: mikes@iuvax.cs.indiana.edu (Michael Squires)
Newsgroups: comp.sys.tandy
Subject: Re: Tandy 4000/LX
Keywords: CPU Speed.
Message-ID: <1991Feb10.225440.26401@news.cs.indiana.edu>
Date: 11 Feb 91 03:54:33 GMT
References: <1991Feb10.065907.311@ttank.ttank.com>
Distribution: usa
Organization: Computer Science, Indiana University, Bloomington.
Lines: 28

In article <1991Feb10.065907.311@ttank.ttank.com> karl@ttank.com writes:
>big question (I haven't been inside I Tandy 4000/LX for a while now)
>I think the LX had a removable set of crystals.  Would it be worth a
>try to order 25Mhz crystals from National Parts and plug them in?

The 4000/4000LX had memory problems at 16/20MHz; there was a service
mod that tied pull-down resistors onto the back of the board to keep
the ringing from causing memory errors.  I would suspect that even
if the other chips ran at 25MHz that the board would not be reliable.

386/25 motherboards are down in the $600-800 range so I would not think
that this was a good idea.  In my case I purchased an AMI 386/20 motherboard
with cache which runs about 20% faster than the 4000LX and moved the cards
over from it.

>While I am at it anyone know of a way to upgrade a Tandy 4000 or
>4000/LX to a 486 cpu?

Only by buying a 486 board and plugging it in; BSI was selling a new
board with 0K for $1500 or so (486/25).  If you run only DOS the speed
differences between a 386 and a 486 may not be worth it; my 486/25 clocks
at 12,000 Dhrystones under DOS, 21,000 under UNIX; 4000LX runs about 5500
and the 386/20 cache at 7500.
-- 

Mike Squires (mikes@iuvax.cs.indiana.edu)     812 855 3974 (w) 812 333 6564 (h)
mikes@iuvax.cs.indiana.edu          546 N Park Ridge Rd., Bloomington, IN 47408
Under construction: mikes@sir-alan.cica.indiana.edu