Path: utzoo!mnetor!uunet!husc6!uwvax!astroatc!johne
From: johne@astroatc.UUCP (Jonathan Eckrich)
Newsgroups: sci.electronics
Subject: Re: Wire-wrap Question
Message-ID: <714@astroatc.UUCP>
Date: 15 Jan 88 22:26:56 GMT
References: <7110004@hpcupt1.HP.COM>
Organization: Astronautics Technology Cntr, Madison, WI
Lines: 29

In article <7110004@hpcupt1.HP.COM> glowell@hpcupt1.HP.COM (Gary Lowell) writes:

>
>Does anybody know if wire-wrap can be used to build a reliable proto-type
>at 20 Mhz clock rates and what techniques can be employed minimize
>problems ?  I am trying to determine the feasibility building a homebrew
>computer using 20 Mhz 80386 chipset.
>

Much to my surprise, I learned from some fellow engineers here that wire wrap
is actually *more* reliable than say copper clad-type pc boards.  We have wired
wrapped a few prototype boards that used 22.5 Mhz clocks.  

To improve reliablity, make sure you use at least one bypass capacitor per
every two chips.  Place them as close to the chips as possible.  For the
proto board, use somthing that has copper or tin on one or both sides.
You then use a cyldrical-like scrapping tool to remove just enough of the
metal around each hole that you plan on having a component's pin inserted.
The main thing to remember is that higher frequency circuits generate more
noise, and are more suseptable to noise, so use those bypass caps, and
employ GOOD grounding and shielding techniques.  Try to keep the lengths
of the wires short, and keep the design as "clean" as possible.


-- 
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Jonathan Eckrich                 |   (rutgers, ames)!uwvax!astroatc!johne 
Astronautics Technology Center   |   ihnp4!nicmad!astroatc!johne
Madison, WI                      |   (608) 221-9001