Path: utzoo!utgpu!utstat!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!hplabs!hp-pcd!hplsla!tomb
From: tomb@hplsla.HP.COM (Tom Bruhns)
Newsgroups: comp.sys.amiga
Subject: Re: A1000 Bus Noise / Power Consumption
Message-ID: <5160026@hplsla.HP.COM>
Date: 27 Feb 89 16:53:00 GMT
References: <14999@cup.portal.com>
Organization: HP Lake Stevens, WA
Lines: 47

>
>I recently purchased a used CLtd SCSI controller and hard drive for my
>Amiga 1000. I also have a StarBoard 2 with 2M. 
>
>Whenever I have both the StarBoard and the controller installed, my
>system crashes frequently (every few minutes). The controller without the
>StarBoard, or the StarBoard without the controller, seems to work OK.
>When I got my Starboard a year or two ago, I had to ground the chips
>on my daughterboard to reduce bus noise and keep the system from crashing.
>I think that with the additional device on the expansion bus, I need to
>do something more. I have three questions:
>
>  1) There is some other modification I have heard of somewhere, which
>     (I think) involves putting filter capacitors on the power lines 
>     of the expansion bus to further reduce bus noise. Does anyone know
>     the specifics? What size capacitors, connected how? I am not very
>     comfortable making hardware changes without very specific
>     instructions.
Brad Fowles, I believe, posted something a month or so ago which he said
came from Microbotics, concerning a bus terminator.  It consists of a
three-component network, replicated 20 times.  Each network is: 4.7K ohm
resistor to +5, and 1K ohm resistor in series with .001 microfarad capacitor
to ground.  The networks go on each data line, and UDS, LDS, R/W, and AS.
These are pins 63, 65, 67-72, 74-84, and 86 on the expansion connector.
You can pick up ground on pins 1, 2, 3, 4, 13, 25, 37, 49, 61, 73 and 85,
and +5 is on 5 and 6.  It's easy to build the terminator on an 86-pin
edge connector (socket) that just plugs onto the end of the bus, provided
all (both) you expansion devices have pass-through.  See below for my own
testimonial...
>
>  2) Is it possible that instead of bus noise, power consumption is my
>     problem? The controller pull 450 ma. I don't know how much the
>     StarBoard pulls.
>
>  3) Does anyone out there in net-land have both a StarBoard 2 and a 
>     CLtd controller working on an A1000?
I don't, personally, but I had the same problem getting two StarBoard 2's
working at the same time.  And adding the bus terminator made it all
work just fine.
>
>Thanks for any help and advice you can give me.
>
>Bruce Bowers
>----------
You are welcome.
Tom Bruhns
tomb%hplsla@hplabs.hp.com