SUMMARY: Backplane dividers

From: Mark Baranowski (
Date: Wed Sep 19 1990 - 12:40:05 CDT

My original question was as follows:

> I need help in settling a dispute regarding backplane dividers (for
> lack of a better word this is what I am calling the rectangular sheets
> of metal that occupy the empty backplane slots).
> One of my co-workers feels that all backplane dividers should be
> pulled from a system as they are a nuisance. I feel that serious
> damage could occur to the hardware as the backplane dividers are
> essential to proper cooling. To make matters worse, one of the
> customer engineers from Sun told us that the backplane dividers were
> not necessary. Who is right?

11 respondents voted to keep the backplane dividers and 3 voted to yank
them. The biggest reason for keeping them was to increase airflow over
slots having boards and to reduce EMI/RFI emissions.

Here is a sampling of some of the responses:

  The little ledge at the top of the divider reduces the flow of air
  over that particular divider. This increases the flow of air over the
  circuit boards that are installed in the system. BTW, I call them air
  flow controllers.
  System performance can be affected, particularly in older systems with
  less airflow. Random crashes are the usual symptom; Furthermore, IC's
  age much more rapidly at higher temp (>40 deg C or 100 F) than they do
  at lower temperature (<30 deg C or 85 deg F), thus hardware
  depreciation is affected and cost of maintenance is affected.
  I believe that there is some protection from inter-board interference
  with a metal "divider" between the boards. Also, the "dividers"
  will help the chassis and board guide rails maintain their shape in
  case of stress.
  We run our 3/[12]60s with and without these dividers and have
  experienced no difference in the amount of failures the systems
  experience (hardly any in either case). I usually try to keep the
  dividers in as I don't want to throw them away, and the card cage is a
  good place to store them.
  Hmmm, it's more like "you can get away without them..." but it really
  depends on your environment and what you have in the box. High
  ambient temps and/or something in the box that is temperature
  sensitive and you'll see problems. I have two systems here - one
  won't run without them, and the other runs fine, but all it has is a
  CPU and a memory board, I'm constantly swapping boards in and out.
  Bottom line - Sun wouldn't ship all that metal if it didn't do
  When the system becomes obsolete it will make a much better boat
  anchor with them in.

Thanks to all who responded:
  lsf@astrosun.TN.CORNELL.EDU (Sam Finn)
  "Anthony A. Datri" <convex!>
  Emmett Hogan <>
  auspex!brogers@uunet.UU.NET (Bob Rogers) (Frank P. Bresz)
  sid@Think.COM (Phil Hammar) (Lee Vrieze)
  cook@stout.atd.ucar.EDU (Forrest Cook)
  kevin@Corp.Sun.COM (Kevin Sheehan {Consulting Poster Child})
  dws@Corp.Sun.COM (Dennis Sexton)
  Jeff Nieusma <nieusma@eclipse.Colorado.EDU> (Daryl Crandall)

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