[Beowulf] ammonite

Jack Wathey wathey at salk.edu
Mon Oct 4 16:37:15 PDT 2004

On Mon, 4 Oct 2004, Jim Lux wrote:

> At 03:19 PM 10/4/2004 -0700, Jack Wathey wrote:
>> http://jessen.ch/ammonite/
> Very nice.. particularly the efforts you put into the cooling air. The 
> comment about flow against a pressure drop is very sound.
> I realize it's a time thing, but had you considered removing the fans from 
> the power supplies?

The linear flow rate through the whole rack is typically about 120 to 200 
fpm, which is sigificantly less than the linear flow rate through a PS. 
If the PS fan was there *only* to cool the mid-tower box it was meant to 
go into, then removing it would do no harm.  But a PS generates a fair 
amount of heat of its own, so I left the fans.  And as you say, it would 
have taken time.

> What's a rough order of magnitude cost on the blower/VFD?  Does this VFD have 
> a "servo" input that could be used to automatically change blower speed in 
> response to temperature?  (some VFDs have an analog input that can be used to 
> set up a speed = linear function of input voltage, and by cleverly setting 
> the gain and offset, you can do quite nicely)

The blower was about $1300, the Teco inverter about $1000.  The inverter 
has an rs232 interface for computer control, which I don't use at present, 
but hope to some day.  It also has the analog control feature you 

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