Hard drives and inrush (was < 3 SCSI Drives on ISC 2.02)

[John G. DeArmond]

src at scuzzy.mbx.sub.org (Heiko Blume) writes:

>the danger is how much the drives need when you power them up. i RTFM'ed
>a bit and found out that my 600MB WREN V uses up to 4.5 ampere on startup
>(on 12V). well, most 220 watt power supplies can give you 8 ampere on 12V
>so if you connect two of these beast you might get problems.
>i also phoned around, and bigger power supplies like 300+ watts are very rare
>and *very* expensive. i'll get more info next week, anybody interested?


It might also be helpful to note that most large SCSI drives have an option
to stage spindle spinup according to each drive's  SCSI address.  For 
example, on both my Newbury and my Maxtor drives, setting a jumper causes
the spindle to delay spinup according to the formula: 

delay = (13 sec * SCSI_ID)

This should solve any power supply inrush overloading.

John

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