Subject: Re: UltraDMA performance.
To: dkwok <dkwok@iware.com.au>
From: Wolfgang Rupprecht <wolfgang@wsrcc.com>
List: port-i386
Date: 01/06/2001 13:37:02
dkwok writes:
> Power supply..Hmm, how does it affect the performance?

Some of the newer CPU's (Athlons and P4's) really suck down the power.
(Worst case is 80watts for just the Athlon CPU itself.)  If the +12v,
+5v or +3.3v supplies can't supply the current needed you'll see
intermittent problems whenever something tries to use a bit of extra
current from the weak rail.  For example, things such as a disk-arm
seek or a disk spinning up would cause a bit more of a load on the
+12.  I had a problem where my board (running -current) locked up once
when I did an "ls -lag /u/src" (a directory with a few hundred source
trees.)  I suspected a +12v problem, and knew the Antec 300w supply
was a bit on the weak side for an Athlon, so I replaced it.

Note, you can't really judge a power supply by the total wattage
rating.  You really have to compare each of the "rails" to the needs
of the system.  Digging up the current demands of everything can be
challenging.  Intel motherboards come with pretty good docs.  The IBM
drives come with idle and spin-up current specs.  Some of the other
manufacturers aren't quite as good at documenting their boards.

-wolfgang