Date: Mon, 7 May 2001 17:37:01 -0600 (MDT) From: Doug Russell <drussell@saturn-tech.com> To: "Chad R. Larson" <chad@DCFinc.com> Cc: Eric Jacoboni <jaco@teaser.fr>, freebsd-stable@FreeBSD.ORG Subject: Re: Lockups with -Stable on Athlon Message-ID: <Pine.BSF.4.21.0105071715010.99490-100000@beastie.saturn-tech.com> In-Reply-To: <200105072124.OAA00573@freeway.dcfinc.com>
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On Mon, 7 May 2001, Chad R. Larson wrote: > > Jonathan> Yes, that's what seems strange. My heatsink is quite large > > Jonathan> and feels cool to touch. I'm wondering if my PSU is being > > Jonathan> overstretched since it's 250W > > > > Mine is 300W. But i think the whole box will power out, not freeze, if > > it was a power problem. > > Not necessarily. > > When a switching power supply gets over (or near) its limit, it > starts generating ripple in the DC power lines. It doesn't shut > down unless it has overload protection built in, and even then only > if the overload is significant (like, 20%). Yes. The overload protection in most supplies is just short circuit protection, and/or catastrophic failure protection for your MOBO. I've seen many fried motherboards from cheap supplies who catastrophically failed, but the catastrophic failure protection failed catastrophically! :) I've seens some supplies put out a nice flat DC line to well above their rated output, but introduce occasional nasty spikey noise or nasty drops. The noisy DC, and/or quick voltage drops, are both easily responsible for these types of crashing problems. The M/B doesn't have THAT much storage capactitance on it.... One other thing I neglected to mention before, is that all supplies of a given wattage rating are not even attempting to all be equal in the first place. Back in the day of 5.25" hard disks, you needed lots and lots of 12 volt. An old-school 230 Watt AT power supply likely was rated to put out about 23A of +5 (115W), 10-12A +12 (120-144W), the reset negative. I've seen ATX 150W supplies RATED everything from about 10A +5/3.3, with about 8A of +12 supply, to 18A on the +5v, and only 4A on the +12. This is why AMD states something like "OEMS might use a smaller power supply as they have tighter control over the individual components." Most modern machines with a single hard disk drawing perhaps .4A of +5, and .25A of +12, a CD-ROM, motherboard, etc, doesn't need a supply capable of 100 watts of 12 volt supply. Good luck when you want to install a burner or something, though. I think this practice of putting just barely-adequate supplies in machines is terrible. Current 250W and 300W supplies vary significantly. I've seen many supposedly 300W supplies that are only rated at 20-22A on the +5, others at 30A. Also watch the total power allowed on the combined +3.3/+5. I've seen (and laughed at) supplies that are rated 30A on the +5, but then say "total power of the 3.3 and 5 must not be greater than 120 Watts". Uhh... didn't you just say you could put out 150W of +5 ??? I'd have to test one of those to see if it was a typo (possible), or really poor engineering. :) Quality hardwarte, folks. Quality hardware. It doesn't have to cost a fortune, you just have to find the parts with the most 'bang for the buck.' That's what I do every day. Later...... <Doug> To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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