FW: [Malvern] PC PSUs

[Ian Pascoe]

Steve and chris - thanks!

When a PC starts up does everything get powered up at the same time, or is
it done sequentially ?  If the latter what governs the start up regieme?

However, from what you both have said, I presume it is the former, and that
PC designers expect the PSU to be able to cope with any peak demands on
startup.

Apart from cost, is there any reason why each component couldn't have it's
own tailored PSU?  (I'mn thinking here of the benefits given to high end
audio systems where each individual component in something like a CD player
has it's own regulated power supply)
Ian

-----Original Message-----
From: malvern-bounces at mailman.lug.org.uk
[mailto:malvern-bounces at mailman.lug.org.uk]On Behalf Of Chris Eilbeck
Sent: 07 February 2007 22:45
To: malvern at mailman.lug.org.uk
Subject: Re: [Malvern] PC PSUs


On Wed, Feb 07, 2007 at 09:41:00PM -0000, Ian Pascoe wrote:
> Hi All
>
> Why are PC PSUs so highly rated ie 400+ watts?
>
> I know that the CPU and Graphics card gets rather hot so must take some of
> the power, and of course you have the power for the hard and optical
> drives, but even so this still seems a high wattage compared to what there
> is inside a normal PC these days.
>
> My only thought on this is that they have to spec up what the power drain
> would be if all PCI slots were used, all USB devices were powered from the
> PC etc etc - am I on the right track here?

Graphics cards are the big killer these days but the main processor sucks a
fair whack too.  A modern hard drive will take 30-40W on startup, 15W
operating.  A USB device cannot suck more than 2.5W from the bus (500mA at
5V).

It's worth noting too that switching power supplies are inefficient and the
voltage regulation is poor if they are run much less than their rating i.e.
you'll only achieve the spec if they're 90-100% or rated load, at 10-15%
say, they'll be out of spec and there's a good chance of blowing components
because of the voltage rails being high compared to what they should be.
Sucking 100W from a 500-600W supply is bad, mmkay?

Chris
--
Chris Eilbeck
MARS Flight Crew                              http://www.mars.org.uk/
UKRA #1108 Level 2                                                UYB
Tripoli UK Member #9527                                          LSMR

_______________________________________________
Malvern mailing list
Malvern at mailman.lug.org.uk
https://mailman.lug.org.uk/mailman/listinfo/malvern