Hi Tyrenta and wharf rat,
Apologies, but I have made a mistake in my calculations. For average
components, the total should be 475.5W with an 805W supply. Obviously the
figures of the PSU seem large, but bear in mind that I am adding 10% to the
power consumption figure and assuming a PSU efficiency of 65% and that you
want room for expanding your system. Another reason for such a seemingly high
rated PSU is for operational stability - glitches on the mains supply caused
by other equipment in your house can cause systems to reboot for no apparent
reason other than the output on the 'power good' line to fall momentarily
below the threshold, a phenomenon known as 'brownout'. Even if your machine
stays on and doesn't reboot, this fluctuation in power can cause data
corruption and loss. This is particularly prevalent under high load
conditions, especially where the PSU has insufficient reserve capacity. Bear
in mind that the rating quoted for a PSU is the total theoretical output and
that the rating for an individual power rail will be lower. If you exceed the
power rating for a power rail, then you are likely to encounter problems,
even if the total PSU wattage available is ample for your system. It is
important when thinking about upgrading your PSU to consider not only the
total power requirement in your system (and to factor in some level of
redundancy), but also the specific power requirements for the different power
rails. This is especially true of the 12V rail since it is that rail that
supplies the power for all the drive and fan motors in the system. A lot of
PSUs seem to come with a whole multitude of outlets and some people make the
mistake of assuming they can have a device on each outlet. This is a mistake,
as all but the highest quality (and priced) PSU will not be able to cope with
such a load. In general, I recommend no more than 2 devices per supply line
(for hard disks) or 3 (for optical and floppy drives). Case fans should be on
their own line, but if you do need to use a power splitter then split the
supply to the optical/floppy drives rather than the hard drives because an
optical/floppy drive is only used ocassionally whereas a hard drive is in
constant use.
Dwarf
"Tyrenta" wrote:
Quote:
> On Mar 13, 8:37 am, w...@xxxxxx (the wharf rat) wrote: Quote:
> > In article <DF44A77E-A389-4A6F-A798-D2BD970D6...@xxxxxx>,
> >
> > Dwarf <Dw...@xxxxxx> wrote:
> > Quote:
> > >If you are using average rated components, I recommend a supply of 650W.
> >
> > Well, that's just silly. There must be something wrong with your
> > figures because even a decent 380 watt PS is perfectly adequate for an
> > ordinary desktop system.
> >
> > For instance, I make an 80mm case fan to be 12v x .15a = 1.8 watts.
> > Are you figuring startup current as your steady state? That would only
> > apply to motor driven parts like fans and drives. That's momentary and
> > the other components aren't drawing anywhere near peak when it happens.
> > And what x86 CPU uses 150 watts? Max current for an AMD X2 is 89. Some
> > of the Intel quads get as high as 130...
> > Quote:
> > >Motherboard 50W 75W 62.5W 15w
> > >Processor 25W 150W 87.5W 90w
> > >RAM 10W 30W 20.0W 6w
> > >Graphics 25W 200W 112.5W 60w
> > >Hard Disk 90W 180W 135.0W 14w
> > >Optical 30W 70W 50.0W 30w
> > >Cooling Fan 6W 10W 8.0W 1.8wx3=5.4w
> >
> > My figures are closer to 250 peak 180 steady state... So a
> > 300-350w power supply should be fine for normal usage... >
> Thank you both -- I think the problem (or dumb move) was trying to
> replace a 2-disk data (non-OS) RAID with a 3-disk RAID, so to
> transition I actually had 7 (5 RAID + OS + a back-up IDE) drives
> running, but ideally that would drop back to 4 or 5 when I'm done. The
> largest supply I could get locally (Circuit City) is a 500W, so I'm
> hoping that would be sufficient, and I could try to disable a few
> components (the IDE, and possibly the optical) while building the
> RAID.
>
> the rest of the system is fairly standard by todays compents -- AMD
> 3800+, 3gb RAM, middle line video card, 1 optical drive, 2 case fans
>
> could a low power state have caused the software issues (inability to
> lauch several components), or likely I need to do a complete reinstall?
>