dsads said:
This means that if the 12 V rail is showing a 12.5 V then it is
actually too much power there.
On the 3V &5 V rails I've noticed around 2.8V & 4.7V respectively.
Is this fine?
2.8V is 15% low, 4.7% is 6% low, and the ATX standard allows a
tolerance of +-5%, but 12.5V is only 4% high and within tolerance.
But I wouldn't have any confidence in those measurements because if
the +3.3V really was 15% low, the computer would probably not work
well at all, and motherboard voltage measurement hardware is so
notorious for inaccuracy that any abnormal readings must be verified
with a digital voltage meter.
I believe your Asus a7v8x motherboard consumes most of its power form
the +5V, making the supply's combined power capacity, the measure of
the maximum power available from the +3.3V and +5V simultaneously, an
important factor, and a 2.8 GHz system may need as much as 180W of
such combined power. If your motherboard doesn't have a 4-pin power
connector, either a square one (ATX12V) or rectangular (disk drive
power connector), then its +12V amp capacity doesn't have to be very
high, even if several disk drives have to be powered. On the other
hand, a motherboard that does have such a conector may drain as much
as 10A from the +12V, and the power supply for it should be capable of
putting out at least 15A, maybe 17A if at least 4 disk drives will be
used. But such a motherboard won't need a high combined power capacity
at all.
Most 300-350W and larger power supplies are rated to provide at least
180W combined power, but unfortunately manufacturers' ratings vary
widely in truthfulness. Nor can you rely upon reviewer because the
vast majority of them are done incompetently and consist of little
more than measurements of the voltages with nothing but a computer to
serve as the load (of only 200W, ridiculous when the power supply is
rated for 500W). Most reviewers simply don't have the know-how or
resources to run proper tests, but even Anandtech, a relatively
affluent web site, is guilty of publishing some of the worst power
supply reviews. Some of the few web sites that have done halfway
decent testing are
www.tomshardware.com,
www.silentpcreview.com
(detailed explanation of testing),
www.nordichardware.com, and, in the
past,
www.tweaktown.com (they used to test to 110% of rated maximums,
but now they're as bad as anyone else), and maybe
www.computerbase.de
(I don't read German). Any review that doesn't include amp
measurements should be ignored.
The best choices in power supplies are probably FSP (Fortron, Source,
Powerman, Sparkle, Aopen, Hi-Q, Trend), Antec Truepower (Smartpower
and Solution Series are good but a notch below), PC Power & Cooling,
HEC (Heroichi, Compucase), Channel Well Technology (Leadpower)
CWT-ppp-Axx series (same as Truepower; CWT-ppp-Bxx are Smartpower or
Solution Series; others apparently are quite a bit worse), and hard to
find brands sold primarily to large OEMs, such as Astec, Zippy-Emacs,
Win-tact (these 2 and FSP make the cores of PC Power & Cooling's
products), Lite-On, NMB, Newton, and Delta (Acer). Many of the
ultra-quiet power supplies are modified FSP designs.
Some second-rate but perfectly good power suppies include Sirtec
(Vantec, Thermaltake, Highpower, and some others), Enermax
(Wavesonic), Enlight, and Enhance (Freeway).
Brands to avoid include Leadman (Powmax, Raidmax, Robanton), although
it's actually the best of this group, Q-tec (not to be confused with
Q-Technology, which are high quality products based on FSP products),
and any of the numerous Deer brands, such as Eagle, Mustang, Hyena,
Foxconn, Foxlink, Codegen, L&C, Austin, Allied, Powerstar, Logic,
Duro, and maybe Mercury. Any power supply selling for an unusually
low price can't be trusted with your computer and data, unless it's an
odd surplus product. Also avoid brands sold mostly for their
decorative features (aluminum case, lighted fans, braided cables) or
that have more than 2 fans (extra fans are mostly decorative, not good
design).
In most cases there's no need to spend more than about $40 for a top
quality power supply, such as a Fortron or Sparkle from Newegg.com or
Directron.com, but for less than $75 they have 500W models that can
run anything.
