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Raidmax RX-520XP PSU
Author: jonnyguru
Date Posted:17/03/2005 10:07.18
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Bottom Line:
There's more to picking a PSU than the wattage, as explained in the first of a series of forthcoming PSU reviews.
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Parameters
So what will I be testing?
I will be throwing five
tests at each power supply.
Test number one is the
Zero Load test. This will be performed with no load on the power supply
other than the internal load the power supply provides itself to function,
the load of any fans that may be installed and running in the power supply
and an artificial 5V stand by load of 2A.
The data gathered on this
test will be:
- 12V voltage
- 5V voltage
- 3.3V voltage
- Efficiency
- Power Factor
After this test is performed,
the load tests will begin starting with a synthetic load representative of
three builds
The first build is a a
pretty common representation of a PC found today. Heavier on the 12V
than PC's of the past and lower on the 5V than PC's of the past. We
used a Pentium 4 3.2 Northwood, an AGP video card, 1GB of DDR RAM, two hard
drives, two optical drives and three case fans. For fun, we threw four USB
devices on the machines just to get the 5V load up over 30A.
This is what we came up
with:
- 12V = 19.8
- 5V = 16A
- 3.3V = 3A
So we made our load specs
for this build....
- 12V
= 20A
- 5V
= 20A
- 3.3V
= 3A
This next load test was
based on an Athlon XP 3200+ on a Biostar M7NCD Ultra 400 motherboard, an
AGP card, 512MB of PC2700 RAM, two hard drives, two optical drives and two
case fans.
The estimated maximum load
for the build was:
- 12V = 7.1A
- 5V = 32.4A
- 3.3V = 2.4A
To make worst case scenario
even worse, we made the load specs this:
- 12V
= 10A
- 5V
= 30A
- 3.3V
= 3A
The last build is sort
of gonzo. We built a Pentium 4 3.4E Prescott with two 6800 Ultra PCI
Express video cards, two hard drives, two optical drives, 1GB of RAM, three
case fans and came up with:
- 12V = 31.8A
- 5V = 16A
- 3.3V = 2.4A
When I replaced the Prescott
with an AMD64 3400+, I had enough ceiling to run four hard drives in a RAID-5
array with room to spare. So we decided the load test for this configuration
should be:
- 12V
= 30A
- 5V
= 20A
- 3.3V
= 3A
We also took the power
supply's temperature at this load.
Now, all of these builds
had USB mice and keyboards as well as floppy, NIC... the standard fare. Whether
512MB or 1GB of RAM were used, this was always done by using two sticks of
RAM, which is why the voltage demand never really changed on any of the builds. Naturally,
if you had more sticks of RAM, you'd have more of a load on that rail.
This is what we're looking
for with each of the above four tests:
- 12V voltage
- 5V voltage
- 3.3V voltage
- Efficiency
- Power Factor
That's right. Same
as the Zero load test! I just wanted to make sure you were paying attention.
;-)
We also took a look at
the label and cranked the 12V and 5V up to maximum specs as per the PSU's
label. We then did the math: (3.3+5V Combined Maximum)-(5V * Maximum
Amperage)=(3.3V Testing Amperage Setting) and set the 3.3V accordingly.
At the point where we cranked
up the 5V and 12V to label spec, we were usually already beyond the power
supply's maximum wattage rating, so it wasn't unusual for a power supply's
overload protection to kick in if we tried to compensate a little extra 3.3V. This
is why it ticks me off when a review site says "we ran the power supply
at maximum load" but doesn't break down how the rails were loaded. It's
a given you can't load a power supply to "maximum load" if you
juice up each rail, so one is left wondering where "maximum load" really
is.
This also brings me to
the "power supply blowing up" scenario and what it means to me
and my tests. If overload protection trips, that's good. I actually
rely on overload protection to kick in to effectively test a power supply. If
I run a power supply with a 12V load of 20A and the rail is only rated at
16A and overload protection kicks in, then no big deal. I'm over spec. I
write down that the power supply failed the test and move on to the next
test. This is also how I do the max load test. I set the 12V
and 5V to the maximum on the label and then raise the 3.3V until overload
protection kicks in. When it kicks in, I lower the 3.3V and cycle the
power on the power supply. If the overload protection fails to function,
the power supply blows up. This does not mean that the power supply
is inherently a fire hazard. It means I received a defective unit. Unfortunately,
it also means the testing process comes to a screeching halt.
When everything is said
and done, I lower the load back down to test two and wait for one minute
for the power supply to cool down. We then cut the power off and watch
the Compu-Nurse. After one minute, an idle temperature is taken.
How will the tests be
performed?
I'll be honest... I don't
have three builds I can switch power supplies in and out of. Quite frankly,
I don't have the time to do this that way either!
For testing power supplies,
I am in possession of a SunMoon SM-268, a power supply load tester, and a
little Weibo PF1211, which is a mains efficiency reader similar to a Kill
A Watt, but easier to read because Volts, Amps, Watts and Power Factor are
all displayed on four LED's simultaneously, instead of having to click through
one LCD to get all pertinent information. Despite my wife's best attempts
to convince me to set up elsewhere, the lab is in the dining room.
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