"Hank" said in news:
[email protected]:
SAY WHAT?? What you been smokin?
Muttly, mount the friggin PSU like its supposed to be with the fan
pointed down. It aint nuclear science like some would like to make
you believe.
Hank
It all depends on which ATX specification the power supply follows. In ATX
pre-2.2 power supplies, the air flow was INTO the case at the rear panel so
air flow was INTO the power supply's opening on the backside of the case;
i.e., the power supply's rear opening was an air inlet. This contradicted
the earlier AT spec which had air flow move out of the case as an exhaust
port. ATX 2.2 reversed the air flow and now, like the AT spec, has airflow
move OUT of the power supply at the rear panel. So for the power supply
opening at the rear of the case:
- For an AT power supply, air flow is OUT of the case.
- For an ATX pre-2.2 power supply, preferred air flow is INTO the case.
- For an ATX 2.2 power supply, preferred air flow is OUT of the case.
ATX 2.01 Specification (released 1996), Section 4
ftp://download.intel.com/design/motherbd/atx_201.pdf
ATX 2.03 Specification (released 1997), Section 4
http://ulita.ms.mff.cuni.cz/pub/techdoc/atx/atx2_03.pdf
"The 'preferred' airflow solution is to pull air through the power supply
from outside the chassis and direct it onto the processor. However, other
solutions may be implemented to meet the specific cooling requirements."
ATX 2.1 Specification
http://www.formfactors.org/developer\specs\atx2_1.pdf
This spec doesn't say anything about airflow direction for the power supply.
There is the implication that airflow is the same as in the prior specs per
Section 5.1, "Venting", where it says, "Adequate venting should be provided
in the system to allow for unimpeded and well-designed airflow to cool key
components such as the processor." But airflow in either direction across
the processor would assist removal of the warmed air from the processor
(although a PSU that exhausts air across the processor may be doing so with
pre-warmed air taken into the PSU through its internal-side vents).
ATX12V 2.2 Specification, Section 4.3
http://www.formfactors.org/developer/specs/ATX12V PSDG2.0 Ratified.pdf
"In general, exhausting air from the system chassis enclosure via a power
supply fan at the rear panel is the preferred, most common, and most widely
applicable system-level airflow solution."
The ATX specification as regards to the direction of airflow through the
power supply are only recommendations (i.e., they are ambiguous). As such,
you have to test your power supply to see which direction is its airflow. I
picked up a Fortron 350W PSU about 2 months ago which has 2 fans. The
bottom fan is an inlet port (air goes INTO the power supply) and the rear
fan is an exhaust port (air goes OUT of the power supply). So my power
supply is ATX12V 2.2 compliant, and the fans work in concert to pass air
*through* the power supply instead of working against each other. The
bottom fan is primarily a backup in case the rear fan stops spinning or
spins too slowly (especially for rear fans with manual speed adjust).
Sometimes the rear fan is temperature controlled but the bottom fan is
usually fixed speed (because it is the backup or to ensure a minimal flow
rate).
2 equally strong guys push against opposite sides of a crate. The crate
doesn't move. The same 2 equally strong guys pull against opposite sides of
a crate. The crate still doesn't move. 2 guys of different strengths push
against opposite sides of a crate. The crate moves slowly in the direction
of the weaker guy. 2 guys of different strengths pull against opposite
sides of a crate. The crate move slowly in the direction of the stronger
guy. 2 guys of equal or unequal strength either both push or pull against
the crate in the same direction. The crate moves fastest in that direction
because the guys work together instead of opposing each other. Fans provide
the force. Air has mass and momentum, too. Hank never took physics in high
school, or he failed, or he skipped that class or high school altogether.
If the ATX power supply has the *optional* cooling vents on the inside
(where the wire harness exits), the fans could both be pushing air out of
the power supply; i.e., the rear fan would exhaust out of the case and the
bottom fan would exhaust out across the processor. That is because you now
have an alternate path for airflow other than through the openings for the
fans. However, realize that the vent openings on the internal side of the
power supply are rarely sufficient in their cumulative size to accomodate
the same [potential] airflow provided by just one of the fans. Also realize
that the bottom fan would then be recirculating the pre-warmed air from
inside the case across the processor. So despite if there are vents or not,
you want to either move the cold air in or the warmed out. You don't want
to be sucking the air that has already been warmed by the hard drives,
expansion cards, RAM sticks, and processor into the power supply's inlet
vents to only then get recirculate that pre-warmed air back over the
processor.
Your CPU probably has its own fan. Figure out which way the rear fan in the
power supply is directing airflow, then make the bottom fan on the power
supply move the air in the same direction so it assists with airflow rather
than opposes it.
