peter said:
If you go to the AMD website and look at the PC Builder specs for fan
location and air circulation in any case,you will note that they suggest a
front low blow in case fan .This fan blows in cooler air whereas the rear
mounted fans should be placed higher(hot air rises)to expell the hot air.The
side cover fan usually is located in such a manner that it blows cool
outside air over the PCI cards or towards the CPU cooler.If it is on the
opposite side of the MOBO then it would be set up to draw the air out.
peter
Note also that if all of your fans are blowing *out* and the
only air intake if what leaks in through the case, then you
reduce the air pressure inside the case. The lower air
pressure means a lower air density - and the ability of the
air to remove heat from your heatsinks should be proportional
to the density.
I have seen computer cases where all of fans are blowing
outward and there are no big vents to let air flow into
the case: plastic side panels on a case can bulge inward
very noticeably when the system is powered up - which clearly
indicates a reduction of air pressure inside the case.
Even on steel cases you can detect side panel concavity by
taping small mirrors to the panels and noting the changes
in the angle at which the beam from a laser pointer is
reflected.
Turning even just one fan around so that it blows inward can
give you a dramatic temperature reduction and a noticeable
noise reduction.
On a system with a PSU fan and three case fans I have found
that I get the best temperatures when two case fans blow
inward and only the highest case fan blows outward. When
there is only one case fan, I always get the best temperatures
when the case fan blows inward and only the PSU fan blows outward.
When there are two case fans it is not so clear - sometimes it
works best when the lowest one blow in and the highest one blows
out, but other times it works best if both blow in and only the
PSU fan blows out.
My tests were all pretty crude - just three mid-tower cases and
one full tower case all with three case fans each. I simulated
one and two fan configurations by unplugging fans and using pieces
of duct tape over the grills to seal off the openings. Its been
a year and a half since then and CPUs and video cards have
gotten a *lot* hotter in the meantime - I would love to see
up to date results if someone does some tests with modern
hardware. I also did not have tools to measure air pressures
inside the case - I would have loved to be able to see various
air pressure vs temperature graphs.