"Gwen said:
I've been working on getting my game/pvr box tweaked, and I think I'm
down to the wire for the last few questions.
I'm finding (according to my monitoring software, that the CPU heats up
into the yellow band on the temperature gauge (I'm not home to check
the exact number). The interior of the case tends to be about 10*C
cooler, nicely in the green where I want it to be.
I'm going to take a WAG and assume this means I need a better fan for
my CPU, but, the general interior of the case is fine as far as temp.
I have an AMD Athlon 64 X2 3800+ Socket AM2 processor. What third-party
fans would be recommended for it?
Actual temperature readings are better.
Say the room air temp is 25C. A well cooled computer case will have
an air temperature of 32C to 35C or so. Such a temperature is desirable,
since the disk drives are the most sensitive part when it comes to
heat, and low temps like that make it easier to keep the disk drives
within spec. The curve for disk drives takes both humidity and
temperature into account, and at 60% room humidity (where carpets
begin to mildew), a disk drive is rated for a surprisingly low
temperature.
The inside case temperature affects the ability of the CPU cooler to
do its job. A CPU cooler "adds" its temperature, to the case
air temperature. If the CPU cooler in a particular situation
adds 20C to case ambient, then you'd see 52C to 55C as the
CPU temperature, for the well cooled case suggested above.
As the case temp goes up, so does the CPU.
Heatsink performance is rated by theta_R or thermal resistance.
A good heatsink might be 0.2 degrees C per watt or less. If
the processor was 90 watts, the temperature rise of the CPU
cooler would be 18 degrees C. And that is added to the case
ambient, leading to 50C to 53C CPU temperature in a well cooled
case.
So an aftermarket heatsink with a good theta_R can help.
But you also have to consider other sources of heat in the
case, and whether you (or the manufacturer) have done a
good job of mitigating cooling issues. For example, if
I take my favorite video card, and put an Arctic Cooling
VGA cooler on the card, a cooler like that uses an adjacent
PCI slot cover, as a place to dump exhaust air. With that
kind of cooling solution for the video card, the video card
exhaust leaves the case immediately, instead of recirculating
inside the case.
Looking at your case, there seems to be a provision for a
duct above the processor. This will only work effectively,
if the motherboard places the CPU socket in just the right
position, the CPU heatsink assembly is just the right height,
so that the duct mates with the top of the cooler. A duct
allows unheated room air to be fed to the CPU cooler, which
at least helps the CPU temperature. But if the exhaust leaving
the CPU cooler is not directed somewhere, then a "warm cloud"
develops around the processor area.
That leaves the computer case exhaust fans. Their job is to
evacuate the hot air from the CPU area, and establish a
preferred airflow direction in the case. Generally, you want
cool room air entering near the disk drives. That does the best
job at keeping the disk drives cool. Next the air passes the
CPU area, and carries away the "warm cloud". And finally the
video card (if equipped with a slot output), rear exhaust fans,
and PSU fan, help move the air out the back of the computer case.
Now, violations of those rules, can prevent even the nicest
cooler from helping you. I had a Zalman 7000 series on a
motherboard, and it didn't seem to be doing that much for
me, even though its theta_R is around 0.20. I ended up opening
additional ventilation space on the front of the computer, so
that the 120mm exhaust fan on the back of the computer could
do its work. If you hear the fan speed change when you lift
the lid (or side panel) of your computer case, that implies
there is a slight vacuum in the case due to insufficient room
for airflow into the front of the case.
A nice cooler would be a Zalman 9500 AM2 at about $50 USD.
Knowing your motherboard name would make checking the fit easier.
http://www.newegg.com/Product/Product.asp?Item=N82E16835118004
http://www.zalman.co.kr/eng/product/view.asp?idx=202&code=005
http://www.zalman.co.kr/product/cooler/9500AM2_eng.html
But the 9500 really shouldn't be necessary if the case has
good cooling. Test your system with Prime95 (mersenne.org)
torture test or a program like CPUburn, to establish how
bad your cooling problem is. Then decide whether you really
need to buy a product like that. In cooling a computer, the
trick is figuring out the most cost effective place to make
improvements, whether it is the exhaust fan than needs to
be better, opening vent space somewhere, or the CPU cooling
solution. Considering the size of your case, and the
mechanical pieces that might get in the way, you should
spend some time doing 3D analysis, to decide if the
cooler you see advertised, is going to fit in the confines
of the case or not. The Zalman 9500 is big and heavy, and
might not fit.
Also, the AM2 processors are available in various thermal
ratings, at a higher price. But while this article makes
it sound easy to get these, they don't appear
to be all that available. You can find some duals on
Newegg at 65W, which might have helped a bit.
http://www.xbitlabs.com/news/cpu/display/20060322212457.html
http://www.newegg.com/Product/Product.asp?Item=N82E16819103741
Paul
