Could I get some help with my cooling setup, please?

gogetadbl · Sep 2, 2003

My case is an Antec 3700AMB. The mods I have done to it are cut out the metal fan grills and added a duct using a plastic cup. My ambiant temperature is around 27 C. My CPU temp is high 30-low 40 and my case temp is usually low 30's to 35. When I open my case, my system temps jump up to 35 constantly and my CPU temp gets lower by 3 C or so. Some other computers with nearly my same ambiant temperature and lesser cooling achieves better temperatures than what I am getting. I'm using an SK-7 heatsink (applied w/ Shin Etsu G751) with SF2 at max and two 120mm case fans that pump 60CFM on the back and about 40 CFM in the front, as wel as a PSU that sucks up case air and blows it out. I even have one of those PCI slot coolers under my radeon 9700 Pro. The problem I have is that I'm stuck running my CPU at 1.4 vcore and running nearly stock speeds. When I go to 1.7vcore, i get temperatures in the high 40's constantly for the CPU.

Would you guys suggest any improvements for me to try out that could possibly lower my CPU temp?

Trypt · Sep 2, 2003

make sure all your bottom-front fans are intakes, and all your back top fans are exhausts (not just the psu, all back fans have to pull air out).. the cpu fan should always pull air away from the cpu.

khagan · Sep 2, 2003

Do you have a fan on the CPU?? Smart Fan II if not.

sandman001 · Sep 2, 2003

is the duct coming from outside the case? if it isn't I'd drop it as it sounds like it's chocking the SFII.

Also, I'd put the 60cfm fan in front, and the 40cfm fan in back.

slater3333uk · Sep 2, 2003

Well to be honest with you theres not alot you can do

The fact that you say the cpu temp drops after you open the case suggests that you could do with better case cooling but 3C is a small differance and it sounds like you have very good case cooling anyway so i cant think of anything thats going to make a worth while differance

You say you have a sk-7 which is pretty good (3rd best hsink) you could upgrade to a slk-900 with a 92mm tornado fan (loud!) that may bag you a few extra C but its expencive and imo not worth the money

My final point is that you say you cant raise your vcore over 1.4 but i dont understand. Why not? You say at 1.7v you have temps of high 40s but thats quite a good temp for air cooling when your overvolting. You dont need to worry untill you get into the 50s

sandman001 · Sep 2, 2003

My slk-900 and Tornado at about 2600rpm. At my full overclock (2400mhz @1.875vcore), my load temps were hitting 52C. grante dmy room temp was almost 30C, but still. As long as you're stable don't warry about it.

bk94si · Sep 2, 2003

Lap the SK-7 and add a side case fan.

gogetadbl · Sep 2, 2003

Trypt said:
make sure all your bottom-front fans are intakes, and all your back top fans are exhausts (not just the psu, all back fans have to pull air out).. the cpu fan should always pull air away from the cpu.

Yes that is right, except teh CPU fan does not pull air away from the CPu, it pulls air TO the fan.

yes the SF2 is on my CPU , on the heatsink.

I tried switching the two, but there was a temp increase. The front fan has a filter on it also, which kinda restricts airflow. I've been told that having more exhaust than intake is better, so that less dust can acculmulate.

Also on the thing about adding a side fan, I heard it causes a disturbance, take two sine waves out of sync for example.

Trypt · Sep 2, 2003

Your cpu fan should always pull air away from the heatsink, not push air into the heatsink.. this way it removes heat from the heatsink but it also pulls in cool air around the heatsink..

gogetadbl · Sep 2, 2003

Trypt said:
Your cpu fan should always pull air away from the heatsink, not push air into the heatsink.. this way it removes heat from the heatsink but it also pulls in cool air around the heatsink..

I'm not sure if its me, but wouldn't that make the duct useless? Also when I tried that a few months ago, it definately worsened the situation, and the majority of the people on this board say to push air into the heatsink to cool the heatsink, rather than sucking air which can circulate back, plus a duct gets fresh, cool air rather than the hot air inside the case

Trypt · Sep 3, 2003

I am not sure what heatsink you're talking about.. the northbridge likes air pushed onto it, if its a case fan on the side of the case, but if you're talking about a fan directly over the heatsink (attached), then it MUST pull air away from the chipset.. I once mistakenly installed the fan backward and my cpu temp was in the 60's.. i didn't figure it out until a month later when I was installing more memory, and when I switched, it was in the high 40s again, and that with stock cooling.. now that I run a good cooling system, my cpu temp is in the mid 30's. I've never heard of anyone pushing air into the cpu with a mounted heatsink fan, and frankly, it doesn't make much sense.. can you imagine the power supply fan pushing air into the psu? but hey, if it works for you, don't worry about it

bk94si · Sep 3, 2003

gogetadbl said:
Yes that is right, except teh CPU fan does not pull air away from the CPu, it pulls air TO the fan.

yes the SF2 is on my CPU , on the heatsink.

I tried switching the two, but there was a temp increase. The front fan has a filter on it also, which kinda restricts airflow. I've been told that having more exhaust than intake is better, so that less dust can acculmulate.

Also on the thing about adding a side fan, I heard it causes a disturbance, take two sine waves out of sync for example.

1) The fan should blow towards the CPU.

2) If you want less dust you want more intake than exhaust, especially if you are using filters. With more exhaust, you are going to suck unfiltered air through every opening in the case.

3) I don't know anything about sine waves out of sync but I put a 120 enermax fan on the side of mine and it cooled it down a lot (probably 6-7 degrees).

Trypt · Sep 3, 2003

As I said before, I've never heard of cooling any electrical device with blowing air directly on it.. the point is to blow hot air away from the heatsink.. anyhow, if it works for you, so be it.. I have mine set to blow air away, and its at good temps (see sig), in fact the idle temp is lower by a full 22C from stock AMD temp, and at full load it used to go to 70C (prime95 made my computer shut down before), now its at 42C

ZaP37 · Sep 3, 2003

Trypt said:
As I said before, I've never heard of cooling any electrical device with blowing air directly on it.. the point is to blow hot air away from the heatsink..

The only time you should have the fan blow AWAY from the heatsink is when the heatsink has a shroud on it designed to properly direct airflow (for example, the PAL8045). Otherwise you should have the fan blowing ONTO the heatsink.

Think about it: air takes the path of least resistance, so when the fan is blowing away from the heatsink, most of the air going into the fan comes across only the very tops of the heatsink's fins. Also, since the fan's pull is not directed, the air entering the fan (and travelling across the heatsink) is moving pretty slowly. When then fan is blowing onto the heatsink, more air reaches deep between the fins since the air is directed and moving at a high speed.

If you want to verify this, take a fan and hold it an inch above your skin, pulling air away from you. Reverse it, so it blows air onto you. In which orientation does more air hit your skin? Which orientation feels like it cools better?

Blowing toward you.

Trypt · Sep 3, 2003

I understand that, but this is not the case with electrical devices.. like I said, I never saw a manufacturers computer that blows air onto the heatsink, and in the electrical business (power supplies and such) all fans always blow air away from the heat source.. anyhow, i guess it doesn't hurt to try, but as I said, my temp went down 22C from the stock AMD cooling, and I have the fan sucking air away from the cpu.. perhaps I would get the temp even lower with blowing onto the heatsink, i guess i'll try next time i open it up.. but what will it do to my overall air flow?!

slater3333uk · Sep 3, 2003

Well in that case you havent seen very many computers (or "electronic divices" for that matter)

i can assure you that the only exeption to the rule of the fan blows into the hink is cirtan Apha types

You may be right that its not the best way for all setups but for 99% it is

Now back to the attual question - Putting fan on the side panel will reduce tmps but it can be quite noisey (its a bit like fan stacking)

gogetadbl · Sep 3, 2003

My PSU blows air into the PSU, as does my hair dryer. I told you something was fishy blowing air away from heat... could always do H= mc /_\ T and the delta T is far greater between the atmosphere and the source, so more heat dissipates.

Also, more intake means more dust can settle down with more intake, while with more exhaust the dust gets blown out as it enters.

rogerdugans · Sep 3, 2003

It does sound like you have a pretty well executed system, man.
More airflow can be good but I have seen many people (and done it myself

) increase airflow to the point that it helps very little and the increased noise is not worth the small improvement.

You might try ducts or air channels inside the case to ensure that you get airflow exactly where you want it.

Having airflow where it is needed is more important than the total cfm to a degree.

As far as which direction the fan on a cpu heatsink goes:
Try both and see what works best in your system.

BUT-

99.9 % of the computer heatsinks I have seen (and that number is quite large) blow air onto the heatsink. I have two Alpha's that were designed to pull air off but even they are working better in my case by blowing air onto the sinks of my duallie.

99.9% of the heatsinks I have seen reviewed or looked at in stores (online or brick/mortar) also blow air onto the sink.

It may not be the best for electronic components in general but my experience and the market agree: blowing air onto the heatsink works best for computer cpus most of the time.

bk94si · Sep 3, 2003

Blowing in works better because the hottest part (and the part you are trying to cool) is in the middle. By blowing air off the top of the heatsink you are wasting the coolest air at the edges of the heatsink and cooling the center with air that has been prewarmed.

Trypt · Sep 3, 2003

Ok, I switched it already, and the temp is the same, so I guess in my case it doesn't matter.. but now for the conflicting reports on intake/exhaust.. I just finished reading how more intake reduces dust, but gogetadbl just pointed out the opposite. so which is true.. I have 5 fans as of now inlcuding the psu fan.. i have 1 intake at the front, 1 intake at front side down, 1 exhaust in rear psu, 1 exhaust just under psu, 1 exhaust top side back.. this would make more exhaust then intake..

Could I get some help with my cooling setup, please?

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