CPU temps, case temps, fans

[Tuvoc]

Hello everyone

My system:

Globalwin 802 largish mid-tower case
1 inlet fan, one exhaust fan - both fairly mild and quiet and running off mobo connectors
Abit KT7A
Athlon XP 2000+ with Akasa AK-821 2Q Silent CPU Cooler. Very quiet.
Case temp 34 degrees
CPU temp full load "folding" continuously 53-57 degrees

I'm not happy with these temps, although system is nice and quiet and 100% stable.

Now to the strange bit.

Took the side panel off the case, figuring that case temp was too high and that if I brought that down the CPU temp would come down also. To my surprise, after a few minutes the case temp remained exactly the same, but CPU temp dropped dramatically to 48-50 under full load. I powered the system down for a few hours and powered it up. Case temp started at 23 degrees which is about right, but after "folding" for a while rose up to the 33-34 degree mark again. CPU temp 48-50, excellent

Now, the system is pretty quiet, so in theory could leave the case open, but I'd like to close it again if possible.
If I believe the case temp sensor, case ventilation isn't a problem as it is the same open or closed. BUT opening the case does drop the CPU temp to an acceptable level so that is contradictory. Could be the positioning of the case sensor I suppose.

So:

Q1 If I replace the two case fans with powerful ones running from the PSU connectors, is this likely to be the answer ?
With a fairly large case, how do you get good airflow ? The case only has cut-outs for one fan front and rear so two really beefy fans seems to be the only answer.

Q2 Also, the rear case fan sucks air out across the top of the CPU cooler which sits quite tall of the mobo. Does this decrease the efficiency of the CPU cooler in any way ?

Q3 CPU cooler should be adequate, anyone any experience with it ? Could change it, but I'd rather not

And if you've got this far reading this message, many thanks, and even more thanks if you will reply !!

[SJP]

OK, let's get the basics out of the way...

Your case temperature shouldn't be more than 7C above ambient (AMD specs).
Your CPU temperature, under full load should be around 20C above case temp with an average cooler (obviously better with a large copper cooler, less with a piddly-little Aluminium cooler).

Case cooling benefits CPU temps, plus HDD, Vid-Card, sound card and MoBo and so should be the starting point. case cooling is also (generally) cheaper than improving CPU cooling.

To minimise your case temperature, first start by tidying cabling. Rounded IDE/Floppy cables are a good idea too. Try to provide a clear air-path from intake to exhaust.

Your two existing case fans should really keep the temperatures down more than they are. make sure the lower/front fan is sucking in, and the top/rear fan is blowing out.

See how you get on with that lot, the next stages are a little more involved, but hopefully your case temps should be around the high twenties, and your CPU the high fourties.

[Tuvoc]

Thanks very much for the reply.

The case fans are blowing the correct way.
I'll take a look at the cabling, good point. But the case is quite tall, so the exhaust fan at the top back and the inlet fan at the front bottom are a long way apart.

I've just ordered two YS-Tech fans which I've used before in another system I've built before. They are noisy, but have incredible air flow. I'll see if that improves things.

My second machine sits just a few feet beside this one, and the case temp in that is 27C. Different mobo so perhaps not directly comparable. But that is a noisy machine - two strong fans and a noisier Coolermaster cooler, and in a smaller case where I think the air just races through the smaller space with the two fans. The 1800XP in that peaks at 48C.

I guess the old compromise between noise and cooling effectiveness. Can't have both a quiet and a cool PC - at least not that easily.

[SJP]

the case is quite tall, so the exhaust fan at the top back and the inlet fan at the front bottom are a long way apart.

That shouldn't matter too much. Warmed air naturally rises (convection), and so the fans are there to aid this process. Blowing cool air in at the base, will displace the warmer air above, which in turn will be extracted by the top fan.

I've just ordered two YS-Tech fans which I've used before in another system I've built before. They are noisy, but have incredible air flow. I'll see if that improves things

Sounds good to me. I have five YS-Tech fans in my case, including a 120x38mm running to 135cfm. So long as they have a free air-path (no punched grills or cables butted up against them) they're not too noisy.

Can't have both a quiet and a cool PC - at least not that easily.

Too true. A RheoBus can help though, allowing you to run the fans at 7v most of the time, but ramp them up to full speed when needed. eBuyer sell the Sunbeam Rheobus for around £17.50, which is the cheapest I've seen one in the UK.

[Tuvoc]

OK:
Removed both existing fans. Front case fan was probably not working too well as the filter was clogged with dust. Both were YS-Tech but rated at 1.2w, so very weak. Marketed as silent which was true
- Speed - 1850RPM
- Output - 27CFM
- Decibels - 20dBA

Gave the case a good vacuum, cleaned the filter. Put two new YS-Tech fans in there, rated at 2.76w
- Speed - 3000RPM
- Output - 45.2CFM
- Decibels - 34.2dBA

Result ?
1) Lot of noise !!
2) But temps under control now.

Case temp peaks at 30c now instead of 35c before, typically sitting at 28-29C and CPU peaks at 52C instead of 57C.

So, temps OK now, at the expense of noise.

Before, with the case open, CPU peaked at 50c. Have to say leaving the case open and with quiet fans or perhaps just the one fan is quite a good option....