Why BIG CPU coolers are good!

[lhgpoobaa]

Why BIG CPU coolers are good!
(And don't try this at home)

I have a Overclocked XP1700+ TbredA.
1750Mhz @ 1.70v.
My CPU cooler of choice is a MCX-462 with 3000rpm 80mm panaflo fan ontop.

Yesterday i took my R9700pro out to test it on my GF's computer to try to isolate a problem it's having (unrelated to the CPU).

When i got home i reinstalled the R9700pro, closed up the case and booted up.

I played games for an hour or so, then did some desktop work. During that time the system crashed twice with odd windows glitches.
I thought this was highly unusual as i can usually run for Weeks without rebooting.

Suffice to say when i just had a peek inside my case i noticed that the CPU fan was DISCONNECTED.

Yep. thats right.

<b>I had been running a significantly overclocked CPU at 100% cpu load for at least 2 hours with no fan!</b>
And it didnt BORK at all while gaming. Just while doing desktop stuff with UD cure for cancer running in the background.

The case had a nice hot plastic smell, and the copper base of the MCX-462 was hot enough to burn the tips of my fingers!

When i powered the system back on with the cpu fan now RUNNING i went into the bios and saw the CPU temp was at least 94C, probably alot higher as i had given it 5 mins to cool.

Even so the cpu took a further 5 minutes to get back down to normal levels... thanx to the large mass of very hot copper that had to be cooled.

Did a few tests and the CPU appears to be running fine. No damage done.

So even with no fan the Large and impressive mass of the swiftech MCX-462 kept my Overclocked system up and running for 2 hours at full load.

Now thats what i call good product endorsement!!!
[laughs]

And in future im gonna triple check that i reconnect the CPU fan when messing around inside my beast.

<b>Regards,
Mr no integrity coward.</b>

 

[melb_angel19]

Faaaaaaaaaaaaaaaaaaaaaaaaaaaaaaans!

<b><font color=purple>Males need a minimum of 30 minutes to wind down after work without chatting.
However, females need a minimum of 30 minutes to tell their partner about their day!</font color=purple></b>

 

[svol]

So how did the Radeon 9700 Pro tests go?

Nice to see Emma post here too. .

I love my Delta 60HP 7000 RPM fan that puts out more dB then CFM

 

[TheMASK]

it ahd happened to me once too. i had forgot to connect the CPU fan to the mobo after i installed my CPU. Luckily i keep my case open and when i booted into BIOS i saw that the CPU fan wasnt spinning. i switched off my UPS at that instant. From then on, i double check if the CPU fan is plugged in.

EDIT: and it was not a fancy HSF but the stock HSF that came with the 1700+ t-bred B.

<font color=red>I only write to get more posts...</font color=red><P ID="edit"><FONT SIZE=-1><EM>Edited by TheMask on 08/05/03 02:58 AM.</EM></FONT></P>

 

[Codinerx]

Hahahah thats a funny story, I'm glad the cpu didn't die. And I agree, when it comes to heatsinks the bigger the better hehe.

 

[lhgpoobaa]

Well the CPU is fine. And i love my MCX-462 more than every

The Graphics card however is shagged. It did the exact same sort of crashing on emma's computer, so it seems the card had the glitch right from the start. :frown: Just unlucky i guess.

<b>Regards,
Mr no integrity coward.</b>

 

[lhgpoobaa]

Well how long your cpu can last is very dependent of the physical size fo the heatsink.

More massive the better, and the MCX-462 has gotta be one of the heaviest around. It takes some time to heat the large slab of copper up!

Its why i prefer it over newer lighter but better cooling heatsinks. The new ones may get better thermal transfer ratings, but less mass means greater temp fluctuation and less total thermal capacity.


<b>Regards,
Mr no integrity coward.</b>

 

[TheMASK]

That explains it!! I also have a <A HREF="http://www.thermaltake.com/products/heatsink/v6.htm" target="_new">Volcano 6Cu, Cu-Al hybrid.</A> Its heavy. and the one that came with the 1700+ is light. THe 6Cu has a 5000rpm fan and its very noisy. THe stock one has a 3000 rpm fan and at similar fan speeds (tnx to Asus Q-Fan) both perform almost equal, with my stock HFS performing marginally better sometimes.

So do u suggest i put the 6 Cu back?

<font color=red>I didn't do it, nobody saw me do it, you can't prove it </font color=red>

 

[lhgpoobaa]

Sounds like you need a lesson in thermodynamics and metallurgy.
IIRC the 6cu was never a "great" heatsink. ok, but a bit dated for todays high end coolers.

But given its extra mass it would probably last longer than the much lighter stock cooler.

With stock coolers, ther are a few important factors to consider:

A. Thermal conductivity is very important. How quickly heat can be transfered away from the central core contact patch. Copper is smoewhat better than aluminium, which is why we see copper cored heatsinks.

B. Heat capacity is also important, but more subtle. Larger heatsinks are better, and copper is ALOT better than aluminium. Heat capacity can be defined as how much energy a unit can adsorb to make its temp go up 1 degree.
Heatsinks with a large mass and thus a high heat capacity are slower to respond to energy input changes. And will last longer if the fan fails.
On the reverse side they also take longer to cool from hot.

C. Thermal retention or conductivity to air is a little different. Copper is actually WORSE than aluminium. Aluminium is light, doesnt adsorb heat as quickly as copper but it gives it off better. Copper finned heatsinks need higher airflows to remove the heat effectivly. Thus hybrid heatsinks are common, as well as being cheaper and lighter than all copper ones.

D. Surface area is also important, but it must also be balanced with airflow. Skived 'thin fin' heatsinks are good, but if the fins are too close together the air cannot flow between them easily, leading to a reduction in performance.
It doesn't help that the standard 12v casefan is poor in dealing with high backpressures.
Turbulent flow is also desirable, get better metal to air contact for the best thermal transfer and corrugations on pins or fins gives a greater surface area.




<b>Regards,
Mr no integrity coward.</b>

 

[scottchen]

Well I think the SLK900U is the best of the best.

I hate Computers! My Sapphire 9800pro core/mem speed won't go above 490/790. I really hate computers!

 

[LtBlue14]

<A HREF="http://forum.oc-forums.com/vb/showthread.php?s=&threadid=187162" target="_new">copper is better in all respects, except weight, machineability, and thermal diffusivity, which only has an effect in non-steady state conditions, so once the system has reached equilibrium (which is what we really care about), aluminum's small advantage is gone</A>

<A HREF="http://www.planettribes.com/allyourbase/ayb2.swf" target="_new">411 UR 84$3 R 8310N6 2 U$</A><P ID="edit"><FONT SIZE=-1><EM>Edited by LtBlue14 on 08/05/03 10:11 AM.</EM></FONT></P>

 

[TheMASK]

i siwtched to the 6Cu, but so far, with the fans running at about 3000rpm, the stock HSF performs slightly better. My idle temp with the stock HSF was 41C and with 6Cu it is 43C. Not a major difference. but i hate that noise it makes when i turn ON the system. So i think i'll switch back to the stock HSF.

Oh, BTW, 6CU was the "best" HSF i cud lay my hands on here. There's no other HSF with CU hybird or pure available here.

<font color=red>I didn't do it, nobody saw me do it, you can't prove it </font color=red>