heatsink size vs cfm

[saimike]

hi guys,

i'm having a hard time finding a good fcpga HSF for my celemine/slotket/bf6 that will not block too many dimm slots. so i was thinking of rigging something up myself that accomplish my oc goals andi'd like to have ur thoughts and experiences about:

1. big heatsink with small fan (perhaps a 10mm vs 25mm)
2. small heatsink with big fan (80mm??)

i'm guess i'm trying to find out which is a bigger contributor to lower cpu temps -- heatsink or fan? thanks a lot!

 

[Tiger]

The following may be helpful;
A big HS will have good heat capacity and will therefore take some time to heat up, in roughly 2 minutes before it tops out and the fan starts to stabilise the temps while a small HS heats up in roughly 30 seconds and tops out. Both will probably achieve the same maximum. Hence it has been difficult over the recent past to rate the HSF's as they all seem to perform to within one or 2 degrees of one another. The factor I believe to be important is the effect of thermal shock on the core. A small HSF leads to rapid heating and this gives rise to rapid core expansion. Its hard to prove but in some work I did about a year ago on a Super Orb and a Global Win showed that the system was far more stable with the Global Win but there was only a 2C difference in the load temp.

 

[saimike]

The following may be helpful;
A big HS will have good heat capacity and will therefore take some time to heat up, in roughly 2 minutes before it tops out and the fan starts to stabilise the temps while a small HS heats up in roughly 30 seconds and tops out. Both will probably achieve the same maximum. Hence it has been difficult over the recent past to rate the HSF's as they all seem to perform to within one or 2 degrees of one another. The factor I believe to be important is the effect of thermal shock on the core. A small HSF leads to rapid heating and this gives rise to rapid core expansion. Its hard to prove but in some work I did about a year ago on a Super Orb and a Global Win showed that the system was far more stable with the Global Win but there was only a 2C difference in the load temp.

this leads me to conclude that: while a smaller HS can be compensated for by a larger F, a larger HS (ever with a smaller F)will lead to better overall system stability.

does everyone agree or have other comments? thanks!

 

[Ugmore Baggage]

I think they limit each other. A big heatsink will absorb heat and then stop, waiting for the heat to be blown away by the fan. The large fan has to have a large surface blow air across to be effective.

A powerful fan will certainly help if you don't have room for a larger heatsink. but of course that fan will itself be larger...

You can gain a tremendous amount by being sure that the air blown across the fins is cool. This generally means ducting air from outside of the case directly to the sink. Also be sure that there's sufficient exhaust high in the case to remove heat buildup.

 

[saimike]

I think they limit each other. A big heatsink will absorb heat and then stop, waiting for the heat to be blown away by the fan. The large fan has to have a large surface blow air across to be effective.

A powerful fan will certainly help if you don't have room for a larger heatsink. but of course that fan will itself be larger...

You can gain a tremendous amount by being sure that the air blown across the fins is cool. This generally means ducting air from outside of the case directly to the sink. Also be sure that there's sufficient exhaust high in the case to remove heat buildup.

thanks for that idea! that should help me out a bit since i have very little space to work with: 50mm height and i block 1 dimm.

if anyone has any ideas for a gd hsf with that height, i'd greatly appreciate it. for now, i'm thinking of mounting a 10mm fan on a sk6 or ax7. ie. underblowing a big HS.

 

[TimDgsr]

I wonder if you could make a higher powered Dell style cooler for your slot, and not block any DIMM slots?

I'm not sure if you could even set it up to run with an overclocked machine, but I guess it's worth mentioning?

here is what i'm talking about:here

 

[LeapingGnome]

I just went through this on my BF6 system... it's much preferable to have a larger heatsink with a smaller fan than vice-versa.

I'm using a Thermalright SK6 w/ 60x13mm 5400RPM Delta fan (28CFM). The combo fits perfectly, doesn't block any dimm slots, and keeps a P3-1GHz running @ 1.3GHz, 36C idle, 45C full load. A full size tower case and two 120mm case fans mounted over the CPU/AGP/memory area also help a lot.

But so far I'm limited to 1.3GHz, any faster and the system is unstable. Not sure if it's the CPU or slotket that's limiting me (it's an MSI-6905 v2.3 slotket). I'm already running at 2.00v and don't want to push it much over that. Sometime soon I'll try an IWill or Abit slotket and see if I can go higher.

Anyway, good luck on your project!

Gnome

 

[saimike]

dam, u guys r immensely helpful here! i want to thank everyone for their comments again!

timdgsr: thanks for that idea, i think its yet-another-ducted-fan approach, but its quite diff from the others i've seen. question: is this a dell thing? if so, which dell's have them? model/cpu (p2, p3 etc) will be useful.

leapinggnome: u're the man! where can i get that combo u have? the sk6 is on my list, but i havent been able to locate a decent 10mm or 15mm fan. where did u find urs? as i understand it, the sk6 fan bracket is meant for 60x60x25 fans, did u rig something up urself or is this a kit? pls let me know, that would seriously solve all my problems! i was going to go for a msi2.0 slotket which someone was gonna sell for $21 shipped, but if u think that ur slotket is holding u back, i might wanna shell out a few more $ for a abit3 slotket. again, i'd be vv grateful if u can share ur experiences.

thanks again guys!

 

[TimDgsr]

that picture is from a dell dimension XPS T-series. it's like a 700mhz pIII. I'm not sure what all models Dell used that style on though.

 

[LeapingGnome]

I got the SK6 from http://www.kdcomputers.com. $22 w/ no fan.

The 60x13mm Delta AFB0612VHC was more difficult to find. After two weeks of trying I discovered a few CoolerMaster heatsinks that come with this fan, so I ordered the cheapest one ($6, DP5-6i31C) from Newegg. After everything was installed there was a few mm left between the top of the fan and dimm slot 1, so you can probably get away with using a 60x15mm fan instead.

As you noticed the SK6 uses fan clips. Since neither of the two included clip sizes will work, what I did was just shorten the 38mm clips by 25mm (the wire is thin and bends fairly easily). It worked like a charm, the fan is very secure.

As for slotkets, MSI's is the only one I've tried so far. Reviews claim other brands can overclock higher (Iwill, Asus, Abit) but until I get my hands on them I won't know for sure. The only suggestion I have is, if you'll be mounting the slotket vertically in a tower case, make absolutely sure it's secured well. Some slotkets have tabs which engage the Slot1 retaining brackets, others don't. Stay away from the latter type.

Gnome

 

[res0r9lm]

I have two computers one is duron 800@950 w/ swifty mc462a and the other is a 1.4 tbird with a swifty mcxc 370 both use ducts the 462a has a 120mm 86cfm fan and the 370 has a 120mm 103cfm fan plus a 80mm 86 cfm fan at the other end. the cw is .15(mcx370)and .18(mc 462a) buy all right the bigger one should be doing better that the little one all it can be is the added cfm.

 

[adamtekh]

a heatsink where the fan is with in the sink might be most suited in this situation

like an orb

or a glaciator

 

[-=UR=- Ranger]

Yeah check out the Glaciator II HS. But I'm not shure if it's less than 50 mm in height. Perhaps someone who owns one could measure his....