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#11
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CPU Cooler designs?
"Vanguard" wrote in message ... "Mitch Crane" -three wrote in message .. . "Ron Krebs" wrote in news:GglRg.1011$fl2.452@trnddc02: I was under the impression that you just want the hot air drawn off the components. I'm not so sure I'd want cool air pumped over my CPU. What happens when a cold front hits a warm front? I'm not suggesting it would rain inside my case, but wouldn't condensation come into play? My box will be in an AC environment and sometimes that cool air is actually cold. Now maybe the hot components stay hot enough to evaporate that, but just to make sure, I'll throw a couple of silicon packs in the bottom of my case. Think that'll help? : ) When the cool air hits the warm stuff inside the case it will get warmer and the relative humidity of that air will drop. If you had cold stuff in the case and you were pumping warm outside air onto it then you might have a condensation problem, as can occur with some extreme phase-change type coolers. Guess Ron forgot that the air is *dryer* in winter when the air is colder hence the higher sales of humidifiers in winter. Silicon packs are useless when air is moving. They are used in sealed containers to remove what moisture is there and would be *trapped* there. I sure did. Problem is, I don't run my box outside in cold, dry winter air. Nope, it's in an AC environment where they run plenty of humidifiers. And I'm disappointed my attempt at humor with the silicon packs was taken literally. I guess I'll have to make a bigger smiley next time. Cheers, Ron |
#12
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CPU Cooler designs?
"Ron Krebs" wrote in message
newsrARg.1486$KK.159@trnddc08... "Vanguard" wrote in message ... "Mitch Crane" -three wrote in message .. . "Ron Krebs" wrote in news:GglRg.1011$fl2.452@trnddc02: I was under the impression that you just want the hot air drawn off the components. I'm not so sure I'd want cool air pumped over my CPU. What happens when a cold front hits a warm front? I'm not suggesting it would rain inside my case, but wouldn't condensation come into play? My box will be in an AC environment and sometimes that cool air is actually cold. Now maybe the hot components stay hot enough to evaporate that, but just to make sure, I'll throw a couple of silicon packs in the bottom of my case. Think that'll help? : ) When the cool air hits the warm stuff inside the case it will get warmer and the relative humidity of that air will drop. If you had cold stuff in the case and you were pumping warm outside air onto it then you might have a condensation problem, as can occur with some extreme phase-change type coolers. Guess Ron forgot that the air is *dryer* in winter when the air is colder hence the higher sales of humidifiers in winter. Silicon packs are useless when air is moving. They are used in sealed containers to remove what moisture is there and would be *trapped* there. I sure did. Problem is, I don't run my box outside in cold, dry winter air. Nope, it's in an AC environment where they run plenty of humidifiers. If it is cooler inside your PC's box than outside, why are you pumping warm air into it to cause condensation problem? |
#13
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CPU Cooler designs?
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#14
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CPU Cooler designs?
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#15
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CPU Cooler designs?
On Sat, 23 Sep 2006 23:06:52 +0100, Gerry_uk
wrote: Hi, As I understand it, most ATX style PC setups have a fan above the CPU that blows air down onto the CPU to keep it cool, and the hot air bounces around inside the PC case until it can find an exit (if it's lucky). As I see it, there are two problems with this, a) unless you have a vent in the side of the PC case, the air being taken in by the CPU cooler will not be cool, because it's air from inside the PC case? b) the hot air from the bottom of the heat sink ends up warming up the Motherboard? I was looking at the Dell CPU coolers of the GX280, GX620 workstaions (Intel P4 / Pentium D) and the PE2400, PE 2600, PE2800 servers (Intel Xeon). The design is completely different. The air is sucked in from the front of the case, straight over the CPU and out of the back - how cool is that? Pretty cool, and there's hardly any noise either. So what ?? That's exactly the way it is in conjunction with my rear case fan and vented front-panel with my Zalman9500 @ 1600RPM on my X2 4400+ ( o/c'd to 2.6GHz, absolute max. case temp 48 degrees C). Cools the memory very effectively as well. The Zalman design is quite brilliant for its efficiency and smart airflow pattern while still only slightly over the CPU manufacturer's max. recommended heatsink weight. Which is no worry on my A8N32-SLI with the provided board-stiffener in the CPU area. I am not familiar with the Dell hardware you describe ? BTX-style by any chance ? In which case a high-performance video card will nicely bake in the exhaust air from the CPU and memory area. Not surprising in a totally CPU-centric motherboard design from the same wizards that brought you the hand and foot-warmer called the P4-Prescott. John Lewis -- Gerry_uk |
#16
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CPU Cooler designs?
wrote in message
... On Mon, 25 Sep 2006 06:54:20 -0500, "Vanguard" wrote: The point is to continually "change the air" inside your case to keep your components cooler. Whether you have air blowing in (and the air inside air is forced out) or you have fans blowing out (and outside air is drawn in) really makes no difference. I have fans blowing in near the bottom and the fan near the top, including the power supply, blowing out. I saw a case mod where the guy had a duct from his AC going directly into his case and it still wasn't raing or iceing up in there. Because your friend had the smarts to blow *colder* air into the case so there would be no condensation when it hit the warmer parts. Blowing air out the side panel means you are sucking in pre-warmed air over the CPU before exhausting it. Blowing air into the case directly at the CPU means you get the greatest temperature differential. Since the PSU is nearby, the air warmed by the CPU gets drawn out and exhausted through the PSU rather than over the memory sticks or chipset. Either just use a hole and shroud with the existing CPU fan or use a case fan with shroud in place of the CPU fan. Do no have a case fan next to the CPU fan (but if you feel the need then make damn sure they blow in the SAME direction and not at or away from each other). One of the fans will end up restricting the other regarding maximum airflow. If one blows more CFM than the other then the lesser CFM fan acts as resistance to the higher CFM fan. This is the same reason why you need to make sure your case's air intake matches or exceeds your case's exhaust rate since you can't push out more than you can suck in (although some have said a slight positive air pressure inside the case reduces dust accumulation, but I've never measure the amount of dust collected in my case and simply realize that I need to blow it out twice a year). Remember that while a greater temperature differential, using water-cooled systems, peltier setups, or whatever that you are simply increasing the possibility of cooling your components as much as possible. You can't cool them faster than the thermal interface allows; i.e., you could easily use excessive cooling beyond which the heat cannot transfer across a metal plate any faster, so the extra cooling is wasted. Similarly, for air cooling, buying a CPU fan that is rated 50 CFM won't push that amount of air through the restrictive air space between the heatsink fins (the fins cause turbulence and the airflow has to take a 90-degree turn both of which equate to resistance). You might find a 25 CFM fans cools just as well as a much noisier 50 CFM fan. In fact, I've seen CPU and case temperatures drop in some cases by reversing the backpanel fan so it is an intake fan rather than an exhaust fan (its normal position) but you need to test in your own case. |
#17
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CPU Cooler designs?
On Mon, 25 Sep 2006 22:38:03 -0500, "Vanguard"
wrote: Blowing air out the side panel means you are sucking in pre-warmed air over the CPU before exhausting it. Blowing air into the case directly at the CPU means you get the greatest temperature differential. Since the PSU is nearby, the air warmed by the CPU gets drawn out and exhausted through the PSU rather than over the memory sticks or chipset. Blowing air in (or having no side fan at all) results in the most pre-heated air flowing over the memory or chipset. Granted, the air might be slightly cooler. The key to reducing warm air flowing in circular or counterproductive directions is to not interfer with the time-tested and proven chassis airflow pattern from bottom front to mid-top rear. By reducing the bottom front intake rate, by use of a side intake if not another method, there are lower velocity flow everywhere except into the 'sink. The exhaust fans will exhaust at same rate (providing front intake was sufficient) but a short-loop is created, any air not exhausted into the air most immedate to the exhaust fan will take a longer path till exhausted, and slower. Side intake is mostly Intel's attempt to ship cheaper heatsinks with P4, particularly Prescott CPUs. A properly set up system has no need for the side intake and is usually as well off having it blocked completely. The CPU is not the only part that needs cooled and the heatsink selected for it should be selected so as to do the job acceptibly without other parts running warmer as a result. Remember that while a greater temperature differential, using water-cooled systems, peltier setups, or whatever that you are simply increasing the possibility of cooling your components as much as possible. You can't cool them faster than the thermal interface allows; Untrue/non-applicable. The thermal interface doesn't allow or disallow, it is only a decrease in efficiency of transfer from the warmer to the cooler part. This warm vs cool is the key element as mentioned below. i.e., you could easily use excessive cooling beyond which the heat cannot transfer across a metal plate any faster, ... False. If the cooling isn't much better, the difference may not be significant change in temp (only a little), and the CPU may not have needed to run cooler at all, BUT it will run cooler with a better cooling system and exact same thermal interface, because the better cooling results in the cooler of the two parts (warm vs cool), being cooler than it would have been. Thus, the thermal compound with the same thermal transfer efficiency, is seeing a higher temp differential between the two parts which must necessarily result in a cooler CPU (all else being equal, same thickness of thermal grease, flatness of mating parts, contact area to top of CPU, etc). ... so the extra cooling is wasted. It might easily be wasted money, time, even materials to throw away the stock sink (and years(?) later this 2nd sink) if there wasn't a specific *need* to get the CPU any cooler (like in an extremely hot environment or high overclocking), if it ran cool enough to be stable and have acceptible lifespan, OR if the improvement in the cooling was minimal, such a slight drop in temp that it varies more by ambient room temp than anything else. Similarly, for air cooling, buying a CPU fan that is rated 50 CFM won't push that amount of air through the restrictive air space between the heatsink fins (the fins cause turbulence and the airflow has to take a 90-degree turn both of which equate to resistance). A higher free-air rated fan will not push the free-air volume through a heatsink, that much is true. On the other hand, given a similar fan (dimensionally matching the other fan and heatsink and at least as thick) that has the higher CFM from higher RPM, that will result in more airflow through the 'sink. Perhaps not a lot more- these fans have relatively low static pressure potential, but even a little more, will directly correspond to a reduction in heatsink temp, which as mentioned above, will ultimately cool the CPU more. Increasing airflow has a quickly diminishing return though, Seldom is it worthwhile to have a fan faster than around 3000 RPM unless a special circumstance or very poor fan (typically undersized or at least too thin for the application). Often it is desirable to have even lower RPM, it can be acceptible to have CPU slightly hotter to significantly decrease noise if the margin allows for it. You might find a 25 CFM fans cools just as well as a much noisier 50 CFM fan. If all else were equal, no, it is impossible. If the diameter of fan or thickness, or even an entirely odd proprietary fan design were used on same heatsink, then these other factors would have to be considered as well, but taking same exact fan one can vary the voltage to produce different RPM - airflow (airflow will increase so long as the fan isn't terribly undersized and already at it's practical maximum flow rate into the pressurized area in the 'sink) and see the temp change. It may not change a lot but it is an inescapable scientific truth that to whatever extent this air (which is cooler than the 'sink) flow is increased, there will be a corresponding decrease in 'sink fin temp, conduction away from the base of the 'sink to this lower temp region of the fins, and through the thermal compound to the CPU. The conduction efficiency does not change with the fixed variables (grease, heatsink metal) but across mediums (CPU to 'sink or 'sink to air) the higher temp differential does always result in lower temp. Naturally if the temp difference is minor, especially if being reported by a motherboard-mounted sensor, it may be so slight a change as to be indiscriminable. I am not suggested anyone improve their cooling at all, unless it is overheating. In fact, I've seen CPU and case temperatures drop in some cases by reversing the backpanel fan so it is an intake fan rather than an exhaust fan (its normal position) but you need to test in your own case. This should never be done, it necessarily increases temps of other parts (unless the case was otherwise unusual in it's airflow before this fan was flipped over). Cooling a CPU is not a game where lowest number wins. Anyone who has a stable system and CPU that doesn't die prematurely, "wins", so long as they deem the noise level acceptible. However, while keeping the CPU cool enough, focus is then shifted to the rest of the system - a CPU is more heat tolerant than many parts. |
#18
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CPU Cooler designs?
Hi kony,
A properly set up system has no need for the side intake and is usually as well off having it blocked completely. Perhaps, but here's something to try. Run your ordinary ATX fan cooled PC for two hours in the summer including some time under load. Measure the CPU and MB temps, then remove the side panel near the CPU, watch the temps FALL like a brick! -- Gerry_uk |
#19
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CPU Cooler designs?
Blowing air in (or having no side fan at all) results in the
most pre-heated air flowing over the memory or chipset. Granted, the air might be slightly cooler. Ah, who needs fans? For peace and quiet you want one of these: http://home.att.net/~Tom.Horsley/zooty/zooty.html Proof that you can easily spend as much to get quiet as gamers spend to get the fastest graphics :-). |
#20
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CPU Cooler designs?
"kony" wrote in message
news On Mon, 25 Sep 2006 22:38:03 -0500, "Vanguard" wrote: Blowing air out the side panel means you are sucking in pre-warmed air over the CPU before exhausting it. Blowing air into the case directly at the CPU means you get the greatest temperature differential. Since the PSU is nearby, the air warmed by the CPU gets drawn out and exhausted through the PSU rather than over the memory sticks or chipset. Blowing air in (or having no side fan at all) results in the most pre-heated air flowing over the memory or chipset. Granted, the air might be slightly cooler. Slightly cooler? Try 15 C cooler. While my room temperature is 20 C, the inside temperature is 35 C (no, I haven't gotten to modding my home PC's case yet). Actually I prefer a quiet PC so I let Speedfan slow down the fans which lets the inside get hotter unless temperatures exceed the configured thresholds whereupon the fans speed up and are more noisy. Cooler internal temperatures would mean cooler air over the CPU (and GPU). Having to push warmer air over the CPU means less efficient cooling. If I can get MORE cooler outside air inside the case then there would be fewer times when Speedfan would have to speed up the fans. The key to reducing warm air flowing in circular or counterproductive directions is to not interfer with the time-tested and proven chassis airflow pattern from bottom front to mid-top rear. Time-tested? Time has shown that the ATX case was NOT designed for best cooling. It provides absolutely no zoning of airflow. In fact, it stupidly enforces turbulence because of the twisting required for the airflow, and turbulence is resistance to airflow. Do you see any ATX-style cases that have channels built in to keep flat cables out of the way so they don't block the airflow? Why did they design it so hard drives could be shoved against each other (so there is no airflow between them)? Low front intake is okay for drives in the lower cage but not in the upper drive cage. ATX (without modification) is a poor design for cooling. By reducing the bottom front intake rate, by use of a side intake if not another method, there are lower velocity flow everywhere except into the 'sink. The exhaust fans will exhaust at same rate (providing front intake was sufficient) but a short-loop is created, any air not exhausted into the air most immedate to the exhaust fan will take a longer path till exhausted, and slower. Short loops are exactly what are needed for zoning the airflows to minimize them from intermingling with each other. Cool the hot stuff first with direct outside air and expel it immediately. Side intake is mostly Intel's attempt to ship cheaper heatsinks with P4, particularly Prescott CPUs. Wrong. Side intake was to circumvent the ATX spec's poor airflow design. The CPU is not the only part that needs cooled Exactly, so why use the same airflow to cool EVERYTHING? ATX is a poor design for cooling. Modders knew that for a long time before case makers starting adding the extra intake/exhaust ports. In fact, I've seen CPU and case temperatures drop in some cases by reversing the backpanel fan so it is an intake fan rather than an exhaust fan (its normal position) but you need to test in your own case. This should never be done, it necessarily increases temps of other parts (unless the case was otherwise unusual in it's airflow before this fan was flipped over). Not if you add MORE venting, like adding a top grill and a bottom fan that pushes air up past the rear of the drive cages and over the memory sticks. Top venting may simply be using a PSU that has a grilled front face instead of just a few slits. I get much better cooling for *everything* by zoning the airflow inside the case. The CPU gets cool air from the side panel and its heated air passes out through the backpanel grill (using shrouds). The daughtercards (i.e., video) get their own shroud to pull in air from the side panel intake and out through a rear grill over the cards (get a fat case to add the grill or buy one with it already there). Add a grill to the bottom with a fan to blow up and past the backside of the drive cages and over the memory sticks (add a top grill if you feel the PSU's fan isn't adequate or it doesn't have a grilled front face). Keep airflow as linear as possible and minimize turbulence (which includes changes in direction). Many cases don't have fans at the front (unless YOU add them) but instead just passively suck in the air based on the effective rate of the exhaust fans. If you now add an intake port midstream in the case, as in the case of a side panel intake fan, the exhaust fans will be expelling a portion of that air and drawing less in from the front. You might end up having to add a fan at the front or around the hard drives to make sure they get sufficiently cooled, too. If the exhaust fans were expelling 30 CFM (as their maximum) but a new hole is added at the side that inputs 10 CFM, the exhaust fans are still only going to expel 30 CFM so 10 CFM less is coming in from the front to cool the other parts. So, yeah, I see your point but my point is that the ATX design sucks for cooling. Better cooling was NOT why the ATX spec was developed. Almost everyone has seen that taking off the side panel and simply pointing a table fan into the case lowers temperatures significantly, so regardless of the ancient ATX case design, you could use side panel intake fans to better cool your system provided there was an equivalent rate of exhaust and you don't mind the noise of the extra fans. The ATX design doesn't cool that well so sometimes we have to mod the case to cool *better*. The old ATX design tried to use one major airflow pattern to cool off everything. Remember that the first ATX spec had the PSU blowing air into the case and they later decided it was better to have the PSU fan suck it out. If you read the ATX 2.1 spec (http://www.formfactors.org/developer/specs/atx2_1.pdf), all it says about airflow is "Chassis venting should be placed strategically to allow for proper cooling of other components such as peripherals and add-in cards." Oooh, wow, what a scientific airflow design ... not! ATX was designed for *cheap* integration, not for best cooling. The only part of the spec that addresses specific airflow is in the placement of the PSU and its fan in close proximity to the CPU to quickly expel the heat generated by the CPU so doesn't travel to warm up other components. Don't get too hung up on claiming the ATX case was designed for a particular airflow pattern for best cooling. Its spec was NOT designed for best cooling and its up to you to mod the case (or get one) based on YOUR cooling needs and component placement. Obviously you could mod it wrong but it's pretty easy to mod it right and get far better results than what the ATX spec was designed for which itself tells you to mod according to your needs. Designers came up with BETTER cooling designs while sticking within the ATX footprint, that's why there are cases with extra intake/exhaust ports (but not all have them strategically placed). If the ATX design really had considered cooling, it would've zoned the areas to be cooled where, for the hottest components, outside air is drawn immediately to a hot component and expelled immediately without it mingling with any other airflows. If you're hot and sweaty, do you turn on the fan and stand on the other side of the room? Do you stand behind some other hot and sweaty person or go get your own fan? Cooling can be VASTLY improved over the ancient and inadequate ATX-style case. If you can cut plexiglass (and heat to bend it, if needed) and glue it together to make your own shrouds (or find a kit that works for you), along with nibbling to add fans and intake/exhaust grills, you can zone your own case and get it running almost as cool (for EVERYTHING) as you could by simply removing the side panel and pointing a table fan at the innards. |
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