Anyone tested CPU temps with passive vs. active cooling?

[Ken90630]

Sorry for the double-post, everyone. If the moderator sees this, he can delete the first one.

There's a new thread today here on this forum about how quiet some retail PCs are (Dell, et al.). The issue of noise vis-a-vis active and passive CPU cooling came up as a result. I posted a semi-related question several days ago about CPU cooling ducts. Unfortunately, that thread got sidetracked and I never did really get an answer. :-(

Anyway, I was wondering if anyone here has ever tested CPU temps with active vs. passive cooling. In other words, active as in a heatsink/fan combo cooling the CPU, and passive as in one of those plastic ducts over the CPU/heatsink [w/no HS fan] that acts like a vacuum and merely sucks hot air away from the CPU and channels it to an exit fan (sometimes via a sealed tube).

Member Cerb mentioned something to the effect of passive schemes like this resulting in temps running "20 C" hotter than active schemes with a heatsink fan. As far as I know though, I've never heard of Dell having any problems with machines dying early due to constant excessive heat (in fact, system longevity is one of Dell's known attributes, isn't it?).

Has anyone ever done a test with both methods on a particular CPU to see which really results in lower CPU temps?

Just curious.

Ken

PS: Before you ask, I don't work in the computer biz and don't have test equipment. If I did, yes, I'd do the testing myself!

 

[mechBgon]

Dell uses a low-RPM 92mm fan to pull air through the heatsink's fins, so it's not really what you could call passive cooling... the fan isn't physically attached to the heatsink, but there's a fan nonetheless. Off the top of my head, I don't know of a commercially-available ducted setup like that.

If you did want a very quiet cooling setup (case + CPU), then a Thermalright SLK-800A or an Alpha PAL8045, combined with a Panaflo L1A 80mm fan, would be pretty decent for CPU cooling, and perhaps an Antec Sonata if you like its physical attributes (the door over the drives can be a nuisance for some people). I'm assuming you're on track with the AthlonXP plan still

A possible fly in the ointment is the hard drive. Some drives use fluid bearings, some use ball bearings, some models might come with either type depending on the whims of the manufacturer. (edit: fluid bearings = better, they are more consistent and don't get noisy with age) A system's only as quiet as its loudest component, so a noisy hard drive or video card will negate all the quiet stuff. If you want low noise, Seagate's 7200.7 hard drives are very quiet indeed. I've got one in my home system, and I just launched Defragmenter, and can I hear anything happening down there? No. But I won't claim that it's that great of a performer, either... the 7200.7's are relatively slow due to their slow seek times. I heard lots of good remarks about the Hitachi models that have 8MB of cache, though (quiet, and good performance too).

Hope that helps

 

[Ken90630]

Yeah, technically you're right, Tom. You know what I was thinking though: "passive" as in no fan directly over the heatsink blowing air onto the heatsink in the 'traditional' way. But a fan pulling hot air away from the HS/CPU, albeit farther away, does make the set-up "active," I suppose. Well spotted.

I'll have to take a look at the Thermalright & Alpha you mention. Am not familiar with them yet. Re the Panaflo fan, I actually bought a Silencer 80mm fan from PC Power & Cooling that beats the Panaflo in both CFM of air moved and also noise (barely), with ball bearings & a lifetime warranty. It's a close call, but IMHO the PCP&C one wins by a nose when comparing all relevant specs.

Re the HD, I bought a Western Digital 40GB w/8MB cache for this build 'cuz it was the only drive on the market (that I could find) that's this small WITH an 8MB cache. There are bigger drives with the 8MB cache, but I didn't want to spend the $$ for them as all I really need with this particular machine is a very small drive. Heck, if there were a 20GB HD on the market with an 8MB cache, I'd have gotten that! My call to Western Digital about whether or not it has FDB yielded a response of "Well, it's hard to say for sure ... some might have the FDB and some might not. We're transitioning to FDB on some of our drives right now, and it just depends on what batch your drive came from." My heretofore stellar opinion of WD took a bit of a hit with that answer ....

Oh, and yeah, I'm still on track with the Athlon XP plan for this build. I've been doing my research and acquiring components one by one. I now have everything except the mobo, CPU, video card and monitor. I've just been really busy with other things (regular "life" responsibilities) and haven't had time to nail everything down. You'll know I'm back in gear when I PM you a half dozen times with BIOS questions (ha ha).

Last time I checked, my monitor questions in the video forum were being ignored for the most part, so anyone who wants to click on over & help me some more, feel free (hint, hint). All I really wanna know is whether or not Web pages created for a particular resolution will fill up the screen on a given monitor if the monitor's native resolution is higher than the res the page was created for (without doing any scaling). Got all that? I think I know the answer, but I feel like I'm missing something.

I'd still like to see a test of CPU temps comparing an active vs. passive cooling scheme. I just think that green duct on the Dell I saw recently looks like such a great way to move CPU heat straight outta the case before it has a chance to heat the whole case up. But with no HS fan blowing onto the CPU, what's the actual CPU temp? THAT is the $64,000 question .... Members "Connoisseur" and "Cerb" posted some interesting replies to my duplicate post of this question (why it appears on this forum as a double-post in two different places is a mystery to me!). I'm gonna briefly reply to that thread shortly.

As always, thanks for all the info.

 

[mechBgon]

The Alpha would be a good match for your Silencer fan as long as you don't mind that it's a real beast to install/remove. It uses the four bolt-holes around the CPU socket to mount through the motherboard, meaning that installation (and often removal) of the heatsink requires taking the whole motherboard assembly out of the case. Thermalright offers models that bolt through the motherboard, and also models that clip down in the usual way. Not all motherboards accept the Alpha PAL8045. Fit list is here and I even know the ultra-secret link to where you can order spare mounting hardware for it :Q

As you can tell, the Silencer fan makes next to no noise. So it seems to me that there isn't much to gain by making the rear fan do all the work via a duct, if you can have the Silencer on your heatsink and have better cooling with essentially no additional noise. Heck, it's even paid for already But if you wanted to try the ducting thing, get the Alpha, install it, but leave its fan shroud off and make your own duct that leads to your case's rear exhaust fan.

Regarding the web-page/monitor question... depends on the web page. Some expand, some stop at a certain width and just leave white space on the right.

 

[Ken90630]

Actually I bought the 80mm Silencer to use as an exit fan on the rear of the case, with or without a duct. (I bought it before I even started thinking about this duct stuff.) Sorry I didn't clarify that. I hadn't even thought of using it as a CPU cooler, but now maybe I will. It puts out 27 CFM -- do you think that would be enough for the Athlon XP 2500 or 2600 I plan to get?

Am too tired tonight to check out the Alpha links you mentioned, but I'll give them a look-see tomorrow. And anything that's "ultra secret" demands my curiosity.

I knew you were gonna say that about the Web page question, but you didn't really answer my question (no offense!). Lemme re-frame the question this way:

Let's say I have a 20" LCD monitor. Twenty-inch LCD monitors have a native resolution of 1600 x 1200 (at least the 10 or 12 I've researched all do). Now, let's say I log onto a Web site like DumbComputerQuestionsLikeThis.com and the page designer has designed the page to be "best viewed at 800 x 600 resolution." We've all seen that ridiculous statement on some Web pages, right?

Now, correct me if I'm wrong, but that page is gonna fill up only part of my screen (referring only to left-to-right screen fill here, not top to bottom). There's gonna be a lot of empty space on the right side of the 20" screen unless I manually scale down the monitor's native resolution to 800 x 600, right?

Theoretically, every page I look at on the 20" monitor (with its 1600 x 1200 native res) will have empty space on the right side unless the page was designed to be viewed at 1600 x 1200 resolution or higher. Right? So here's what I'm trying to confirm in my mind: Given that virtually no Web page designer is likely to ever design a page to be "best viewed" at 1600 x 1200 resolution ('cuz the masses are using mostly 15" and 17" monitors that can't go that high), is there any point in having a monitor any bigger than, say, 17" or 19" for surfing the Web? What would be the point if you're always gonna have unused, empty space on the right side of the screen?

I pose this question with the idea that said computer will ONLY be used for Web surfing & e-mail, with no need for larger screen "real estate" for MS Office or desktop publishing programs or anything else. Now whaddya think, Tom? Am I thinking correctly here or am I off base? And what did you mean when you said, "some expand"? I feel like I'm missing something ....

PS: I'm aware of the slightly increased "viewable area" I'd get vertically with a bigger monitor, but let's leave that out of this particular discussion. I'm just interested in the other issue of left-to-right screen fill.

 

[NervousNovice]

The SilenX series fans give you 36 CFM at 14dBA link

 

[Ken90630]

Yeah, but that's a 92mm fan. The one I was referring to from PCP&C was an 80mm fan. You're comparing apples to oranges.

You're on the right track though, because SilenX also makes an 80mm fan that moves 28 CFM at 14 dBA (!). That's phenomenal and beats my PCP&C Silencer, which moves 27 CFM at 20 dBA. Only reason I didn't buy the SilenX one was that they use a cryptic description for the fan's bearings (what does "Hypro bearings" mean? Ball? Double ball? Viscous? Sleeve? Whiskey-damped?), and they don't say what the warranty is either.

PCP&C's site doesn't specify the warranty on the Silencer either, but I was on the phone with them ordering a PSU and the guy assured me they're guaranteed for life. Guess I'll take their word for it until I have reason to do otherwise.

Price differences? A dollar or two (irrelevant).

I gotta say though, if anyone can find another 80mm fan that moves 28 CFM at only 14 dBA like the SilenX one supposedly does, I'd like to see it!

 

[Dman877]

I dunno if I believe those numbers, 28 cfm at 14 dba? doubtful. No sites review fans though so its a wash. Thing is they don't qualify those specs, 14 dba at what? 1 meter? 10 meters?

 

[Ken90630]

Yeah, I wondered about that too as I kept typing -- that's why I went back and edited my post to say "supposedly" towards the end!

I don't suppose a "case fan shootout" might be in the offing on Anandtech.com anytime soon? (Hint, hint.)

Like you say, most of these mfgrs don't qualify their specs, so how're we supposed to know how they were arrived at? All I know is the Silencer I bought is as quiet as I need it to be, so I'm happy.

I'm encountering a similar situation right now trying to compare pixel-response time specs of LCD monitors. Seems there's zero requirements for testing and for qualifying the numbers, and different mfgrs publish different numbers arrived at in different ways. So all we can do is guess and hope. A little more ethics in this business would be nice sometimes.

 

[mechBgon]

I'd definitely recommend getting an LCD with a 4:3 aspect ratio such as 1600 x 1200 or 1024 x 768, if you might run it a lower resolution than its "native" one in day-to-day stuff. Get someone to demonstrate a native 5:4 monitor (1280 x 1024) at 1024 x 768 and I think the problem will make itself apparent, particularly if you use a wallpaper that makes distortion apparent (a circle will become an oval, for example).

 

[Ken90630]

Thanks, Tom. I specifically want to avoid ever running it at anything other than its native resolution. From everything I've read on the subject, image quality takes a huge hit on LCDs when they're run at anything other than their native res.

And we're on the same page re aspect ratio: a 4:3 model it will be. Don't have any need for widescreen for this particular set-up.

If you have time, I posted another question last night on the duplicate post of this topic (still scratching my head over how this happened in two different places ....). Would like your thoughts if/when you get a chance. I'm soooooooo close to figuring this out. Just need a bit more education on it.

I've been bugging the h*ll out of you lately with all these questions, so don't bother if you don't have time.

 

[NervousNovice]

I found it hard to believe at first for a 14 dBA 92mm fan. I've never used any of them but will try it out soon.

There are some website reviews of the SilenX product, e.g. their 14 dBA psu. A search in Google should give you some links.

 

[Ken90630]

A Google search for SilenX reviews might be a good idea. I'll add it to my ever-growing list of things to do.

Let us know what you think if you get one of those 14dB fans.

Ken

 

[NervousNovice]

I've grabbed some links from Google

SilenX 14 dBA psu reviews:

Overclockers Club
EXTREME Overclocking
Techware Labs
Silent Pc Review
eXtremeReviews.net

That psu comes with a single fan "rated at 19 CFM, 1500 RPM, and 15.9 dBA".
SilentPcReview said that "you have to keep additional hot air from other case components from getting into the PSU in order that its fan remain spinning as slowly as possible" and "with caution about its low airflow fan". Oh man!

SilenX 14 dBA fan reviews:

Overclockers Club
Tweaknews.net

 

[NervousNovice]

Oh yea! I'm going to get a 120mm and a 92mm SilenX case fan by the end of next week. I hope they will do a better job than the Vantec Stealth fans.

 

[0roo0roo]

as long as you compensate for cfm loss from duct and force the same amount of air through, the cooling is the same. prebuilt lets em know exactly how much minimum cooling they need. no overclocking, so no need for extreme cooling. its a trade off they make.

 

[Ken90630]

Nice job with the reviews research, Nervous Novice. You just saved me some time. You're the man!

Think I'm gonna order a couple of the SilenX fans and try 'em out. I heard Papst makes nice fans too, but I haven't had time to check that out (and they're supposedly very expensive).

After you get your 120mm and 92mm SilenX's, let us know what your firsthand opinion is.

Ken

 

[0roo0roo]

if your going to use low flow, make sure ur case fan holes are as free as possible