Fancy PC Heat Sinks in MDD?

[trag]

Has anyone here tried installing any of the fancy heat sinks available for the PC in an MDD? I was looking at the nicely organized reviews at http://www.frostytech.com and they provide most of the information one would need to choose a heat sink, once you have measured the available space in an MDD.

Yes, mounting would be challenge. That's part of the fun, right? And with the "wind tunnel" monicker, the MDD is a great candidate for better CPU cooling to keep that 120 mm fan's speed down.

Yes, I've seen the XLR8yourmac articles about fan changes and such. The thing that got me thinking about the heat sink is the fellow who installed the 1.4GHz copper heat sink in his 1 GHz model. But I imagine that service part is no longer available from Apple.

Now, in the dual CPU model, it looks like one would need a heat sink with a base at least 14mm X 55mm. The 55mm is a bit of a guess, but the G4 package is 29mm long and the die is 12 X 10 mm, IIRC. So from center to center on two G4s is 29mm plus the space between, which looks to be about 10mm. So that's 39mm. Then there's the distance from center of package to edge of die X 2, which is just the width of the die, which is another 10 mm. So we're at 49 mm. Then add a bit of margin, though it looks like the stock heat sink doesn't have any margin to speak of, and one gets about 55 mm.

Happily, frostytech's reviews gives the dimensions of the heat sinks' bases. It also gives the length width and height so that one can figure out if it there's room in the case for it. I haven't received the MDD I just bought yet, so I don't have that all-important height dimension yet.

Once one has those things nailed down, it should be an enjoyable task to go through the reviews and pick the best cooling and quietest heat sink which has a large enough base and will fit in the available space.

Then to mount it, I'm thinking an aluminum adapter plate with spring screws. There's a guy on Ebay who will cut any thickness aluminum plate (1/8" up to several inches thick) into any shape you send him and charge you by the pound. He also does steel plate, but aluminum would probably be a better choice in this case. Then one would probably need to drill some holes in just the right places and possibly tap them (cut threads to hold a screw). Neither of those is terribly difficult, just time consuming.

I used his steel plate service to build adapter brackets for the IBM LCD panels I bought. IBM's literature said they had VESA mounting points, but they don't. Now they do. http://www.io.com/~trag/LCD_Bracket/On_LCD_Oblique.jpg

http://www.io.com/~trag/LCD_Bracket/Bracket_Bottom.jpg

Anyway, this sounds like a fun project and I'm wondering if anyone else has tried it. If so, what heat sink did you choose and why?

 

[trag]

Okay, I'm guessing that if anyone has installed a fancy PC heat sink in an MDD that person is not a regular denizen of this forum.

As I think about it, I'll just keep posting in response to myself as I progress through this project. I have a single processor MDD now so I know that 100mm is pretty much the absolute maximum height the heat sink can be without interfering with the drive bay, and that may be pushing it a bit. Certainly that wouldn't leave any room for air flow between the heat sink and the drive bay.

I know that some of the articles on xlr8yourmac.com report installing CPU fans on top of the heat sink and sacrificing that drive bay, or at least one drive's space in that bay, but I'm not willing to do that.

The stock heat sink is about 3 3/8 tall. There's another 5/8" before one runs into the drive bay. At 25.4mm to the inch, that's a smidgen over 100mm. I need to take accurate and detailed measurements and make some engineering drawings so I can fabricate a mounting solution for the PC heat sink(s), but for now I'm working with those numbers.

I took another look at the specs on the G4 package and a picture of the dual CPU module. It looks like the die-edge to die-edge distance on the dual processor modules should be 46 - 49mm.

So a 50mm heat sink base is probably usable. The problem is that the heat sink must then be mounted with extreme precision so that it does not hang over the edge of one CPU's die, and miss covering the other CPU's die.

If someone reading this has one of the copper heat sinks for the 1.4 MHz model and wants to measure the length of the little copper base plate on the bottom, I won't complain if you post the information here.

So I've been browsing modern heat sinks looking for models which have a base plate at least 50mm long in one dimension and which are less than 100mm high. Other criteria are quiet operation, and good cooling. Those last two are rather plastic, because loudness really depends on the fan used. And cooling efficiency is dependent on so many factors, one can't be 100% how a heat sink will work out until one tries it in the target machine.

Still, the reviews give a feeling for the relative abilities of heat sinks to dispose of heat.

I've also found a wealth of useful reviews on silentpc.com. However, they tend to just quote the manufacturer's specs which almost invariably leave out the base plate dimensions. The guy at frostytech actually measures the base plate of every heat sink which he reviews.

If I could go to 125mm.... There are some fantastic models from Scythe which I'd really like to use. Argh, but no, I won't give up the ATA-100 bays, or more importantly, two of the four total hard drive bays. I'm gonna need those later.

Sooo, these appear to be my heatsink choices so far:

Thermalright SLK-948U

Thermalright XP-120

Thermalright SP-97/94

Thermalright XP-90/c

Scythe Samurai SCSMZ-1100

Scythe Andy Samurai Master SCASM-1000

OCZ Tempest

Spire DiamondCool II SP741B3

Enzotech Ultra-X

Akasa AK-873

And we should probably add in Apple's copper, heat-piped 1.4 GHz CPU heat sink as well, though the only ones I've found for sale at this point are $100.

The above choices have the following comments. The SLK-948U is an old heat sink with no heat pipes. But it was a good performer in its day. It's worth a try, though I'm not sure I can even find one for sale at this point.

The XP-120 is one of the best options, I think. With a 25 mm X 120mm fan on top it will be 88mm tall, which leaves a bit of breathing room at the top. It has five heat pipes and performed well in SilentPC's cooling tests.

The SP97 and SP94 are again older sinks which may not be available any more. Their performances in SilentPC's tests were mediocre by today's standards and I think they were more or less replaced by the XP-90 and XP-90C. Still, if I happen to find them at reasonable prices I'll give them a try.

The XP-90 is smaller than the XP-120, has 4 heat pipes and performs almost as well as the XP-120 at high fan speeds--which means it would be bit louder for the same cooling, probably. It also sticks up to 96mm which doesn't leave much clearance for air flow. Hence my greater hope for the XP-120.

The Scythe Samurai Z rev. B is reputedly a nice performing heat sink. It has only 2 heat pipes and the thing sticks up to 98 mm, so it is pushing the physical boundaries. However, Scythe has quite the reputation as a designer of effective heat sinks so it's worth a try.

The Scythe Andy Samurai Master is actually 25mm too tall with the top mounted fan. However, by removing the fan it will just fit at 100mm. Then I could try mounting a fan or fans to the side(s) of the heat sink. This would not be as effective as the downward blowing stock fan, but it might be effective enough. The Andy Samurai Master is one of Scythe's top four heat sinks.

The other attraction of the Scythe heat sinks is that they're both available at Newegg for under $30 and under $40 respectively. Many of the other heat sinks are only available at "boutique" computer cooling shops at premium prices.

The OCZ Tempest is a solid performer (according to reviews) with a super-smooth base and a height with fan of only 78mm. It looks like I'll have to mail order it from Walmart though, who I'm more or less morally opposed to. Anyone know another source?

The Spire DiamondCool II SP741B3 has a gigantic base over 90mm long and is only 77mm high with its fan, but it also performed very poorly in review testing, yielding a temperature rise about 20C worse than the other heat sinks under consideration here. But it will fit in the space and that is rare enough to get it considered.

The Enzotech Ultra-X would be 13mm too tall with the fan mounted on top of the fins, but I think I can mount the fan under the fins. The 4 8mm heat pipes (most heat sinks' pipes are 6mm) raise the aluminum fins high enough above the base that there's probably room for the fan between the base and the fins. The Ultra-X only rose 24C above ambient under a 125 Watt load while producing only 40dB of noise. This one looks like the other best choice along with the XP-120 mentioned earlier.

The Akasa AK-873 is another poor performer (in reviews) who is here mainly because it fits. It is only 75mm high, which is nice and has a very long base (74mm) which will make fitting to dual processors less finicky. It has two 8mm heat pipes. In the review test under 125 Watt load it rose only 28C above ambient, but that was with a fan blowing hard enough to make 60 dB of noise. At a more reasonable 37 dB of noise the reduced air flow let the heat sink rise to 47C above ambient.

If you figure ambient around 80F (27C) as a worst case and that the fan starts speeding up around 58C, then the heat sink can only afford to go about 30C higher than ambient before the fan gets louder.

47C would be way out of the ball park. 28C would be just within, but with the heat sink's fan putting out 60 dB, who cares if the built-in fan spins up?

Okay, that gives me 10 heat sinks I can try, although I may not be able to find three or four of them still for sale. The hard to find ones are also one's which are older technology or performed poorly in reviews so not finding them would not be a great loss.

Then there's the stock aluminum finned heat sink and I'd like to test the copper heat piped heat sink from Apple if I can find one for signifcantly less than $100.

I think I can take internal temperature measurements for comparison using these remote probe digital thermometers they sell for aquariums now. They're only $7 or $8 each, as opposed to the $30 jobs I've seen sold for computers.

And I guess I should come up with some way to measure loudness. How expensive is a decible meter? Hmmmm. Could I rig something up with an old 68K Mac (Q605?) an Apple microphone and some recording software. Perhaps recording software which will report the decibles of the stored recording? It might not be very accurate in an absolute sense, but would it be accurate for one measurement relative to another?

Finally, I need to fabricate some adapter bracket or brackets to let me mount these heat sinks to the MDD. I am hopeful that one adapter will fit all. After all, they're all meant to mount in the same geometry of PC, so if I can adapt from that geometry to MDD geometry, then my adapter may fit all the heat sinks involved.

The problem is I planned to use this Ebay seller: anthony8045, who will cut plate steel or aluminum to any shape you request at very reasonable prices. He dropped off of Ebay within the last few weeks. If his service is a available, then making an adapter is just a matter of careful measurements and drawings of the parts involved, a little skull sweat about how to adapt one to the other, and then an engineering drawing of the needed part sent to Anthony along with a bit of money. Oh, there's holes to be drilled and possibly tapped when it comes back, but that's not so hard.

 

[MacJunky]

Hum, you know... If you will be using an adapter plate between the stock mounts on the MDD and the new HS then you don't really need the new HS base to line up perfectly.

Not a MDD but perhaps interesting?

http://www.macmod.com/content/view/21/193/

 

[trag]

Hum, you know... If you will be using an adapter plate between the stock mounts on the MDD and the new HS then you don't really need the new HS base to line up perfectly.

The problem is it does need to line up perfectly in one dimension for the heat sinks which have bases only 50mm long. The distance across the two dies of the dual CPUs is a smidgen less than 50 mm. If the HS is not aligned properly, one CPU will be overlapped adn the other CPU will not be covered.

In the other dimension, placement does not require precision, because the die is 12mm long and the heat sinks are typically 37mm wide or more.

Not a MDD but perhaps interesting?http://www.macmod.com/content/view/21/193/

What I can see of it looks interesting, but the html or java or whatever is written so poorly that there's a sidebar on the right side covering up the text, such that I can't read it.

Is there a better link?

 

[~tl]

Not a MDD but perhaps interesting?http://www.macmod.com/content/view/21/193/

What I can see of it looks interesting, but the html or java or whatever is written so poorly that there's a sidebar on the right side covering up the text, such that I can't read it.

Is there a better link?

Aside from the first couple of paragraphs which have the Google ads over them, the rest is still readable. It's only the edge of the last letter of each line that is touching the black background...