View Full Version : The final word (stacking vs cooling)

09-10-2001, 09:49 PM
Ok I have seen this suggested but never saw any definitive answers

Here's what I want: Across the bottom of my G4 DA case I have 4 drive bays 3 on the floor and one stacked (which I will call bay #4) I want to put 3 18gig x15's in there in bays 1, 2, & 4 with my very cool running ATA IBM 60 gig in bay 3. Since the IBM produces very little heat I am thinking that it would not damage the x15 mounted directly above it and this will also put the top of all 3 x15's exposed to further reduce the heat that they generate. So what's the word oh wise ones? Would this be safe for the ultra expensive.....err I mean Ultra 160 drives?

I am also considering moving the IBM to the space above the DVD drive. I have done this before in my B&W g3. I had TWO 7200 rpm 1st gen cuda sca drives up there and shortly after installing I also installed TWO 2 inch fans, this was right after I burnt my fingers :-) Had 5 drives in that case and 3 pci cards (one a V5) and had no power supply problems.

As for power IF I overload the PS I just happen to have an LCII that has a power supply small enough (I think) to also fit above the DVD drive. This is a hard power type that has a physical switch built into it. I just need to find the pin-outs on the MOBO connector of the LCII to run a drive or 2 from it.

Am I insane?

[This message has been edited by Damien (edited 10 September 2001).]

09-11-2001, 01:18 AM

You lost me on the G4 DA, is that a QuickSilver DP? Obviously no problem with the X15s in bays 1 and 2 on the floor. The X15 in bay 4, the ATA IBM in bay 3 may be cool running with nothing so close on top of it, but with the scant clearance between drives in bays 3 and 4, the IBM may run hotter and cook the logic board of the X15 above it. If you can figure a way to elevate the X15, that would be better.

Can't elevate it much because the fan case on the back wall interferes, but every little bit would help, about a 1/4" or more I think before the fan case interferes. So the total clearance would be 3/8" to 1/2". I couldn't get my ruler in there to measure exactly, but I think you could get 1/2" between drives if you can figure a way to elevate the X15 more. I would think that would be enough, but magician is not in favor of stacking an X15 on top of the ATA drive. As far as overloading your power supply, what does it say for max watts? FWIW, k

09-11-2001, 09:17 AM
I would welcome input on a variation of this question. I want to use 3 x 73G 10K Cheetahs inside my G4/733 in the same bay configs you have discussed for the X15s. Do you think that a 10K drive might be OK sitting above the 60G ATA, or is the problem only related to the heat build-up in the ATA drive when another drive (of any sort) is above it??

Thanks taffy.c

09-11-2001, 10:14 AM
I have read elsewhere in this forum that the older 10k drives produce more heat than the newest 15k drives.

As to my issues I guess I will have to put that IBM on top of the DVD drive. I was looking last night and there is plenty of room for both the drive AND the LCII power supply if I need it.

Does anyone know the pin-outs on that LCII mobo connector?

My G4 is the highest end Digital Audio version. The G4 733 with the L3 cache and the Superdrive. Charcoal and Ice colored.

[This message has been edited by Damien (edited 11 September 2001).]

09-11-2001, 10:18 AM
Actually I do have a drive stacked on top of my IBM 60 gig. It is a Maxtor 40 gig ATA 7200. Both drives run just barely warmer than roon temp.

if it makes a difference My Mac is in a room with central A/C & heat.

09-28-2001, 06:14 AM
Damien, I've been doing basically what you want to do for some time now. I have three ST39204LW 10K Cheetahs and one IBM 75GXP series in a Gigabit G4 DP500. It works pretty well. The Cheetah stacked on top of the 75GXP has plenty of clearance (somewhere between 1/4" and 1/2", I'd have to take it out and look to be sure). Both it and the 75GXP stay lukewarm to the touch when the ambient temperature is similar to a air conditioned office environment.

Caveat: X15s do use more power than the 39204LW (about 3-4 watts more apiece), so my experience is no guarantee that you'll do as well.

During summer heat waves they get much warmer than lukewarm, of course, but not enough to be harmful. I downloaded the Seagate tech manual for the 39204LW and found out what the acceptable operating temperature was: no more than 50 degrees C measured at a certain spot on the case, with up to 65 degrees allowed for short periods, and other measurements on specific ICs on the PCB. I've satisfied myself via the Mk. 1 finger that at least the HDA case testpoint is never exceeding 50 degrees C. (The human pain threshold is about 40 C, and I can always hold my finger on the testpoint indefinitely.)

Actually, it's the single drive located in the front of the machine in "bay 1" which gets the hottest in my experience -- the large internal fan sitting near bays 2-4 helps circulate air over those drives and the PCI cards.

I started out with this gear in a B&W G3 (aka Yosemite). It ran noticeably warmer there; over time Apple has made some small tweaks to the case design that improve airflow. (One that I noticed is extra intake holes for the large internal fan.) Hopefully the G4 DA case is another improvement.

#1 key to Yosemite style cases: Make sure your cabling doesn't clutter up the air cavities in the middle of the computer. If it does, it will reduce how much air moves through the computer as a whole. I've found this to be more important in the Yosemite style cases than anything else, to the extent that it's generally a win to tape cables down on top of drives to force them to lie flat, even though that tends to insulate the top surfaces of the drives.

#2 key: put the computer on a hard flat surface. There are air intake holes punched all along the underside. Block them and you block a nifty path for cool air to enter the machine and flow past the hard drives. There's also some conduction from the drive frames to the mounting plates to the case bottom. So it's a good idea to have free airspace clean of dust bunnies underneath the computer.

Come to think of it, the bottom cooling is probably another reason the bay #1 drive gets hotter: it is raised off the floor with cables running underneath it.

10-03-2001, 03:10 PM
i am, as k intimated, very conservative where these issues are concerned. I would myself only stack IDE drives in bays 3 and 4 (Apple itself numbers the internal bays in this way), unless i were satisfied (like tim) that aggregate heat is within limits. The problem, as i see it, is that stacking drives leaves the controller of the top drive directly above the spindle of the lower drive: the most vulnerable part of the top drive is directly adjacent to the hottest part of the lower drive. I do not trust Seagate's method, where a specific corner is tested and used as an indicator of drive temperature. Some commonsense is mandated here, though i admit i do tend to err on the side of caution where drive cooling is concerned. We are talking, after all, about my data, and even though i have redundant backups, losing a drive entails inconvenience and down-time, even if we're only talking about 30-minutes to swap a drive and restore data to it from a backup. I would rather use that 30-minutes to watch Seinfeld, or take a long hot shower.

now, it is possible to stack a drive on top of the DVD, but i have a couple of comments there, as well.


firstly, the commercial kits for mounting drives there use velcro to secure the drive, and it must be noted that velcro can be conductive. I have never heard of anyone zapping a drive mounted there, but it doesn't mean that it isn't feasible. Secondly, one of the primary reasons why drive mounting hardware is important is because it firmly holds the drive stationary during spin-up. This is not the time when you want a drive to jerk, or move, as the actuator heads track or the spindle cranks the platters up to 7200 rpm, or 10, or 15k. If you think about it, we are talking about a little bit of torque here, and you do need to ensure that your drives are nice and secure. A jolted drive can result in crashed heads, damaged media, and lost data--not to mention a ruined drive.

so. You can mount a drive there. Apple doesn't endorse it, and unless you do it right, i really don't either. Again, i am weirdly conservative on this stuff. I guess I really am getting old.

in my personal machines i like to install just two LVD drives in bays one and two, and a pair of IDE drives in bays 3 and 4. And that's it. I see no problem running three LVD drives in bays one, two and three, but i personally would not stack an IDE drive on top of a Cheetah there in bay 4. It's just my preference, FWIW.


10-04-2001, 12:06 PM
I just tried this config yesterday with my G4-800DP with a digital indoor/outdoor thermometer, Radio Shack. Two G2 X15s in the left and center bays. Original WD Caviar 80GB ATA/100 in the right lower bay, another ATA/100 drive on top of the WD in the right upper bay. I have a hi-output 80mm fan sucking air off of the X15 in the left bay, and blowing towards the other bays. The outdoor probe of the digital thermometer I mounted to the rear wall large fan lower left screw, essentially over and between the center and right bays.

Typically this config runs 16.7F above room temperature measured by the thermometer's indoor sensor. Worst case yesterday was 18F above. After shutdown, the temp inside the box rose another 2.9F. After an hour of shutdown, the inside temp was still 10F above room temp. After two hours, the temps were the same. Tight box. Not especially happy with the overall cooling of the box. I have never had a computer get this hot. I left A/C off yesterday, above 100F in the shade outside the room window, 81.7F room temp, so typical box temp of 98.4F, worst case 99.7F, peak after shutdown 101.3F (98.4+2.9). k

10-04-2001, 12:50 PM
I had thought that in bays 3 & 4 The x15 should be the one on top as the ATA drives produce virtually no heat to damage the scsi controller on the x15 and this would leave the top of the x15 open to dissipate the heat from the hotter x15

I have a 60gig IBM beneath a 40gig maxtor both 7200 rpm and they are not hot at all barely even warm...

10-08-2001, 07:19 PM
Damien, exactly. I don't advocate stacking a high speed SCSI drive underneath an IDE drive in the double-stack bay at all. I've only done it the other way around, with the SCSI drive on top. (Aside from the heat issues, it would be kind of difficult to get the SCSI cable to a drive on the bottom without replacing Apple's teeny IDE cable with something longer.)

Magician, I agree about those brackets for mounting on top of the CD/DVD. Furthermore, heat rises, and that space is at the top of the case, and is unlikely to have much air circulation unless you install some extra fans.

Also, I'm fully aware that testing one point isn't a complete test. Seagate's tech manual calls for instrumenting that spot (a flat point on the housing above the SCSI/power connectors) *and* several ICs with thermocouples or other sensors. I just haven't felt the need to check things out to that extent since the finger tests give me enough of a "lukewarm" fuzzy http://macgurus.com/infopop/emoticons/icon_smile.gif that it doesn't seem necessary. Were I a system integrator with paying clients, or this something more important than my personal home computer, I'd do more rigorous measurements.

10-08-2001, 08:26 PM
I have never had a computer get this hot. I left A/C off yesterday, above 100F in the shade outside the room window, 81.7F room temp, so typical box temp of 98.4F, worst case 99.7F, peak after shutdown 101.3F
Maybe you should move north? Or how bout an undergound palace? http://macgurus.com/infopop/emoticons/icon_biggrin.gif

Tim_s has interesting remarks - as I just fumbled through an Apple manual (to find out how to install a ZIP in a Sawtooth and QS Mac) - it has his exact description of folding and laying the drive cable on the drives to increase airflow. I would think that a hot drive could ruine a nice EXPENSIVE scsi cable (and I bet GRANITE wouldnt be too pleased to see a burnt one) - but maybe today's drives are cool enough?

I think the 2nd gen 15K Cheeteahs are pretty hot vs. the 1st Gen, but maybe that is only the 36GB model?

I do not think I will have any money for SCSI this go around... damn that Taliban invasion - damn that to hell.

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