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Accelerate Your Mac!
Reader Review: Quantum Atlas 10K RPM U2 SCSI drive
By Paul J. Tetreault, Jr.
Published 8/27/99

Part Two: Temperature Monitoring and Cooling

10,000 RPM in an 8500?

The 64 dollar question for owners of vintage Macs with relatively small internal case cooling capacity is whether it is okay to stuff hot, fast 10,000 RPM drives inside their boxes. Before the Atlas 10K, the answer was a definite no. The Cheetah is just too hot to mount inside an older Mac like an 8500 without extensive modifications to provide additional cooling. That limitation may no longer apply, thanks to the Atlas 10K's far superior heat signature. In any event, it is an objective question that you can answer by monitoring temperatures inside your computer.

Apple's data sheet for the 8500 lists the allowable operating temperature range as topping out at 40 C. Whether any device is acceptable for internal mounting then ultimately boils down to the question of whether you can provide adequate air flow to maintain an internal temperature below 40 C.

Taking a peak at temperatures inside your box may also alert you to other potential reliability problems that you can solve - it sure did in my case. Until I discovered the temperature monitoring devices below, I ran an older Seagate Barracuda, model ST 15150N, internally in my 8500's lower bay. I knew the drive was hot but I didn't know how hot. The drive was mounted with an APS triple fan drive cooling assembly, but the drive's height was so high the assembly was largely ineffective. I got suspicious when I began to hear bearing noise from the 8500's fan, alerting me that it was working overtime. When I put one of the thermometers shown below on the drive, I discovered it was about as hot as a cool Cheetah, it was running at over 44 C!

Who knows how much I may have shortened the life span of my 8500 before I removed the old Barracuda? And that's the point, you can't make decisions about what to mount internally unless you have good information on the internal heat conditions inside your computer.

Neat Tools!

All you need to check temps inside your computer is a thermometer on a wire, and Radio Shack has two neat models you can choose from, shown at right.

The black model provides a simultaneous readout of temperature at the remote sensor and at the unit and records the minimum and maximum temperatures observed. The white unit's display can be switched to show temperature at the unit or at the remote sensor. Both have 10 foot long cords on their remote sensors and can be switched to display in Centigrade or Fahrenheit. Both also come with adhesive strips for mounting and easle-type supports so they can stand on their own.

If you're not fluent in switching between C and F in your head - or if you can't even remember the formula - the one other thing you need to conduct heat analysis is a chart that will let you visually see where your data lie. You can drag the chart shown below to your desktop and open it in your browser or any program that can display gifs. To make your own, just plug the following data into your spreadsheet and make a chart:


On the left is Radio Shack's $19.95 indoor/outdoor car thermometer, part no. 63-1023. On the right is their $14.95 indoor/outdoor thermometer, part no. 63-1009A. The car thermometer is backlit and includes battery.

Mounting and Measuring

My skunky old 8500 with a remote sensor wire strung out of the power switch hole.

Below and at right are photos that show how to mount the remote sensor on a hard drive and one way to route the sensor wire out of the 8500's case. I simply removed the on/off switch assembly, leaving the hole through which its activation rod passes open for the wire. The sensor can be placed in different spots inside the case to check for hot spots or measure the temperature of specific components.

To monitor a drive, place the sensor either directly on top of the drive itself, or in the air stream above the drive, depending on which you are trying to measure.

To monitor drive temperature, place the sensor directly on top of the drive. The sensors and their leads are insulated - you can place them anywhere as long as they're clear of moving parts.

Cooling the 8500

Ready for 500MHz! - The APS triple fan assembly mounted to cool the 8500's PCI and processor cards.



Just Coolers - if you can use a drill, an Xacto knife, a soldering iron, and a hot glue gun, the fans and hardware in these hard drive cooler kits can probably handle just about any cooling problem you're likely to have.



There are two types of power connectors that will attach to the power supply leads inside the Mac. The unit on the left has a parallel power connector. One end attaches to the leads from the power supply, the other end to the hard drive. The unit on the right has a pass through connector that plugs directly into the hard drive. The power supply leads plug into the same connector.



The finished product, a 10,000 rpm hard drive running at 27.2 C. The black thermometer shows outside air temperature on the left, and a temperature of 27.6 C inside the 8500 - well within the 40 C spec!

Necessity is the mother of invention, and as we add more cards and internal components to our aging Macs, it may be necessary to improvise cooling inside the case. Shown at right is how I put the APS triple fan assembly back to use after removing the hot old Barracuda it was attached to.

The fans are mounted on the fold-up plastic clip that secures PCI cards in place and grounds the heat sink on the G3 upgrade card. The fans are held in place quite simply with telephone hook up wire. It ain't elegant, and at this point it really isn't necessary, but at least I'm prepared when the time comes to drop a faster, hotter processor card in the box. My 8500 now runs consistently at 3 degrees Centigrade over the room air temperature - about 26-30 C.

The cooling system design in the 8500 case is actually quite sophisticated. The system operates at negative pressurization - drawing air into and through the case, rather than just blowing air into the case as many PCs do. The internal fan in the power supply is regulated by an internal temperature sensor and speeds up as the box gets hotter inside. With my hot old Barracuda pulled and its fans installed cooling my Miles 2 and RailGun, the load on both the power supply and the fan has decreased.

PC parts stores and Radio Shack sell a variety of fans from the very small with embedded heat sinks for cooling graphics chips to large case fans. Cooling products are also available on the web. One such vendor I've found is ComputerNerd USA, Inc. Their Cool-it Dude Heat Control Products page lists a variety of things from fans to thermal paste that Mac users can easily adapt to fit specific needs. I have not done business with ComputerNerd so I can't give them a first-hand recommendation, but their catalog has pictures so it is a great place to shop. Storage Review's June review of the Atlas 10K also provides a link to their own test of a number of cooling products, with pictures.

Mac-specific cooling products are also available. In particular, Proline manufactures a number of replacement bezels designed for removable drives that with a little ingenuity can be adapted for fans. The largest opening in the Proline bezels for the 8500 is 1.3' X 4" which is not large enough to hold the Just Cooler's (see photo at right)) removable filter and grill, but could probably accommodate the flat part of the cooler that holds the fans. Proline also makes internal RAID kits that include heat conducting aluminum brackets and fans.

Cooling the Atlas 10K

If you add a readily available hard drive cooler to Hyper Microsystem's external case, you can lower the Atlas 10k's operating temperature to the chilly 27-29 C range. Shown at right are two "Just Coolers," a set of two fans designed for a standard PC 5.25" hard drive bay. Hyper Microsystems sells these coolers for $15 on their miscellaneous accessories page, and your local PC parts store probably has them in stock at about the same price.

You'll notice there are two different models shown. The unit on the left is the HD-100, which has smaller fans and a a parallel power connector. On the right is the HD-120 with larger fans and a pass through power connector.

Using the right type of connector may be essential if space requirements are tight. In the external enclosure provided by Hyper Microsystems for the Atlas 10k, there was no room for the pass through style connector behind the hard drive. But since there was plenty of room in front of the drive, I decided to use the larger fans. You can swap connectors by just clipping the wires from the fans you want to use and attaching them to the connector you want to use, observing the color-coding scheme and insulating any bare wires. It may be even easier just to shop at your local parts store and find a set of fans that has the right connector.

Hyper's external case includes three different types of bezels to cover the drive compartment opening in front of the drive. Hyper normally ships the drive with a blank bezel - no opening - so be sure to tell them to include all the bezels. The one you'll use to add a cooler to the front of the case has a 1 & 9/16" X 4" opening to accommodate a removable drive. The opening is the perfect size for the Just Cooler's essential components, the fans and grill.

To install the Just Cooler, simply cut off the cooler's mounting arms so that the flat front face of the cooler is just wide enough to fit in the bezel opening. Place the trimmed frontispiece into the bezel and secure with a bead of hot glue across the top and bottom of the cooler, INSIDE the bezel. The finished product is shown at right, running at a cool 27.2 C.

So could you mount a 10,000 rpm drive inside your Mac? The answer depends on the specifics of your machine, but now you know how to measure your computer's internal heat load and make an informed decision. And you know that there are a variety of cooling products that with a little ingenuity may add new life to your vintage Mac. Of course, you could always just get an external drive and take it with you when you buy that G4.

- Paul J. Tetreault, Jr., Esq.

Feel free to send me questions - can't promise I'll have the answers
but what's great about Apple users is we help each other!

Back to Part One - Atlas 10K Performance Tests

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