Using smcFanControl with an Apple Mac Pro

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March 30, 2007

Enhanced Apple Mac Pro Hard Drive Cooling
How to: Use smcfFanControl to Optimize Hard Drive Cooling in the Apple Mac Pro
By Arthur Whalem

Introduction
The Apple Mac Pro is an ultra quiet, powerful desktop computer that can mount up to four internal SATA hard drives using the four aluminum drive sleds. During the AMUG review of the Apple Mac Pro 2.66 GHz, we noticed that if the Mac Pro was fully loaded with four SATA hard drives the temperature levels of the hard drives in bays 1 and 4 were significantly higher than the hard drives in bays 2 and 3. The reason for this is that bays 2 and 3 receive more direct air flow from the top front 120mm fan. The hard drive in bay 1 only gets a reflection of the fan air flow as it sits on top of the fan assembly and the hard drive in bay 4 is the farthest away from the front fan assembly. As a result, hard drives placed in bays 1 and 4 will operate warmer than those installed in bays 2 or 3.

As you can see in the graphic above, SATA hard drive bay 1 is on the left side and bay 4 is on the far right.

Background

The Apple Mac Pro expansion slot/HDD fan seems to stay close to 500 RPM even if the SMART hard drive temperature indicates that the hard drive has reached 122 degrees Fahrenheit. Users can view the RPM of the Mac Pro fans using Hardware Monitor 4.11. As this 120mm fan can provide additional air flow one solution would be to have Apple increase the fan speed when the SMART data from the SATA hard drives indicate a temperature of over 115 degrees. Another solution would be a user adjustable setting for the Mac Pro fan RPM speed. However, neither of these options are currently available from Apple.

When the MacBook was released and some users noticed it was too hot to place on their lap for an extended period of time, the smcFanControl application appeared on the scene. While smcFanControl was originally intended to increase the speed of the fan in the Apple Intel notebook computers, we thought this same application might be helpful for increasing the fan speeds in the Apple Mac Pro.

AMUG contacted Hendrik Holtmann, the author of smcFanControl about this possibility. Within a few months a version of smcFanControl was available that could be used to control the fans inside the Apple Mac Pro.

Cool Running
If you are only using hard drive bay 2 and/or 3 there is really no reason to increase the cooling in the Apple Mac Pro. However, if you want to mount four hard drives in the Apple Mac Pro for an

extended period of time, using smcFanControl to increase the RPM speed of the hard drive fan can provide additional cooling capability.

How it works
To use smcFanControl simply download it and double click on the smcFanControl icon. This will install a new menu item in Mac OS X. Clicking on the menu allows the user to select or create a setting, view the preferences, check for updates or learn more about the product. If users find that smcFanControl is a valuable tool they can also donate to this project.

Opening the "Preferences" menu allows the user to create multiple settings that can be used to control the Mac Pro fan system. The CPU Fan, PCIe/HDD fan, rear fan and the power supply fan can all be adjusted. However, this article only discusses modifying the speed of the PCIe/HDD fan, as the other stock fan settings inside our Mac Pro seem to provide sufficient cooling for our setup.

Fan Performance
In order to test how different PCIe/HDD fan RPM speeds would impact our Mac Pro hard drive cooling, four Seagate 7200.10 320GB hard drives were mounted internally in a striped RAID set configuration. The Mac Pro internal four drive striped RAID set was worked very hard duplicating a 4.2GB folder of video files up to twenty times simultaneously for 90 minutes. The temperature of each hard drive was recorded at the end of the 90 minute heat test. The next process of this test was to leave the Mac Pro turned on with the hard drives mounted for an hour, but with no usage other than temperature monitoring. I wanted to see how well the hard drives might cool down. After resting for an hour, the Seagate 7200.10 320GB hard drive temperatures were recorded. The results are published in the table below.

Mac Pro Four Drive Heat Comparison Test

Mac Pro 2.66	Bay 1 320GB 7200.10	Bay 2 320GB 7200.10	Bay 3 320GB 7200.10	Bay 4 320GB 7200.10
Stock 500 RPM Fan
90 min. Heat Test	120.2	113	116.6	122
60 min. Cooling Test	111.2	105.8	109.4	114.8
609 RPM Fan Setting
90 min. Heat Test	118.4	111.2	114.8	120.2
60 min. Cooling Test	109.4	104	107.6	113
708 RPM Fan Setting
90 min. Heat Test	116.6	109.4	113	116.6
60 min. Cooling Test	107.6	100.4	104	109.4
809 RPM Fan Setting
90 min. Heat Test	111.2	104	105.8	111.2
60 min. Cooling Test	105.8	98.6	102.2	105.8

Temperatures are recorded in Fahrenheit. The ambient room temperature was 79 degrees.

Based on these tests, using smcFanControl to increase the speed of the Mac Pro PCIe/HDD fan to 809 RPM reduced the temperature of the hard drives by approximately 10 degrees Fahrenheit during the heat test. The fan is still quiet while operating at 800 RPM. However, it does produce a slight increase in wind noise that I was able to detect while within two feet of the front of the Mac Pro.

Users that install four internal hard drives inside a Mac Pro can expect the hard drives while active to produce more noise than the HDD fan operating at 800 RPM using smcFanControl. Mac Pro users that want to avoid any additional wind noise should try a smcFanControl HDD fan setting below 710 RPM. During these tests, I was unable to detect any significant additional wind noise with the Mac Pro HDD fan operating at 708 RPM or lower.At the same time, hard drive cooling was improved by 3-5 degrees.

User Fan Control
While the Apple Mac Pro provides plenty of cooling for one or two hard drives, users that want to fill all four hard drive bays will find that smcFanControl is a useful custom cooling tool. smcFanControl cannot equalize the cooling of the hard drives mounted inside the Mac Pro SATA hard drive bays. Hard drives mounted in bays 1 and 4 will still operate warmer than hard drives mounted in bays 2 and 3. However, smcFanControl is able to lower the overall temperature of hard drives mounted in the four bay Mac Pro SATA assembly. With smcFanControl installed on the Mac Pro, users can increase the PCIe/HDD fan speed without impacting the speed of the other fans. This software feature allows users to easily customize the Mac Pro cooling system to meet their individual needs.

Users that want to expand the storage and PCIe capability of the Mac Pro now have a tool that allows them to determine what the minimum fan speeds will be inside the Apple Mac Pro.

Pros
Provides user control of the minimum RPM fan speeds.
Increasing the Mac Pro PCIe/HDD fan speed can enhance hard drive cooling.
smcFanControl is easy to use and install.

Cons
If fans speeds are increased substantially wind noise may be audible.

smcFanControl gets 4.5 AMUGs out of 5!
The Apple Mac Pro provides quiet, high performance computing with room for expansion. With expansion usually comes additional heat. This new tool provides Mac Pro users with the ability to tweak the cooling capability of the computer to meet advanced cooling needs. Complete user control of the Mac Pro internal fan system is an awesome feature. smcFanControl also works with Apple notebooks. Users that are interested in more details may want to check out the smcFanControl FAQ.

Contact Information:
Hendrik Holtmann
holtmann@mac.com
http://homepage.mac.com/holtmann/eidac/software/smcfancontrol2/

Copyright 2007
Arizona Macintosh Users Group, Inc. (AMUG)
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