Charles Moore's Mailbag

External Western Digital Drives Not Recommended for Booting Any Computer and WiFi Range Reduction

Charles Moore - 2009.04.29 - Tip Jar

Most Western Digital External Drives Won't Boot Macs

From Chris:


Re: Rich

I have a WD My Book Essentials external drive. The hardware used by WD in some of their drives makes them incompatible with booting of PowerPC Macs . . . see here.

As I recall, it apparently has to do with the first device ID (or similar issue) that PPC Macs use to find the bootable drive being used by the front button for one-button backup software (for PCs). They used to have an explanation in the FAQ; now they just list compatibility/incompatibility.


Thanks for the info. Chris.


Unbootable Western Digital FireWire Drives

From DG:

Rich wrote:

"Lee's not the only one to have problems with Western Digital external drives. I've got two that have FireWire but can't be used as startup disks because my machines can't see them at power up, even when the drives are turned on first using external power. Since I've been able to replicate this problem with several Macs, I'm assuming it's something about the WD drives. For what it's worth, I have not tried to use any of the software that they came with: I reformatted and partitioned them right out of the box."

Hi Charles:

For Rich and anyone else that's trying to boot from a recent WD external hard drive, it's not possible. More information on the subject can be found here:

Bombich Software Forums - View Topic - Western Digital drives !!!!! AVOID !!!!

Hope this helps.

Hi DG,

Thanks for the link.


Editor's note: Quotes from the Bombich forum:

"We have had reports of problems with some Western Digital 'My Book' drives due to their automatic spindown (sleep) 'feature'. We understand that WD are unable to offer a solution, i.e. that 'feature' cannot be disabled. The only answer for some users has been to purchase an uncrippled FW drive. 'My book' drives do not respond to Energy Saver settings. LaCie drives, in contrast, have optional auto sleep by a switch; in that 'sleep' they respond to Energy Saver settings and, for example, will spin up when a schedule starts, which the 'My Book' will not do."

And later on, "WD say that none of their external drives should be used to boot any computer." dk

Unbootable Drives Could Be Misformatted

A friend and I were given identical LaCie FireWire drives, new in the box, for use at work. We opened and installed OS X at the same time following the same steps. Mine was bootable, his was not. His would even show under 'Startup Disk' preferences but not at bootup. After multiple attempts at formatting and reinstalling Mac OS X, I noticed the 'Options' button in Disk Utility under Partition. His had a DOS partition map instead of Apple. I changed the partition map and reinstalled Mac OS X. It booted fine. I checked a drive at home that I was never able to use to boot and found the same DOS partition map. After changing to Apple, it now boots fine.


Hi Dennis,

Ah yes. The partition map is absolutely crucial to bootability.

There are several options available for initializing hard drives in Disk Utility. The Apple Partition Map (APM) format is bootable for PowerPC Macs and for Intel machines (while GUID formatted drives will only boot Intel Macs).* That means you have to choose, and switching from PowerPC to Intel can be a pain. I recently had to reinitialize and restore my two main external hard drives, which had been formatted with the Apple Partition Map, to make them bootable with my new Unibody MacBook.

As you discovered, you can specify your chosen partition map option in the Options sheet of the OS X Disk Utility formatting pane.


* Editor's note: You can boot Intel Macs from APM drives, you cannot install Mac OS X to an APM partition from an Intel Mac. You can, however, clone an OS X installation from a GUID drive or partition to an APM one using Carbon Copy Cloner, SuperDuper, or something similar. This can give you a universal Leopard boot drive for both PowerPC and Intel Macs - it worked for me. dk

WiFi Range Reduction with AirPort Base Station

Hi Charles,

There is a way to reduce the range of wireless as Scott asked (Miscellaneous Ramblings Mailbag 2009.04.22). The Apple AirPort Utility has a section called "Wireless Options" which allows one to adjust the transmit power in increments from 100% down to 10%. This could conceivably accomplish his goal of making it more difficult and less attractive for the neighbors to steal your wireless.

In a nod to Earth Day, I will also point out that lower transmit power should equal less energy used.


Hi Dave,

Thanks for the information. That might be all that's needed in many instances.


AirPort Range Reduction

From Russell

You can use the AirPort Utility (Applications > Utilities > AirPort to limit the transmitting power of an AirPort. I have mine reduced to 50% for the same reason as Scott mentioned. There is a small convenience store at the end of our driveway, and someone could sit out there for hours without being noticed.


Hi Russell,

Thanks for the tip.


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Charles Moore has been a freelance journalist since 1987 and began writing for Mac websites in May 1998. His The Road Warrior column was a regular feature on MacOpinion, he is news editor at and a columnist at If you find his articles helpful, please consider making a donation to his tip jar.

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