Hardware

Start me up: The Macintosh startup process

Schoun Regan explains the startup process for Macintosh computers and the steps that you can take in order to troubleshoot problems.


The startup process is similar on most computer systems. However, troubleshooting startup problems varies somewhat. The point of this article is to shed some light on the Macintosh startup process and to analyze potential problem areas along the way. You’ll see that diagnosing startup problems on the Macintosh is much easier than in Windows. Your mileage may vary, but after reading this article, you should:
  • ·        Understand the startup process of the Macintosh
  • ·        Be able to troubleshoot basic startup problems
  • ·        Save yourself time, money, and aggravation
  • ·        Buy me lunch

But you say, "Wait, I know nothing of the Mac." "So what?" I say. It’s time to learn why they're easier to troubleshoot and repair. So let's find out what happens when you hit that magic button.

The button
Most Macs use soft-startup—that is, they start up from a keyboard button. There were a few exceptions, but I'll begin here. Since almost all Macs used soft-startup, that meant (simple as it may sound) that the first place to look, if a Mac didn't start up, was at the keyboard or ADB (Apple Desktop Bus). The ADB plug might have worked loose from either the keyboard or the Mac itself. Newer Macs face the same type of problem. Introduced Aug. 15, 1998, the iMac uses USB instead of ADB for its keyboard port. Different port, same situation. If you don't hear a fan or a hard disk spin-up, check the cable.

The chime
Most users recognize the familiar Mac startup chime. The chime was related to the Power On Self Test (POST), which tested various pieces of hardware inside the Mac. This testing was accomplished via code stored in the ROM. The hardware that was checked included the logic board, the ROM, all ports and expansion slots, and the RAM chip(s). Things have changed a bit over the years, but certain startup chimes indicate that a Mac has problems. The series of tones indicate the nature of the problem, and while it’s difficult to describe the chimes, a sad Mac face usually accompanies a problem, with a code displayed on the monitor. These chimes are known as the Mac Error Tones and/or Mac Death Chimes. Anything but the normal Mac startup chime is usually related to the failure of a piece of hardware to pass the ROM code self-test. The newer Mac line doesn’t rely on these older tones, but the current startup tone still has variances with respect to hardware problems.

In the past, the solution to problems usually involved hardware replacement. While some lists of error codes still exist, a better scenario is to check the following hardware in the order shown:
  1. 1.      Remove all RAM chips
  2. 2.      Disconnect any SCSI devices
  3. 3.      Disconnect any ATA devices
  4. 4.      Remove any expansion cards
  5. 5.      Remove the video card (newer Macs may give a shortened tone if it’s removed)

Failure to hear a normal startup tone at this point may indicate a logic board problem. Older parts can be ordered from online stores that deal with Macs. Shreve Systems is one such store. You should take newer Macs to an authorized dealer for part replacement or repair.

The startup disk
If you see a gray screen and a pointer in the upper left-hand corner of the screen after the startup chime, your Mac has passed the ROM tests successfully. Now, the Mac searches for a bootable disk. The disk must contain an active System Folder. Macs have a long history of being able to boot from many devices. The early Macs booted from a floppy and were able to boot from any connected SCSI device. As soon as CD-ROMs hit the market, Macs were able to boot from their CDs, starting with System 7.5. The user could start up from a variety of sources. If a Mac had several SCSI devices, the logic board would check each number in descending order for a device with an active System Folder.

To start a Mac from its CD, insert the CD and press and hold C (with older Macs, you also had to press the Command key). Sometimes it’s necessary to bypass the internal drive. Let's say that the internal drive gets past the chime but fails moments later. If a CD isn’t available, the user has to start up from another device. Macs can be forced to bypass the internal drive at startup by pressing Command+Option+Shift+Delete at startup.

If you have a newer Mac with an ATA internal zip drive, you may want to check Apple's tech notes on booting from an internal ATA zip drive. At the time of this writing, some issues exist that concern using these drives as a boot drive. The G4 Macs currently being sold can boot over USB, too, and bootable FireWire is not far behind. All Macs made after (and including) the original iMac can boot directly from an OS X server, bypassing the internal hard drives altogether. The sum of these choices should demonstrate the versatility in choosing a boot disk on the Mac. Remember to open the Startup Disk control panel and choose your appropriate startup disk. iMacs and later will take longer to start up if no disk is chosen.

The System Folder
The next item that you should see is the happy Mac face, which has greeted Macintosh users since the Mac's inception. The face is not just for looks; it indicates a "blessed" System Folder on the startup disk. A "blessed" System Folder means that the System Folder has a System inside it and that the Mac knows it is there. There are times when the Mac loses its blessing, in which cases you start up from another device, drag the System suitcase outside the System Folder, and then drag it back in again. You can see the change in the System Folder icon. I know that it sounds silly, but it's easy and works!

The System suitcase is the one piece of Mac software that usually can’t be replaced with a new version from an installer CD. However, you can make a backup copy on your favorite media and replace the current one with your backup. Again, start up from another device, drag your current System suitcase to the trash, and empty it. Then, drag the backup into the System Folder and restart normally. Windows cannot perform this function, and anyone who has seen it done to fix a Mac walks away impressed. It also speaks to the power of backups.

It’s at this point that a section of RAM has been set aside to hold the System. If the Mac freezes, it may be worthwhile to switch RAM chips, ruling out this possibility. The new Mac family has the startup ROM located in the System Folder. It also can be a source of initial lockups and freezes, and it can be replaced just as easily.

If the System loads successfully, the next item of business is for the Mac to load any patches or updates that may overwrite areas of the System. After a successful load of the System, updates, and/or patches, you get the Welcome To Macintosh (on newer Macs, the Welcome To MacOS) window.

Preloaded extensions
Extensions are bits of code that enable a device or software. In essence, they are drivers. They usually load in alphabetical order and can be seen marching across the bottom of the window as the Mac continues its boot-up process. Their job is to take up as much RAM as possible—or at least, that's the way it seems. Actually, their behind-the-scenes task is to attach themselves to ports and cards and serve as translators for applications that talk to the System. Some extensions provide protocol functionality, while others provide fodder for their Mac owners. These extensions load into the System Heap, the nice area of RAM near the System. Some extensions load directly into RAM, and others sit quietly, waiting to be loaded into RAM when called to duty.

When extensions load, they sometimes ask for a specific area of RAM. If two extensions wish to occupy the same area of RAM, they end up fighting about it, and you lose. The Mac freezes up. You can get lucky and actually see the last extension that loaded, its icon glaring at you from the bottom of the frozen startup window. Often, it’s the extension that doesn’t show up that may freeze the System. To troubleshoot this situation, restart the Mac and hold down the Shift key, which disables all extensions and control devices (more on that later). It’s similar to booting in Safe Mode under Windows. This action confirms that the problem exists with an extension (and/or control device).

You have two choices at this point. You can open the Extensions Manager (a control panel that allows you to turn extensions and other control panels on and off) and begin turning off certain extensions that may be guilty of freezing your System. Or you can restart your Mac and hold down Spacebar, which invokes the Extensions Manager on startup and allows you to perform the same task—just during boot-up. Either way, the idea is to reduce the number of suspected extensions gradually until the guilty party is discovered. If it’s a necessary extension, replace it with a backup copy. If this action doesn’t solve the problem, perhaps another recently installed extension is grabbing the RAM space that the guilty extension needs. Further combinations of extension sets may be necessary to isolate the nasty bugger.

Sleeper extensions
I call extensions that sit quietly and wait “sleeper extensions.” These little dudes don't load into RAM until they’re called by an application. Thus, they’re harder to troubleshoot; however, they do leave clues if you know where to look. Since Microsoft extensions are good at this, let's use them for our example.

Let’s say that my System is taking up 91.5 MB of RAM. (Don't ask why so much; just know that I can do it.) After I launch Microsoft Word 98, my System memory requirements climb to 97 MB of RAM due to several Microsoft extensions that load after Microsoft Word is launched. They were sleepers until they were needed. The problem is that, when they're no longer needed, they sometimes fail to go away. After closing Word, my System occupies 91.9 MB of RAM, or .4 MB more than when I started.

So, imagine this situation during an entire day of opening and closing several different applications over and over. If the extensions are not written correctly or do not interface properly with the System, then memory leaks like the one described above show up. The problem that it creates is a random freeze or crash of an application, often shortly after launch. If the just-launched application requires more memory than is free, then the application will attempt to access what it sees as available RAM. Since the RAM is still technically "staked out" by the extension, a conflict arises. It’s a tough conflict to resolve because, based on the number and size of files that the application has opened, it may or may not attempt to access the "staked-out" RAM. One solution is to add more RAM, but that's a pat answer. If this problem occurs, you may wish to watch the About this Macintosh/Computer window under the Apple menu for these occurrences.

Loose extensions
Loose extensions are ones that sit inside the System Folder but not inside the Extensions folder. Usually, they are placed there by applications and may cause startup problems. Treat these extensions just as you would the ones that exist inside the Extensions folder. They must be moved outside the System Folder to rule them out as troublemakers.

Control panels
After extensions load, control devices are loaded. They also show up on the bottom part of the window as the Mac starts up. They are known more commonly as control panels. Smarter than extensions, these bits of code allow the modification of certain aspects of the Mac. Sound level, monitor resolution, and mouse tracking are examples of control panels. Apple's stock operating system is designed to work flawlessly with the extensions and control panels that are provided. The problems generally occur when third-party control panels are added to the system. They exhibit the same problems as extensions—freezes, crashes, and unexplained errors with applications. When troubleshooting control panels, you should follow the same steps as you do with extensions, turning certain ones on and off to identify the offending control panel.

The Finder
If all extensions and control panels load properly, the Mac will proceed to launch an application called the Finder. This application, located within the System Folder, is launched automatically, with no user input whatsoever. You'll know that the Finder has launched successfully when you see the menu bar and desktop on your Mac. If a freeze or error occurs, it’s probably related to this application.

The first step in attempting to correct this problem is to trash the Finder Preferences, a small file located within the Preferences folder inside the System Folder. Drag this file to the trash and restart the Mac. It often cures the problem by creating a fresh preference set for the Finder. If the problem continues, start up from another device, trash the Finder preferences again, and drag over a backup copy of the Finder application. While there are issues here with some of the boot blocks on the hard drive, that's a discussion for another time.

Startup items
The last items to load are located in the Startup Items Folder inside the System Folder. Some applications will place small files or aliases (read: shortcuts), which launch other applications, in this folder. You can deactivate this folder by holding down the Shift key while you start the Mac.

Error codes
When Macs go awry, they sometimes display dialog boxes with numbers and messages that may indicate what type of error caused the problem. You can ignore these numbers for the most part; however, if you'd like more information about these codes, you can download Mac Error Codes , a document that shows Mac error codes and their reported causes.

The hidden apps
Although we've discussed initial startup to desktop, one more area merits attention. Not all the extensions and control panels are what they seem. In fact, some were applications that now run in the background. Like everything else up to this point, they’re taking up RAM. Since they are indeed applications, they can cause problems for users. Even stock Macs with stock system software have background applications running. The Control Strip control panel, the Folder Actions extension, and the Time Synchronizer extension can be thought of as little applications that run without your knowledge. As you add third-party software, more of these background applications will run and thereby increase the probability of system malfunction.

To see what items are running without your knowledge, download ProcessInfo and run it on your Mac. It shows all the items running in the background and allows you to quit certain items. Knowing what's back there will assist you in your troubleshooting process.

Conclusion
Now that you're aware of the Mac startup sequence, you can troubleshoot problems that arise. Applying this knowledge sometimes requires a small amount of snooping, but in general, most Mac problems can be diagnosed and fixed easily. While all computers have their problems, Macs lend themselves to common-sense fixes more than Windows does. That's another reason why Macs are better. Oh, by the way, I like Indian food.

Schoun Regan is the training and media specialist for Complete Mac Services , an Apple VAR, training, and consulting facility in Louisville, Kentucky that specializes in PC to Mac integration. He teaches throughout North America on a variety of subjects and software. Schoun has been associated with Apple and the Macintosh since 1985 and has authored many Web sites. Certified in several applications and areas, he most enjoys teaching graphics applications.

Schoun's a regularly featured guest on 84Online, a technology-centric radio program heard in more than 30 states including Louisville's Clear Channel station 84 WHAS, and on dot.com, a TV call-in show that’s broadcast from the Louisville area. He resides in the Ohio Valley with his very tolerant wife and children.

The authors and editors have taken care in preparation of the content contained herein but make no expressed or implied warranty of any kind and assume no responsibility for errors or omissions. No liability is assumed for any damages. Always have a verified backup before making any changes.

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