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Tweaking Extensions To Boost System Performance

Apple Notes By Mike Watkinson
Published July 2003

Extensions Manager showing extensions viewed as packages, and original system extensions labelled red. Control panels have been labelled green.Extensions Manager showing extensions viewed as packages, and original system extensions labelled red. Control panels have been labelled green.

It's history in OS X, but extension management is a subject every OS 9 user has to deal with. Here, we offer some final advice on the subject and see if tweaking extensions really can boost your system's performance.

Extensions are additions to the core system designed to add functionality and enable and enhance communication with both built-in and third party hardware. Many parts of Mac OS 9 are supplied by Apple as extensions, such as QuickTime, for example, and third-party hardware and software manufacturers provide other extensions to add the necessary functionality for their products. As an example, to use a Lacie Firewire drive, you simply plug it in, and the Mac OS Firewire extension will allow the drive to mount and be formatted with Apple's disc drivers, which wouldn't happen if the extension was absent. Installing the Lacie software adds a Lacie Firewire support extension to augment Apple's own Firewire extension, providing communication between the Lacie disk utility, Silver Lining Pro, and any Firewire discs.

Catching Conflicts

Although extensions don't make permanent changes to the operating system stored on your hard disk, they can cause conflicts with the operating system and with each other when loaded into memory by the OS at start up. Even if you think you've got your extensions co-existing amicably, it's quite possible for an upgrade to either the operating system (if you're not already running the last version of Mac OS 9) or the extension to cause a conflict. Obviously, the default set of extensions supplied with any machine is thoroughly tested before Apple release it, but as soon as you add third-party extensions, or an Apple extension is updated, there's the potential for a conflict.

Apple supply a utility for organising the list of enabled extensions called Extensions Manager, which can be found in the list of Control Panels in the Apple Menu. With a freshly installed system, Extensions Manager will list three sets of extensions under the Selected Set pop-up menu: 'Mac OS All', 'Mac OS Base' and 'My Settings', the name of the unlocked set that's active by default.

If you had the time and patience, a good habit to adopt would be to duplicate the 'My Settings' extension set before each installation, and rename it with the name of the software or hardware you're about to install. This way, every addition to the active extensions list can be tracked, and getting back to a version of the loaded OS plus extensions that operates without the symptoms of extension conflict would be a simple case of choosing the right extension set.

In the real world, however, installations occur without this zealous housekeeping. An extension conflict (which could be between hardware and extension, extension and extension, or extension and OS) could reveal itself gradually, as an emerging pattern of 'soft' crashes (requiring Command/Apple-Alt/Option -Escape-to force-quit the application) or full freezes of the computer, requiring Control- Command/Apple-Power button to restart (newer machines will power down if you hold the power button in for about five seconds).

Using Extensions Manager, choose 'Mac OS Base' or 'Mac OS All' as the extension set and restart. If the problem still occurs, then restart with the Shift key held down. This disables all extensions (disabling them all in Extensions Manager only disables those that EM recognises, but this may also do the trick, since third-party extensions are usually in this group). If your problem still doesn't disappear at this stage, it can't be down to an extension conflict — a fresh install of your OS is then recommended. If the fault does disappear when restarting with a locked set, duplicate and name it. The procedure is then to re-enable extensions in small groups (restarting each time) until the problem reoccurs. This step can be made easier to track and understand if you use the 'View as Packages' option, which shows the extensions grouped according to function and/or install source.

Having found the suspect group (or package) you can narrow your search until you have found the offending extension. If you're lucky, the conflicting extension is not vital to the operation of your system and can simply be disabled. However, if the offending extension is related to the operation of vital software or hardware, there may be an update available on the Internet. Many extensions get updated as a result of reported conflicts arising from hardware/software combinations unforeseen by the manufacturer. If this brings no joy, then contact your supplier and the manufacturer's technical support as to possible fixes, such as suggestions as to which extensions may be in conflict. The ultimate solution would be to abandon that piece of hardware, but it is extremely rare that an extension conflict cannot be resolved.

Third-party Cover

If the method for extension management just described makes wet paint watching sound like the more enticing activity, there are many third-party utilities that can assist and automate the extension-conflict identification process. Perhaps the best known of all third-party extension managers is Casady and Greene's Conflict Catcher (available from, which can find duplicate extensions and is a really good source of information as to the role of each extension.

Extension OverLoad (from allows you to see and control extensions that exist in the Extensions folder but are not visible to Extensions Manager. There are good reasons, however, why Extensions Manager might exhibit this limitation. For example, Text Encoding Converter is not visible to Extensions Manager, but is to Extension Overload. Turning it off, however, will render the System Folder unusable in some versions of the Mac OS. If you wish to delve deeper than Apple's Extension Manager allows, one of these utilities might be worth investigating.

Mac OS 9.1TracksNumber of Stereo PlatinumVerbsNumber of DistortionsMac OS RAM usage
'Mac OS All'4879739.2
'Mac OS Base'47810238.1
Extensions Off4889820.4
Table 1: Test results under Mac OS 9.1.
Mac OS 9.2.2+TracksNumber of Stereo PlatinumVerbsNumber of DistortionsMac OS RAM usage
All Extensions4789846.2
Mac OS All4779839.8
Mac OS Base4779939.4
Extensions Off4869820.9
Table 2: Test results under Mac OS 9.2.2
(with extra extensions added)

Performance Tests

Fine-tuning extension sets is often thought to be one way to achieve higher performance with OS 9, especially for those with older Macs that have limited bandwidth, memory and processing resources. There are countless threads on Internet forums devoted to the ideal extension set for the many combinations of hardware and software, so I decided to test some of the suggestions to see if real gains in performance are achievable.

Using a 333MHz beige G3 Power Mac and Emagic's Logic v4.8.1 as the basis of a typical older system, I tested track and plug-in count under a number of different circumstances. The purpose of trying a low CPU useage plug-in like Distortion was to confirm that the PlatinumVerb results were indeed arbitrarily different and not indicative of any trend (a four-percent change does not indicate a useful performance gain!). To begin with, I installed a new copy of Mac OS 9.1 onto the initialised system disk followed by Logic. My personal experience has proved that this is the most straightforward way to achieve a fast and stable system, since optimising a system already overloaded with unnecessary applications can often be a futile exercise. I tested this configuration with the default 'Mac OS All' and 'Mac OS Base' extension sets, along with no extensions loaded at all (by booting the Mac with the Shift key down). After that, I installed Mac OS 9.2.2 along with a collection of third-party extensions to simulate an overweight system and repeated the same tests, but with the addition of the 'My Settings' set with all the extra extensions enabled.

No amount of extension tweaking can save the author's Power Computing clone, which must now be considered antiquated beyond salvation, and is being pensioned off to email and word-processing duties.No amount of extension tweaking can save the author's Power Computing clone, which must now be considered antiquated beyond salvation, and is being pensioned off to email and word-processing duties.

You can see my test results in Tables 1 and 2 above. From these results, I can safely say that Logic gained nothing significant from adjustments to the extension set in the test system. However, since many people have reported performance and stability gains from extension-set tweaking, I can only presume that I have not successfully recreated the creaking, overweight combination of OS and applications that make up these systems.

If you suspect that you may experience better performance from careful control of the Extension set, running tests similar to those described above will confirm any potential gains. My recommendation would always be to use your computer just for music and to install just the operating system and the required applications, plus the minimum number of additional extensions and system files to support any hardware you've installed. If you're unable (or unwilling) to return the computer to a fresh state by initialising the system disk and reinstalling from scratch, running regular disk maintenance utilities such as Norton Utilities or Alsoft's Disk Warrior is essential.

The test system had plenty of memory, which is essential for the smooth running of most music and audio software, especially since the operating system used about 46MB of memory in the test system, and figures of 70MB are not uncommon with more complicated system configurations. Of course, some older computers require RAM that is now so expensive that it is not justifiable; my Power Computing clone, for example, has been relegated to email and typing duties for just this reason. For quite some time I was under the impression that it had an extension conflict that I could not isolate, which resulted in a system freeze each time Remote Access was launched after the machine had been on for more than 20 minutes. Enabling virtual memory (which I can now do, as it is no longer used for music applications) has cured this problem, serving once again as a gentle reminder that extension conflicts are not the only source of problems!

 Test Spec 
  • Beige G3 tower with 333MHz processor.
  • 384MB of RAM, with Virtual Memory off.
  • Appletalk off.
  • Default Disk cache.
  • Emagic's Logic v4.8.1 assigned 100MB memory.
  • Track-count tests had Logic set to 64 Tracks, Larger Disk Buffer on.
  • Plug-in tests had Logic set to 16 tracks, Larger Process Buffer on.
  • Audio tracks are continuous 16-bit 44.1kHz recordings.
  • All plug-ins are Logic-native, set to stereo.

Extension Tips & Tricks

  • Extension Manager is loaded at boot-up by holding down the spacebar.
  • Most audio software requires the QuickTime extension set (which you can easily see if you View by Packages in Extensions Manager) for features such as importing CD Audio and video playback. However, if you've disabled the networking extensions, the QuickTime Streaming extension will cause an alert at each boot-up unless also disabled.
  • One neat tip I've picked up as a way of being better prepared for future problems after a clear install is to navigate to the Extensions folder in the System Folder, select all the files (hold down Command/Apple and press 'A'), and label them with a colour. This way, any third-party extensions added subsequently are easy to spot since they will appear with a different colour to the original set, and these colours will be visible in Extensions Manager.
  • Mac OS 9 to 9.0.4 contains four Altivec-enabling extensions, which are built into later versions of the operating system and are removed automatically when you update Mac OS to a version greater than 9.0.4.
  • Some versions of Toast had trouble with conflicts between the Toast extension and Apple's Firewire and USB Authoring Support extensions. From Version 5 this has been resolved — Toast now automatically disables these extensions on install.
  • Some USB to SCSI adaptors require extensions that have been reported to cause freezes in Logic. Users of these devices, such as those who connect a legacy SCSI CD writer via such an adaptor, are recommended to set up two extension sets: one for Logic, the other for CD burning.
  • Recycle v2.0 requires the following extensions to be enabled: OpenTransportLib, Open Transport Library, Shared Library Manager, Shared Library Manager PPC; and either Open Tpt AppleTalk Library, Open Tpt Internet Library, or OpenTpt Modem.
  • The Extensions Manger can also be used to disable Control Panels. Steinberg's Nuendo requires both Appletalk and TCP/IP control panels to be switched off in the Extensions Manager (as well as turning off Appletalk in the Chooser).
  • If you spot ObjectSupportLib in your extensions, disable it or, better yet, delete it from the Extensions folder, as it's known to cause instability to Mac OS 8 and disk corruption in Mac OS 9.