Here is my oft posted (but just completely updated) recipe for tuning up a poorly performing Mac:
[the content of this frequently posted article completely updated 5/26/08]
Most folks start to worry that their Mac is slowing down when they notice that boot up is taking longer and/or application launching is taking longer. The tips provided here are intended to speed up these two items. There are other things you can do to speed up your Mac of course, mainly additional RAM and/or faster and larger hard drives, but these topics are not covered here.
Lets start with booting. You may be able to speed up your boot process by understanding the fact that Mac OS X reads and preloads icons for everthing that is in your Documents folder and everything that is on your Desktop. Taking this concept to heart, if you keep a tidy desktop with the smallest number of items possible on it, and minimize the number of files you keep in your Documents folder, you may notice an improvement in boot time. I take this concept to heart myself, keeping only 5 icons on my desktop and keeping all my personal files in a separate "My Documents" folder as opposed to Apple's intended Documents folder. The only things to be found in my Documents folder are items that have been placed there by applications that store configuration information there. Microsoft Office is a notable offender in this regard, storing a hierarchy of folders there.
Still on the topic of booting, make sure that you know what items are being loaded at login of your user account, and eliminate any of them that you don't feel are needed. You will find the list of login items in your System Preferences, Accounts, your_user_id, Login Items.
Now on to hardware settings. Some Macs allow you to control the processor speed and energy consumption. To ensure maximum speed, check that your processor is set for full speed. In Tiger, you can go to Preferences, Energy Saver, Options and look at the drop box down near the bottom called Processor Performance. If it is not set to "Highest", set it to that right away. This maximizes performance, but for notebooks, it may run down the battery faster. Note that not all Macs have this setting - my certainly my PowerMac G5 tower does, but not all Macs do. For Leopard, the preference panel is a bit different in this regard, but poke around and make sure that you are set up for optimum performance, not optimum battery life.
Now lets look at things that consume unncessary amounts of CPU. It is possible you may have some processes running that are consuming a lot of idle CPU, thus slowing down your machine overall. I had a bad widget that did this once. Open Activity Monitor and look at your "resting" CPU occupancy when you are not doing anything in particular with the machine. It should be pretty much zero (maybe 1% to 2% at most). If it not, identify the process or processes that are taking the time. What are they? Do you recognize them? Are they needed? If you find one that is not needed, kill it and see how your machine starts to behave. If this is the cure, you will need to identify the startup item that launches it and delete it.
Still on the "CPU waster" thought, if you have an Intel Mac, it is worth checking for PPC processes - these are running under Rosetta and consume more real time as a result. If there are any routine programs (or Widgets!) of this nature that you are running, you may wish to hunt for a Universal Binary equivalent. To check for PPC processes, fire up Activity Monitor and examine the My Processes display. The processor type (Intel or PPC) is shown in one of the rightmost columns of the My Processes display. If you find any PPC processes there, consider upgrading it a Universal Binary or replacing it with something else.
Next, make sure your Mac is running at peak efficiency by running Mac OS X's routine maintenance scripts. Macs are good, but they require a bit of "care and feeding" just like any other personal computer. My favorite routine maintenance program is the excellent freeware program OnyX. You can use OnyX to run all of the Mac OS X maintenance scripts, as well as clean up a variety of caches and logs. As a bonus, OnyX lets you tinker with a variety to system settings, allowing a degree of personalization of your OS X intall. You can download OnyX from:
http://www.titanium.free.fr/pgs/english.html
Next, you may wish to check that you have enough free space on your hard drive. If your Mac is low on disk space, the file system will start to slow down, and you will notice that as an overall slowdown of the system. Highlight the Macintosh HD icon on your desktop, CTL-click it and select Get Info from the resulting menu. Make sure you have a reasonable amount of space left. If not, a little spring cleaning may be in order (or a larger hard drive!).
There are two excellent apps for showing where all of your hard disk space has gone, Disk Inventory X and WhatSize. Get them at:
Disk Inventory X:
http://www.derlien.com
WhatSize:
http://www.id-design.com/software/whatsize
Both do a great job at letting you zero in on your largest disk space consumers, so that you can hunt down any rogue files (and both are freeware, which is good). If you cannot afford to eliminate any of your files, you may simply need more space. Consider a larger hard drive, or the addition of an external hard drive. If you go for an external hard drive, you can move files off of your system drive and onto it, freeing space on your system drive and thus improving performance.
So, in summary then, take the following steps in order:
1/ Minimize the number of items in your Documents folder and on your desktop.
2/ Ensure that only truly necessary items are loaded as login items
3/ Ensure that your processor speed setting is full (applies to many Macs but not all)
4/ Search for processes that are consuming an unexpected amount of CPU
5/ For Intel Macs, check for PPC processes and potentially prune them out
6/ Do Onyx based full maintenance
7/ Check that you have sufficient available disk space
A final thought. If you routinely leave your web browser running when you are not using it, and have it open at a "busy" page like Mac-Forums, you will find that the Flash-based animated ads on the page consume a ridiculous amount of CPU time. If you want to leave your web browser loaded and running all the time, try pointing it a peaceful page like Google's basic search page - no ads, no unusual CPU consumption. This may help as well.
