At a Glance

Expert's Rating

Pros

Cons

Recently, my MacBook Pro has been doing this thing where the fan suddenly revs up for no apparent reason. I’m not rendering HD video, ripping a movie from a DVD, or playing World of Warcraft, which can really get the fans spinning. All I’m doing is something like working in Pages—as I am now as I write this article—with Mail, Adium, and Twitterific also open. But that’s it, and my MacBook Pro still sounds like a 747 ready for take off.

To see what’s going on under the hood of my MacBook Pro, I installed iSlayer’s free iStat menus 1.3, a set of hardware monitoring tools for your menu bar. The software won’t diagnose what’s wrong with my MacBook Pro (if there’s anything wrong with it in the first place), but it can give me more information about what my MacBook Pro is doing, letting me try to isolate the problem and fix it.

After installing iStat menus, a new pane in System Preferences lets you configure the software’s eight system monitoring tools:

CPU: Shows you what processes your CPUs are performing.
Memory: Lets you monitors memory usage.
Drives: Indicates available disk space and read/write data rates.
Network: Displays network bandwidth and usage (incoming and outbound). Also monitors Bluetooth traffic.
Temps: Lets you watch the temperature of your Mac’s components, such as its CPU, GPU, memory, and hard drive.
Fans & Power: Indicates rotation rates of your Mac’s fans. Also shows voltages and power usage (although not the remaining power in a laptop battery).
Bluetooth: Provides the same functionality as Mac OS X’s Bluetooth menu extra, as well as a display of the battery level of your Apple wireless keyboard.
Date & Time: Offers some expanded features not found in the standard Date & Time menu display.

You can turn on all of these menus, or you can pick and choose. The Date & Time, Network, and Bluetooth menus essentially replace Mac OS X’s Date & Time, AirPort, and Bluetooth menus, respectively, but even so, if you use iStat menus other menus, the menu bar gets cluttered really fast. And if you like using the translucent OS X menu bar, you might not be pleased with the appearance.

iStat menus with a translucent menu bar — iStat menu with translucent menu bar.

iSlayer also makes a Dashboard widget, iStat Pro, that performs many of the same tasks as iStat menus, but I like iStat menus because I can instantly look up at my menu bar and see what’s happening. For example, when my MacBook Pro’s fans start to rev up, I can glance at the corner of my screen and to see if the processors are experiencing a heavy load or if there’s any unexpected network traffic or hard drive activity.

Click on an iStat menus menu item and you get more information. For example, the CPU menu shows how much effort your CPU cores are dedicating to each task at hand. The Memory menu tells you how your Mac’s memory is being allocated. The Date & Time menu is one of my favorites: click on it, and you see a calendar of the current month, with a menu selection that lets you launch iCal. (The data displayed when you click on the Drives, Temps, and Network menus is noted in the bulleted list, above.)

iStat menu CPU — The CPU iStat menu monitor displays CPU information that’s similar to that found in the Activity Monitor utility. In fact, you can launch Activity Monitor from within the CPU iStat menu.

iStat menus preferences — iStat menus can be customized to suit your tastes.

iStat menus lets you adjust the text and graph colors; you can also adjust the text size for some menu items (Fans & Power, Temps, and Date & Time). Curiously, the CPU and Memory menus show a dimmed text size menu, so I wasn’t able to adjust the text size. The menus that appear when you click on an iStat menu have a black background and white text—unfortunately, you can’t change this to colors you find more pleasing.

You can also adjust how frequently iStat menus updates its information. When I set it to check at different intervals, I didn’t notice any lag or other effects on my overall performance; as far as I could tell, iStat menus doesn’t noticeably degrade performance. (One option I would like to see is the ability to reset iStat menus to its default settings.)

iStat menus is a good way to find out what’s going on under the hood of your Mac. Those who don’t like how it crowds your menu bar can try iStat Pro, but if you want to have instant access to system activity data, iStat menu works well.

iStat menu requires Mac OS 10.4 or later.

[Roman Loyola is a Macworld senior editor.]