More on spikes in Safari processor usage

Over the past week or so, we've been examining possible causes for huge spikes in Safari processor usage. Yesterday we posted a note from Maury McCown that traced the cause to a particular version of NetNewsWire. Since then, we've received several additional emails confirming that installing the latest beta of NetNewsWire fixed the problem.

On the other hand, a few other readers who aren't using NetNewsWire are also experiencing the problem. One possible explanation is that the culprit is not necessarily Safari or NetNewsWire, but a conflict that occurs when two or more applications that use Apple's WebKit, the underlying browser code used by Safari, are running at once. NetNewsWire uses WebKit, as do several other OS X applications.

WebKit is the underlying engine based on KDE that provides essential browsing capabilities to third party applications, and some Apple applications like the revised version of Mail.app to be included with Mac OS X 10.3 (Panther). From Apple's documentation: "Using WebKit, developers can build web browsing features into their applications, including loading URLs, backward and forward navigation, rendering JavaScript, as well as using stylesheets, HTML, DOM, secure access through SSL, and other standard Web protocols and services."

We're not sure why simultaneous access to the WebKit by separate applications would cause this problem. Obviously this problem must be resolved in Panther, or Safari and Mail.app running in conjunction would seemingly cause similar processor spikes.

If you have any additional information on this issue, please drop us a line at late-breakers@macfixit.com.

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