Adobe explains why Flash runs so poorly on OS X Lion [Updated]

In a knowledge base article on its website, Adobe offers some reasons why its Flash product doesn’t work so well under Lion, reports TUAW. There are several issues with Flash on Apple’s new OS, but the central one seems to be related to the fact that Flash doesn’t seem to be using hardware acceleration on Lion machines. Updates below.

This results in many upgraders experiencing high fan speeds as the processor, instead of the GPU, is forced to bear the load of Flash computation. MacRumors has isolated some of the important points from the technical article about Flash issues under Lion, but the core issue seems to be related to hardware acceleration.

Flash Player may cause higher CPU activity when playing a YouTube video. Possibly related to disabled hardware acceleration.

So if you’ve been using Flash based sites and your MacBook’s fans have been going at full tilt, now you know why.

Adobe also lists a variety of other issues with Flash under Lion, including the fact that you have to manually upgrade Java now as Apple has discontinued supporting the Java Runtime Environment.

Some other tidbits that OS X Lion users should know:

• Adobe Photoshop CS2 and earlier products use Rosetta and are no longer supported on OS X Lion
• Lion’s reversed scrolling is said to be “opposite of expected”
• Adobe’s products do not support the Restore feature of Lion that puts windows back where they were on restart of apps or the OS
• Adobe’s products do not support Auto Save, Versioning, full-screen mode or some new multitouch gestures

Fllash 10.1, released last year, enabled hardware acceleration for Macs, greatly improving the performance of the web content platform. With those benefits removed in Macs running Lion, the Flash experience is fairly poor.

Update: Adobe has updated its knowledge base article on Flash issues under Lion. The article has a notice added below the note about hardware acceleration. Apparently, Adobe was testing Flash on a developer preview of Lion, not the GM release and had not updated the document.

UPDATE: The final release of Mac OS X Lion (10.7) provides the same support for Flash hardware video acceleration as Mac OS X Snow Leopard (10.6).  The previous “Known Issue” suggesting that video hardware acceleration was disabled in Lion was incorrect and based on tests with a pre-release version of Mac OS X Lion that related to only one particular Mac GPU configuration.  We continue to work closely with Apple to provide Flash Player users with a high quality experience on Mac computers.