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[MD1] Disabling the CFM-68K Runtime

Apple recommends customers disable the CFM-68K Runtime Enabler extension

Apple Computer has discovered a bug in the CFM-68K Runtime Enabler
extension that can affect the stability of Macintosh computers based on the
680×0 processor. This extension allows the use of certain applications on
680×0 computers, and is installed by an application installer only if the
application requires the extension. Customers will know they have this
extension installed if the file ” CFM-68K Runtime Enabler” (note that the
file name begins with a space) is located in their Extensions folder which
resides inside their System folder.

In certain circumstances, the bug can cause applications which rely on the
CFM-68K Runtime Enabler to not function properly, resulting in application
instability and potential loss of data. The most obvious symptoms are what
appear to be random system crashes and hangs. Macintosh and Mac
OS-compatible computers based on the PowerPC processor are not affected by
this bug.

Because of the potential quality impact of this bug, Apple is recommending
that customers with computers based on the 680×0 processor disable the
CFM-68K Runtime Enabler extension and not use programs which rely on this
extension. See below for instructions on how to disable this extension.
Apple is currently working to resolve this bug.

What is the CFM-68K Runtime Enabler?

The CFM-68K Runtime Enabler is an extension which makes it easier for
developers of applications to design their programs to run on both 680×0
and PowerPC computers without having to write separate programs for both
processor families.

On a more technical level, the Code Fragment Manager (“CFM”) was originally
introduced by Apple only for Macintosh and Mac OS-compatible computers
based on the PowerPC processor. It allows applications to share their
programming code through special files known as shared libraries. In
addition to being able to share programming code, applications which are
programmed to use shared libraries can reduce their memory requirements. In
response to the success of the PowerPC version of CFM, Apple introduced a
version of CFM for Macintosh computers based on the 680×0 processor. This
version of CFM for 680×0-based Macintosh computers is the CFM-68K Runtime
Enabler extension.

What applications are affected by this bug?

Only applications which have been explicitly programmed to use the CFM-68K
Runtime Enabler can be affected by this bug. Apple Computer products which
rely on CFM-68K Runtime Enabler are: OpenDoc, Cyberdog, LaserWriter
(versions 8.4 and 8.4.1 only), and the Apple Media Tool. Only the 68k
versions of these software packages are affected. This bug does not affect
PowerPC versions of these products. There are currently few applications
which rely on the CFM-68K Runtime Enabler and therefore Apple does not
believe that this problem is very widespread.

You can identify applications which rely on the CFM-68K Runtime Enabler
extension once the extension is disabled (see below for instructions on
disabling the extension). When the CFM-68K Runtime Enabler is disabled,
applications which rely on it will report the following error when you
attempt to launch them:

*

Is this bug caused by these applications?

Not directly. The bug is caused by the use of CFM-68K Runtime Enabler in
ways it was not designed to handle. Unfortunately, its limitations were not
recognized by the applications.

What should I do if I have installed one of these affected products?

If you have installed OpenDoc or Cyberdog, you should not use these
products until Apple releases a solution for this problem. If you have
installed LaserWriter version 8.4 or 8.4.1, you should install LaserWriter
version 8.3.4, which does not rely on the CFM-68K Runtime Enabler. If you
do not have LaserWriter 8.3.4, you can download it from the Apple support
site on the World Wide Web, which is located at:

http://www.info.apple.com/

If you are a member of the Apple Media Tool developer community, please
visit the AMT web site at http://amt.apple.com/ for more information.

If you have a PowerPC-based Macintosh or Mac OS-compatible computer, your
computer is not affected by this problem. Therefore, you can continue to
use these products.

Should I contact third-party application developers about this problem?

No. Since a fix for this problem will be accomplished by modifying Apple’s
CFM-68K Runtime Enabler, third-party application developers will be unable
to assist you with this problem.

How do I disable this extension?

There are two ways to disable this extension. One is to drag the extension
out of the Extensions folder which resides in your System Folder. The other
is to use the Extensions Manager control panel.

To disable the CFM-68K Runtime Enabler extension using the Extensions
Manager control panel, perform the following steps:

1. Open the Apple menu item and select Control Panels.

2. Locate Extensions Manager and double click it to open it.

3. Locate ” CFM-68K Runtime Enabler”. Note that there is a space at the
beginning of the name. You should find this extension near the top of the
Extensions Manager window under the Extensions heading, similar to this:

*

4. If there is a check mark (“”) next to CFM-68K Runtime Enabler, click on
it so that there is no check mark.

5. Close the Extensions Manager window.

6. Restart your computer.

Is this bug caused by recent changes in the CFM68k Runtime Enabler?

No. This bug exists in all currently shipping versions of CFM-68K Runtime
Enabler, but was found during recent testing.

Why has it taken Apple this long to identify this bug?

Only recently have applications begun to make use of the CFM-68K Runtime
Enabler extension. The conditions which cause this bug have only been
exposed by recent increased use of the extension by applications.

I have a PowerPC computer. Does this affect me?

No. The bug is only in the CFM-68K Runtime Enabler extension, which runs
only on Macintosh computers based on the 680×0 processor. The Mac OS on
PowerPC computers does have code fragment capabilities, but it is
accomplished through different programming techniques not affected by this
bug.

What is Apple doing to fix this bug?

Apple has assigned a team of engineers to develop a solution for the bug.
At this time, there is not enough information to make any statements about
delivery of a solution.

How can I get the technical details about this bug?

Apple has a Technote about this bug available on the World Wide Web at:

http://devworld.apple.com/dev/technotes/tn/tn1084.html

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