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Open Transport's Limited Compatibility with 680x0

Q: I'm writing an application using the Open Transport native APIs. My original intention was to ship only a 68K version of the application, but I've heard that this will not be compatible with future versions of OT. Is this true?

A: Yes. We strongly recommend that you ship all OT native applications as fat applications. This will give your applications the maximum speed and compatibility.

Under System 7, OT provides OT native APIs for both 68K and PPC clients. This allows 68K OT clients to operate under emulation on PPC Macintoshes. This will not be supported under Copland, because Copland will not support the Apple Shared Library Manager, the dynamic linking technology used by 68K OT clients. Table 1 summarizes this information.

OT Version 68K Client on 68K 68K Client on PPC PPC Client on PPC
OT 1.0.x na (1) Yes (2,3,4) Yes
OT 1.1 Sys 7 Yes Yes Yes
OT 1.5 Sys 7 Yes Yes Yes
OT Copland na (5) No (6) Yes


  1. OT 1.0.x was never shipped or supported on any 68K Macintoshes.
  2. You must link with the OT 1.1b6 or later libraries for this to work.
  3. Obviously you must not call routines that were introduced with OT 1.1
  4. Support for 68K clients on PPC is not well tested under OT 1.0.x. For this and many other reasons, you should emplore your users to upgrade to 1.1.
  5. Copland is a PPC product only.
  6. Copland does not support ASLM, so it is not possible for it to support OT 68K clients.

[Jul 15 1997]

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