System 7: How to Use 32-Bit Addressing

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Article Created: 7 March 1991

Article Change History
08/21/92 - REVISED

  1. To include information on MODE32.


How can I use 32-bit addressing?


To take advantage of 32-bit addressing you must be running System 7. Many Macintosh models can then simply turn on 32-bit addressing in the Memory control panel. Older models in the Macintosh II class may need an additional utility, MODE32 from Connectix and licensed by Apple, to provide the capabilities of 32-bit addressing (Macintosh II, Macintosh IIx, Macintosh IIcx, and Macintosh SE/30; other models like the Plus, SE, and Classic cannot use 32-bit addressing). You would use 32-bit addressing if you had more than 8MB of physical RAM installed in your computer. Alternatively, you can use 32-bit addressing in conjunction with virtual memory to expand your memory to any arbitrary amount up to extent of your hard disk. Remember, however, that Apple recommends that the amount of virtual memory not exceed double the physical memory present in your Macintosh due to the significant performance degradation this will cause.

The Memory Control Panel lets you select between 24-bit operation and 32-bit (addressing) operation. Changes take effect when you restart. When you are running in 32-bit mode, it is important that your applications be 32-bit-compatible. Most current releases of application software are. Check with your software publishers for information about a specific product.

The Macintosh II, IIx, IIcx, and SE/30 models cannot access the benefit of 32-bit addressing without the MODE32 utility, and the Macintosh Plus, SE, and Classic not at all, but 32-bit-compatible software and non-32-bit- compatible software will, of course, work on all of these computers.

Follow these steps to run in 32-bit mode:

  1. Open the Memory Control Panel.
  2. Select 32-bit addressing.
  3. Restart your computer to run in 32-bit mode.

For more information about MODE32, search on MODE32 or Connectix.

Copyright 1991, 1992, Apple Computer, Inc.