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Mac OS 8.0 Cache Switch CDEV 7.0

The Cache Switch control panel was provided by Apple Computer to allow users of the Macintosh Quadra series to switch off the cache of their Motorola 68040 processors in case of software incompatibility.


The Cache Switch control panel was first released on October 21, 1991 with System 7.0.1, included with the Macintosh Quadra 700 and 900 computers. The exact same version was included with the system software through Mac OS 8.1 for other 68040-based Macs.


The pipelined cache of the 68040 processors contributed to their dramatic performance improvements, but was also known to break some older hard-coded software. This could be turned off with the Cache Switch for the sake of backward compatibility, but at the expense of a 3-fold penalty in performance.[1][2] This control panel would also work on 3rd-party processor upgrades.


DayStar Digital developed an AutoCache feature for its Turbo 040 that would selectively switch the processor's cache to 68030 mode, depending on software being run, to maintain better compatibility without completely sacrificing performance.[3]


  1. A Pipelined CISC Processor: the 68040 by Leslie S. Smith. 2004.
  2. Cache is King – Enable Yours, HappyMacs. 2013-06-28.
  3. The Legendary DayStar Turbo 040 Hot Rods 68030 Macs by Tyler Sable, Low End Mac. 2005-11-29.