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TECHINFO-0020845
TOPIC
Which processor upgrade cards work with Mac OS 7.6?
DISCUSSION
Mac OS 7.6 is not recommended for a 68030-based computer with a 68040 upgrade card installed. If Mac OS 7.6 is installed on a computer with this configuration, it will exhibit problems starting up.
The performance improvements implemented in System 7.5 update 2.0 (7.5.3) specifically for 68030-based computers, can cause cache flushing problems on the 68040 upgrade card when Mac OS 7.6 is installed. There is no workaround to user Mac OS 7.6 with these upgrade cards installed. System 7.5.x users can startup in 24 bit mode with Virtual Memory turned off, turn off the cache of their 68040 cards, and still see benefit from their upgrade card.
Although Apple has not done extensive testing, cards which only increased the speed of an existing processor should work. For example, a 33 MHz 68040 upgrade card in a 25 MHz 68040 computer, or a 33 MHz or 40 MHz 68030 upgrade card in Macintosh IIci class computers. These cards should work correctly with Mac OS 7.6.
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