The 68LC040 CPU chip has a bug in it which prevents SoftwareFPU from working properly with many FPU applications. Unfortunately there is no work-around for this bug. If you have SoftwareFPU installed on a 68LC040 Macintosh (such as the Centris 610, LC 475 & 575, Performa 475, 476, 575, 577, & 578, PowerBook 520, 540, PowerBook Duo 280, and Quadra 605 and 610), you will have to test each FPU application you use to see whether it will work on your machine. If the application crashes, it is probably due to the 68LC040 CPU chip bug. To verify the cause of the crash, test the same application on a regular 68040 Macintosh. If the application operates correctly on a 68040 Macintosh, the CPU bug is causing the application to crash on your 68LC040 Macintosh. If the application crashes on the 68040 Macintosh, the CPU bug is not the cause of the 68LC040 crash.
Motorola is preparing a revised version of the 68LC040 CPU which supposedly fixes the CPU bug. The new version should be available sometime in fourth quarter 1994. The revised CPU will have a mask revision number of 03E23G or higher. To check the mask revision of the CPU in your Macintosh, open your Macintosh (check to make sure you are not voiding your warranty first), and locate the 68LC040 chip. The mask revision number is printed on the top of the chip, on the second line. The mask revision number reads from left to right, and each series of numeric or alphabetic characters is a different field. Reading left to right, if any of the fields are less than the corresponding field in 03E23G, your CPU has the bug that affects SoftwareFPU. For information on when the revised chip will be incorporated in new 68LC040 Macintoshes, please contact Apple Computer.
If your program crashes because of the 68LC040 CPU bug, your options are: a) replace your FPU application(s) with a version that does not require an FPU, b) replace the 68LC040 CPU chip in your Macintosh with a 68040 CPU, or c) replace your 68LC040 CPU chip with the revised chip (when available).
