CompuServe Messages

Charles, It all depends on what you want. Without 32 bit RAM the 68020 will run only marginally faster than the super speed 68000 adapter. this is due to the revised (i.e. faster) instructions and if turned on, the instruction cache. Now if you want a 68881 math co-processor, that is a different story. On a 68020 card the 68881 will run 90 to 100 times faster with in-line FFP code. A program has to be specially written and (compliled or assembled) to have in-line FFP code. In Workbench 1.3, CBM is releasing a math library that will detect and use the FFP with any software that uses IEEEMATHLIB.BAS. It has more overhead and will be in the 15-25 times faster range. A 68020 without 32 bit RAM will run 1.3 to 1.8 times faster @ 14.3 Mhz depending on instruction mix. With 32 bit RAM it will run from 2.5 to 4.0 times the speed of the 7.16 Mhz 68000. The 68030 will eventually dominate as it has both an instruction cache and a data cache. It is more efficient going to 32 bit RAM and can operate in burst mode. Best of all it has a built-in memory management unit. The 68851 MMU for the 68020 adds a wait state, and hurts throughput. The 68030 MMU does not add a wait state. The MMU allows neat tricks to get better performance: like a program to move the Kickstart ROM to 32 bit RAM and and access to KS get re-directed to the 32 bit area. With all the gimicks, the 68030 may speed things from 3 to 5.5 times. <continued>