CompuServe Messages

Lee, The differences between the 68030 and 68020 are more than just the built-in MMU. The 68020 has only a 256 byte instruction cache, whereas the 68030 has both a 256 byte instruction cache and data cache. The caches permit the processor to work with instructions and data held within the CPU rather than fetching it from main memory, which speeds up processing dramatically. However, the bulk of the improvement is contributed by the instruction cache, which both CPUs have. The MMU has limited use on the Amiga currently. Mainly it can be used to copy the DOS ROM image into 32 bit RAM (if you have any) which further enhances speed, particularly for anything using ROM calls. Inasmuch as most graphic primitives are in ROM, it helps speed up graphic operations substantially. Your computer does NOT have an MMU. Either the accelerator card has it or you are without. Perhaps in the future a later version of the OS may implement virtual memory, which would need an MMU, but right now there is little need for it except as I mentioned previously. The enhancements of an accelerator card will be further benefited by having 32 bit RAM. You can expect to spend an additional $400 or so for a RAM card for the MegaMidget with 2 meg of RAM and about $600 for 4 meg. This is in addition to the accelerator. If you buy a card with RAM included, such as the GVP cards, you can expect to pay about what a MegaMidget with the RAM card will cost. If you would like a cheap alternative, I have an older Hurricane 68020 card with 4 Meg of 32 bit RAM and 68881 FPU (operates at 14 Mhz) for $500.