Apple introduced the Mac IIx, which has a 16 MHz 68030 CPU, in September 1988. The 68030 incorporates the memory management unit (MMU), which was a separate chip for the 68020, giving the ‘030 the ability to use virtual memory (VM) with third-party software, although Apple didn’t include VM as part of the Mac OS until System 7 in 1991.
The 68030 can also be used with a newer, more powerful FPU (floating point unit, a.k.a. math coprocessor), the 68882. Overall performance of the 68030 is comparable to the 68020, although the newer chip was eventually available at higher speeds and made its way into the “wicked fast” 40 MHz Mac IIfx – and in a 50 MHz version on some accelerator cards.
The 68030 includes a new memory addressing mode that is one-third faster than on the 68020.
The 25 MHz Mac IIci (Sept. 1989) was the first Mac with a level-2 (L2) cache slot – and also the first faster than 16 MHz and the first with 32-bit “clean” ROMs.
Although the 68030 has two 256-byte caches (twice as much as the 68020), the speed differential between the 25 MHz data bus and 80ns system memory prevents the IIci from achieving its full potential. A relatively small 32 KB L2 cache would boost performance 20-30%. (Larger 64 KB and 128 KB caches were also available, but added so little with a 25 MHz CPU that they didn’t catch on. A 32 KB cache was enough – and Apple eventually made it standard on the IIci. Cache cards use a different kind of memory, static RAM or SRAM, with 25ns or faster performance.)
In addition to Macs, the 68030 was used in some Amiga, Atari ST, and NeXT computers.
Next: Motorola 68040
Summary, 680×0 family
CPU speed* L1 cache FPU** notes 68000 8-16 MHz none none 16-bit data bus, 24-bit addressing 68020 16 MHz 256 bytes 68881 68030 16-40 MHz 2x256 bytes 68882 internal PMMU, supports L2 cache 68LC040 20-25 MHz 2x4096 bytes none can be replaced with 68040 68040 25-40 MHz 2x4096 bytes internal 68060 50-75 MHz 2x8192 bytes internal __________ * as used in Apple computers ** FPU typically used with this CPU
- Great CPUs, past and present, John Bayko. See especially sections on 8080/85, Z-80, 6502, 6809, 680×0, 80×86, ARM (used in Newton), PA-RISC, Sparc, Alpha, PowerPC, and Merced.
- MacTips, RISC, CISC, and Your Mac
- PC Magazine, Motorola and PowerPC (also covers 680×0 series)
- Pipelines, MHz, latency, caches, and more, MacKiDo
Keywords: #motorola68030 #motorolacpus
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