Motorola 68030
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The Motorola 68030 ("sixty-eight-oh-thirty") is a 32-bit microprocessor in Motorola's 68000 family. It was released in 1987. The 68030 was the successor to the Motorola 68020, and was followed by the Motorola 68040. In keeping with general Motorola naming, this CPU is often referred to as the 030 (pronounced oh-three-oh or oh-thirty).
The 68030 features 273,000 transistors with on-chip instruction and data caches of 256 bytes each. It also has an on-chip MMU (memory management unit) but does not have a built in floating-point unit (FPU). The 68881 and the faster 68882 floating point unit chips could be used with the 68030. A lower cost version of the 68030, the Motorola 68EC030, was also released, lacking the on-chip MMU. It was commonly available in both 132 pin QFP and 128 pin PGA packages. The poorer thermal characteristics of the QFP package limited the full 68030 QFP variant to 33 MHz. The PGA 68030s included 40 MHz and 50 MHz versions. There was also a small supply of QFP packaged EC variants.
As a microarchitecture, the 68030 is basically a 68020 core with an additional 256 byte data cache and a process shrink and an added burst mode for the caches, where four longwords can be placed in the cache without further CPU intervention. Motorola used the process shrink to pack more hardware on the die; in this case it was the MMU, which was 68851 compatible. The integration of the MMU made it more cost-effective than the 68020 with an external MMU; it also allowed the 68030 to access memory one cycle faster than a 68020/68851 combo. However, the 68030 can switch between synchronous and asynchronous buses without a reset. The 68030 also lacks some of the 68020's instructions but it lowers power draw by ~25% and increases performance by ~5% compared to 68020.
When used with a 68020 bus, the 68030 did not differentiate itself in performance from the 68020 that it was derived from. However, the 68030 provides an additional synchronous bus interface which, if used, accelerates memory accesses up to 33% compared to an equally clocked 68020. The finer manufacturing process allowed Motorola to scale the full-version processor to 50 MHz. The EC variety topped out at 40 MHz.
The 68030 was used in many models of the Apple Macintosh II and Commodore Amiga series of personal computers, NeXT Cube, Sun Microsystems Sun 3/80 desktop workstation (a member of the "sun3x" architecture, where the earlier "sun3" used a 68020), later Alpha Microsystems multiuser systems, and some descendants of the Atari ST line such as the Atari TT and the Atari Falcon. It was also used in Unix workstations, Laser printers and the Nortel Networks DMS-100 telephone central office switch. More recently, the 68030 core has also been adapted by Freescale into a microcontroller for embedded applications.
Variants
The 68EC030 is a low cost version of the 68030, the difference between the two being that the 68EC030 does not have an on-chip memory management unit (MMU).
The 68EC030 was used as the CPU of one model of the Amiga 4000, and on a number of CPU accelerator cards for the Commodore Amiga line of computers. And in the Cisco Systems 2500 Series router, a small-to-medium enterprise computer internetworking appliance.
The 50 MHz speed is exclusive to the PGA package, PLCC '030s topped at 40 MHz.
Technical data
| Work frequency | 16, 20, 25, 33, 40, 50 MHz, except for MC68EC030 available in 25 and 40 MHz | [1] |
| Internal Harvard architecture | [1] | |
| Address bus | 32 bit | [2] |
| Data bus | 32 bit | [2] |
| Cache | 256 bytes for instruction and data | [1] |
| Dynamic Bus Sizing | [1] | |
| Burst Memory Interface | [1] | |
| Performance | 18 MIPS @ 50 MHz | [1] |
Bibliography
This article is based on material taken from the Free On-line Dictionary of Computing prior to 1 November 2008 and incorporated under the "relicensing" terms of the GFDL, version 1.3 or later.
