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The PowerPC Architecture

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It's not every day a new industry standard comes along. But then, it's not every day three of the world's technology leaders come together to create one.

The PowerPC Alliance marshals the vast financial and technological resources of Apple Computer, IBM, and Motorola to develop leadership products based on a common instruction set architecture and spanning a full spectrum of applications.

Overview of PowerPC: The Next Generation

The initial PowerPC microprocessors were the result of the collaborative efforts of hundreds of engineers from Apple Computer, IBM and Motorola, working in the world's largest joint microprocessor design center, Somerset, in Austin, Texas. Design teams worked in parallel, producing the first four PowerPC microprocessors in just two years, a remarkable feat considering their complexity. Efforts are currently focused on developing new, more powerful PowerPC microprocessors, consistent with the PowerPC architectural guidelines, as well as enhancing the existing family.

From Games to Supercomputers

The PowerPC microprocessor family is broadly scaleable in its uses. For high-performance applications, such as highly parallel supercomputers, members of the PowerPC family contain multiple execution units for symmetrical superscalar operation, cache memory for data and instructions and efficient multiprocessing interface capability. For energy-efficient applications that require both performance and power conversion, such as laptop computers, versions of the PowerPC microprocessor family provide automatic energy conservation modes. Other highly integrated PowerPC microprocessors are versions designed for hand-held, battery-powered applications. From palmtop to multidimensional data analysis, PowerPC microprocessors offer the most scaleable computing solutions available today. Open Standard Provides Unprecedented Design Freedom The PowerPC Architecture is an open standard, not tied to any single operating system, software application package or hardware configuration. This allows design engineers and software programmers unprecedented freedom to create innovative and differentiated new systems for customers and marketplaces.

Powerful, Flexible and Cost Effective

The PowerPC Architecture provides a complete foundation for today's computing applications, with all the necessary building blocks to bring future products to market. Since the architecture is scaleable, it is also a powerful, flexible and cost-effective choice for a variety of embedded control applications.


Computers run software by converting higher-level programming languages into machine-readable code. RISC microprocessors streamline this process. Whereas traditional (complex instruction-set computing, or CISC) processors contain a wide variety of instructions to handle many different tasks, RISC processors contain power those instructions that are used most often. On the rare occasion when a complex instruction is needed, a RISC processor builds it from a combination of basic instructions.

RISC processors are optimized to execute these basic instructions very quickly. The performance gains achieved by speeding up the most-used instructions more than compensate for the time spent "creating" seldom-used complex instructions.

Before the PowerPC microprocessor, RISC technology was used only in systems designed for raw computational power For example, most engineering workstations and commercial database servers use RISC processors. These computers have generally been designed to meet the needs of the UNIX operating system and therefore have been excessively difficult for many PC users to install, learn, use, and maintain.

The PowerPC Alliance believes that RISC technology is the next important technology in personal computing. One important reason is that the performance improvement of successive CISC processors is leveling off, whereas RISC performance is continuing to grow. RISC processors are now being manufactured in high enough volumes to make it cost-effective for the personal computer market.

Why PowerPC?

When the PowerPC Alliance began to look for the microprocessor that could take RISC computing into the next decade, the search was based on specific criteria. After reviewing most of the leading CISC and RISC architectures in the industry, Apple Computer, IBM, and Motorola agreed on PowerPC.

PowerPC offers:

  • A mainstream standard backed by major vendors. With the rapid adoption of the architecture and the anticipated sales of Apple, IBM, Motorola, and others, PowerPC processors have quickly become the most popular RISC processor in the world and a superior alternative to the Intel 80x86 standard.
  • A scaleable architecture that can be used in any type of computer. Until now, RISC microprocessor systems vendors have optimized their products for high-end workstations and server systems. PowerPC microprocessors are the first mainstream RISC microprocessors that can be used in low-cost computers. Developers of PowerPC processors have already created a wide range of system configurations to meet the needs of different types of computer users.
  • Industry-leading technology. The cooperation between Apple, IBM and Motorola brings superior expertise in both microprocessor design and manufacturing to the PowerPC processor effort.
  • Proven high-volume productions. RISC processors today are principally used by specialized workstation vendors. Motorola and IBM have proven their ability to manufacture the millions of microprocessors needed for the personal computer market in addition to supporting lower volumes for specialized markets.
  • Superior development tools. Any new microprocessor architecture needs excellent compilers, debuggers, and other development tools to be successful. Because the Alliance derived PowerPC microprocessors from the POWER architecture already used in IBM's RS/6000 workstations, many compatible development products already exist and are optimized for PowerPC. A number of leading software providers have created PowerPC software development kits for Windows NT, Mac OS, and UNIX, as well as firmware and HAL kits

The alliance of Apple Computer, IBM, and Motorola has produced not just a new RISC architecture, but a new level of performance for computers.

The PowerPC Microprocessor Family

Apple, IBM, and Motorola designed the first four members of the PowerPC microprocessor family simultaneously. Each processor is designed to meet the needs of a different segment of the marketplace.

The PowerPC 601 is the first 32 bit implementation of the PowerPC architecture. It provides high levels of performance for desktop, workstation, and symmetric multiprocessing computer systems and offers design flexibility through operation at either 2.5 volts (601v) or 3.6 volts (601).

The PowerPC 602 microprocessor is a low-power implementation of the PowerPC architecture. It is designed for use in advanced home entertainment and educational devices with audio/video, multimedia, and complex graphics requirements. The PowerPC 602 is also applicable for low-power business and commercial devices with speech recognition and synthesis, wireless communications, and handwriting recognition.

The PowerPC 603 and PowerPC 603e microprocessors, two other low power implementations, offer workstation-level performance packed into a low-cost design. These microprocessors are ideal for desktop computers, notebooks, and entry-level systems. The PowerPC 603 features separate 8-Kbyte physically-addressed instruction and data caches, while the 603e offers 16-Kbyte instruction and data caches.

The PowerPC 604 and PowerPC 604e microprocessors are 32-bit implementations of the PowerPC architecture designed for use in high performance desktop, workstation, and symmetric multiprocessing computer systems. The PowerPC 604 and PowerPC 604e are software and bus compatible with the PowerPC 601, PowerPC 603, and PowerPC 603e microprocessors. The PowerPC 604 features separate 16-Kbyte, physically addressed instruction and data caches, while the 604e offers 32-Kbyte instruction and data caches.

The PowerPC 620 microprocessor is a 64-bit implementation of the PowerPC architecture providing high levels of performance for technical and scientific workstations, application and LAN servers and symmetric multiprocessing computer systems.

The PowerPC Platform Specification

The PowerPC Platform, legally known as the PowerPC Microprocessor Common Hardware Reference Platform, is a set of specifications that define a "unified" personal computer, bringing the combined advantages of the Power Macintosh and the standard PC environment to both system vendors and users. Any computer built to these open standard specifications by any manufacturer will be capable of running a choice of operating systems from Apple, IBM, Microsoft, Novell and SunSoft.

The PowerPC Platform, combined with the superior performance of PowerPC RISC microprocessors, will drive the next generation of applications which address emerging customer requirements to support video, multimedia, virtual reality, speech recognition, 3D graphics and enhanced communications. PowerPC Platform-compliant systems will also benefit from standard industry components which drive system cost down.

The PowerPC Platform, an open reference architecture for the industry which is publicly available, leverages industry standard components. OEMs choosing to implement the PowerPC Platform will benefit not only from the specifications, but also from the reference designs and infrastructure, including chipsets, peripherals and firmware from leading vendors.

Benefits of the PowerPC Platform include:

  • A new level of freedom for computer buyers to purchase systems that can be used with different operating systems for different needs; for example, the graphics design department could use Mac OS, and the accounting department could use OS/2.
  • A new level of freedom for system vendors to build hardware without worrying about which operating system to support. AIX, Mac OS, NetWare, OS/2, Solaris and Windows NT ports are planned for computers built to the PowerPC Platform specifications.
  • A new level of freedom for software designers to harness the superior performance and unique architecture of the PowerPC microprocessor, including its dramatically superior "floating point" capabilities on whichever operating system they chose to support.
  • A new level of application richness and choice for users, as more ISVs rally around the PowerPC standard and write for this single, system-level standard. Given the heavy requirement for "floating point" performance in both the new kinds of applications that will constitute the next generation of computing and the new features in existing applications, the PowerPC Platform will provide a public square for implementing those technologies.
  • A diversity of peripherals and extension cards coming from both the PC and Macintosh worlds using the PCI bus standard which will benefit system vendors, MIS directors and users.

The PowerPC Platform specification delivers on the commitment taken by Apple, IBM and Motorola in November 1994 to create a common system-level architectural standard. The unified standard is flexible and scaleable to support future migration by any manufacturer who chooses to support it. It is also compatible with existing software applications that support either the earlier PowerPC Reference Platform or the Power Macintosh system standard.

PowerPC vs. the Competition

Many tests conducted by independent analysts and press have found that PowerPC-based systems outperform comparably-configured systems using other processors. Even the first-generation PowerPC 601 microprocessor has performance comparable to the leading CISC microprocessor in integer calculations and exceeding it in the floating-point calculations.

Not only do PowerPC microprocessors offer high performance, but they do so in a smaller and cooler package than the competition. Size affects a microprocessor's cost (smaller ones cost less), while heat output affects which models it can be used in (hotter processors need more space and electrical power, which precludes their use in notebook computers).

The size, heat output, and cost of the PowerPC microprocessor are about half those of the leading CISC processor. All of these factors -- combined with its performance -- make the PowerPC a less expensive more versatile foundation for the next generation of personal computers.

Operating System Support

The PowerPC architecture is the first truly open standard for advanced computing. Mindful that computer users tend to be more concerned with the availability of critical application software packages than with the hardware running them, the PowerPC Alliance has set a goal for the PowerPC family to run every major contemporary operating system. Thousands of applications run on these operating systems. Users of PowerPC-based systems can select application packages for everything from word processing to the most complex database management software.

AIX Version 4 for PowerPC

IBM's industrial strength UNIX-based, multithreaded 32-bit operating system lets you tackle even the most demanding business and engineering applications with confidence. The AIX platform also provides an unmatched level of interoperability and scalability for extensive growth options. AIX Version 4 for PowerPC contains all the qualities you expect in a premier server platform and is the basis for new PowerPC and Symmetric MultiProcessing (SMP) systems.

Mac OS

Apple's Mac OS operating system was the first mainstream OS for personal computers to support the PowerPC RISC microprocessor. Today, the Mac OS is used on well over 50% of all PowerPC-based computers. The Mac OS takes advantage of PowerPC to offer the highest performance in personal computing, demonstrated by many independent benchmark studies. The Mac OS provides users the most fulfilling way to get what they want out of their computers by offering the easiest user experience, as well as integrated, leading-edge technologies for graphics, multimedia, communications, and collaboration for customers to implement smart solutions and remain a step ahead. Future versions of the Mac OS will take further advantage of the power of PowerPC to deliver new levels of ease of use and a re-architected foundation for performance and concurrency, that will allow users to work in new and more productive ways than ever before.

OS/2 Warp Connect (PowerPC Edition)

IBM's award-winning OS/2 Warp Connect (PowerPC Edition) is a full-featured, multithreaded, multitasking 32-bit operating system with built-in networking, Internet access and a host of popular programs for word processing, spreadsheets, games and faxing. OS/2 Warp Connect (PowerPC Edition), also supports Netbios, CP/IP and IPX communication over Ethernet, Token Ring and FDDI protocols so you can connect to any kind of LAN, using its resources as if you were locally connected. Best of all, OS/2 Warp Connect gives you everything you need to tap into the riches of the world's networks while also providing what you are looking for most: Ease of use, compatibility, performance and value.

Solaris (PowerPC Edition)

The Solaris operating environment is a powerful and flexible UNIX PowerPC platform. Solaris combines high-performance multitasking, multithreading and multi-user capabilities with industry-leading enterprise network technologies. Solaris provides unlimited, transparent access to systems, servers, printers, remote databases and other resources. Its broad scalability supports virtually any application and configuration needed-for today and in the future.

Windows NT 3.51

Microsoft's newest release of Windows NT includes support for PowerPC-based systems. Windows NT Server 3.51 now includes a tool to help customers manage Client Access Licenses for Microsoft BackOffice products and a utility that enables over-the-network installation of the Windows 95 operating system. Windows NT Workstation 3.51 provides support for Windows 95-compatible applications, popular fax software, a replaceable Winlogon screen and additional devices including PCMCIA.

See Also