What are the most important challenges facing both chip and system designers? How is IBM looking at future development of Power Architecture technology? These are among the issues discussed below by Jim Kahle, an IBM Fellow who has worked since the early 1980s on RISC-based microprocessors. Jim was a founding member of the Somerset Design Center, where he was the project manager for the PowerPC® 603 and follow-on processors leading to the PowerPC G3. He was the chief architect for the POWER4™ core and continually assists in PowerPC roadmap planning.
What are the biggest challenges in developing a new processor architecture?
Jim: Probably the most important challenge today is dealing with power management issues. We are seeing a slowdown in technology's ability to drive performance improvements because power constraints on the chip restrict the availability of the ever-increasing number of transistors for standard uses. Some of the most important design challenges are driven by the power envelope, and in some ways the technology has not kept up. One technique is to reduce voltages aggressively, but the limits of that strategy are being reached. The challenge now is to make designs more efficient, to use on-chip resources more wisely. This is true whether you are designing for portable systems, desktops or servers, stand-alone or in a networked environment with SANs (Storage Area Networks).
Is Moore's Law still in effect? How does it affect the design challenge?
Jim: Moore's Law predicts, and we have seen the production of more and more transistors, and more features are now available -- out-of-order processing, superpipelining, 64-bit architectures among them -- but it is becoming harder to decide how to use those transistors. We have a convergence -- a collision, even -- of the number of transistors and on-chip power constraints. One result of this is to drive the development of multiprocessor architectures to manage that convergence.
How is the role of the processor changing in system design?
Jim: The role of the processor is often dependent on the market segment or application for which the system is destined. Before now, processors tended to have a well-defined, standard role, but with the development of the system-on-chip (SOC) and application-specific systems, the chip designer must understand the whole system and must design the processor as a functional part of an entire system.
How does that translate into a system designer's challenges?
Jim: System designers now have to look at every aspect of the design, including the number of transistors and their available features, size and function of caches. The nature and role of chip architecture changes as part of the entire, or holistic, system design, so they must understand the whole design from chip to final packaging -- its functions and features as well as its constraints.
When designing a processor architecture, where do you look to improve performance?
Jim: We have tapped into a variety of capabilities to improve performance, including superscalar instruction issue, deep pipelining, out-of-order processing, and simultaneous multithreading. Now we are looking more and more at making the total system more efficient and also towards multiprocessor architectures to spread the processing load. IBM came to the forefront in development of high-performance features with the PowerPC architecture. We have been into multithreading since 1996, for example, while some others are just now catching up. With our greater experience in developing advanced features, we can enable system designers to get out in front of the market as well.
Do you think at some point proprietary chip architectures may become a thing of the past?
Jim: Oh, no. There will always be proprietary architectures. Even with the push for openness, some companies will always want their architectures to be closed. IBM is very interested in open standards and participates in many standards organizations, and we contribute, both inside and outside of the company, to technology that will enhance value to our customers. There may be aspects of our architectures that could be opened; at the same time, we can't simply give away vast investments in our intellectual property. We also have to preserve the integrity of our core architectures by maintaining consistent interfaces. IBM Engineering and Technology Services (E&TS) offers design services to our development partners to enable them to interface to and benefit from our advanced technology and experience.
Do you envision the Power Architecture as an industry standard?
Jim: People are already aware of Power [Architecture technology] as a major player in the architectural community. It is becoming stronger and stronger and has much potential for growth, so in many ways it is already a de facto standard. That said, there are no plans to offer Power [Architecture technology] as an industry standard per se, because it would require sacrificing control of a technology that is still evolving. We do intend to extend access to Power Architecture for system development, because there is a greater benefit for IBM and our customers in opening it up than in keeping it closed, in both hardware and software domains.
Is IBM organizing a community of third-party designers to influence future development of Power Architecture technology?
Jim: We announced the Power Architecture community earlier this year and have a network of nearly 2000 individuals that joined the community, downloaded toolkits, or inquired about the direction of Power Architecture. They represent mostly design engineers, from several hundred companies across the spectrum of chip, embedded, and full-system development. We are looking at the Power Architecture community as a basis for a collaborative community to help guide Power Architecture and our architectural development efforts.
Are you presently seeking developer input to the Power Architecture? Where could they participate?
Jim: A processor architecture should be part of a holistic system design, and an open architecture requires lots of customer input. The collaborative nature of an open architecture community is important to determine what a chip architecture should provide. Of course, interface standards are important and must be scrupulously maintained. Where developers can participate most actively is in the infrastructure behind the chips. We invite developers to join the Power Architecture Community to participate in the collaborative innovation of Power Architecture.
Is the Power Everywhere™ initiative linked in any way to IBM's embracing of the open source software movement -- i.e., Linux™?
Jim: There are parallels, if not a direct link. As they evolve, elements of chip architecture must be tied to developments on the software side, where lots of ideas originate from outside. Again, it's collaborative. Hardware and software have to work closely together as a complete, integrated system to reach their highest potential.
Any more thoughts about an open architecture community?
Jim: What is important in starting such a community is that it needs to be a dynamic, collective process. It must respond to the needs of the community itself and also to changes in technology. These needs and changes will guide the evolution of the group itself as well as its work. We will have more to say about plans for an open architecture community in the future.
Learn
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Learn more about Moore's Law at Wikipedia.
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McLaren Harris is a long-time writer and public relations/communications specialist in the computer industry. He can be reached at mclh@comcast.net.
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