Introduction to Today’s Microprocessor trends
From their humble beginning 25 years ago, microprocessors have proliferated into an astounding range of chips, powering devices ranging from telephones to supercomputers. Today, microprocessors for personal computers get widespread attention--and have enabled Intel to become the world's largest semiconductor maker. In addition, embedded microprocessors are at the heart of a diverse range of devices that have become staples of affluent consumers worldwide.
MAJC (pronounced "magic") is an acronym for "Microprocessor Architecture for Java Computing." MAJC is a microprocessor architecture designed to meet the broadband demands of the 21st century. Addressing the challenge of high bandwidth and the need for state-of-the-art computational performance, MAJC architecture is characterized by:
• Scalability to take full advantage of advances in semiconductor technology.
. Broad scalabilty to systems with large numbers of processors.
• A new standard of performance for applications with DSP or New Media computational needs.
• Focus on bandwidth throughput.
Processor Needs into the 21st Century
Several microprocessor trends were identified and accommodated in the design of the MAJC Architecture:
• Convergence of communication media and computers (audio, video, and data) require processors to compute information at wire speed.
• Advancements in semiconductor technology will provide rapidly-increasing resources on each microprocessor chip.
• As microprocessors are used in increasingly disparate applications from smart cards to supercomputers there is great value in the ability to create a wide span of implementations from a given processor architecture.
• Software, over time, will become independent of specific instruction sets; Just-In-Time (JIT) compilation techniques are expected to predominate for general-purpose processors and eliminate binary compatibility issues.
• Bandwidth between processors, memory, and I/O devices needs to be available to move information in real-time.
• The content processed by computers is becoming increasingly media-rich; DSP-like functions are required to process this media content.
Features of Today’s Microprocessors.
• Modular Architecture
To support the creation of a wide range of implementations the architecture supports modular implementations. A basic implementation might comprise a single processor unit with four functional units. By replicating those design elements, an implementation can be built that includes a few or even hundreds of processors, each with four functional units, each of which can operate on many data items simultaneously with parallel-operation (SIMD) instructions. Conversely, a tiny application-specific implementation can be derived from the basic one by trimming the complement of functional units down to one or two and/or removing hardware support for any instructions not needed in its target application.
• Multiple Processor Units per Cluster
Although a MAJC implementation can be a single processor unit, the architecture explicitly incorporates the concept of multiple processors per implementation. Given 21st century semiconductor density, each such array of processor units or "processor cluster" can be implemented on a single chip. As semiconductor technology advances, clusters with more processors per chip can be implemented.
• Multiple Functional Units per Processor Unit
Every MAJC processor unit can issue multiple instructions simultaneously, one to each of its functional units. Most implementations are expected to provide two to four functional units per processor unit.
A Brief History of the Pentium Processor Family
The Pentium family of processors, which has its roots in the Intel486(TM) processor, uses the Intel486 instruction set (with a few additional instructions). The term ''Pentium processor'' refers to a family of microprocessors that share a common architecture and instruction set. The first Pentium processors (the P5 variety) were introduced in 1993. This 5.0-V processor was fabricated in 0.8-micron bipolar complementary metal oxide semiconductor (BiCMOS) technology. The P5 processor runs at a clock frequency of either 60 or 66 MHz and has 3.1 million transistors.
The next version of the Pentium processor family, the P54C processor, was introduced in 1994. The P54C processors are fabricated in 3.3-V, 0.6-micron BiCMOS technology. The P54C processor also has System Management Mode (SMM) for advanced power management
The Intel Pentium processor, like its predecessor the Intel486 microprocessor, is fully software compatible with the installed base of over 100 million compatible Intel architecture systems. In addition, the Intel Pentium processor provides new levels of performance to new and existing software through a reimplementation of the Intel 32-bit instruction set architecture using the latest, most advanced, design techniques. Optimized, dual execution units provide one-clock execution for "core" instructions, while advanced technology, such as superscalar architecture, branch prediction, and execution pipelining, enables multiple instructions to execute in parallel with high efficiency. Separate code and data caches combined with wide 128-bit and 256-bit internal data paths and a 64-bit, burstable, external bus allow these performance levels to be sustained in cost-effective systems. The application of this advanced technology in the Intel Pentium processor brings "state of the art" performance and capability to existing Intel architecture software as well as new and advanced applications.
The Pentium processor has two primary operating modes and a "system management mode."
The operating mode determines which instructions and architectural features are accessible.
These modes are:
• Protected Mode
This is the native state of the microprocessor. In this mode all instructions and architectural features are available, providing the highest performance and capability. This is the recommended mode that all new applications and operating systems should
target. Among the capabilities of protected mode is the ability to directly execute "real-address mode" 8086 software in a protected, multi-tasking environment. This feature is known as Virtual-8086 "mode" (or "V86 mode"). Virtual-8086 "mode" however, is not actually a processor "mode," it is in fact an attribute which can be enabled for any task (with
Advanced Features
The Pentium P54C processor is the product of a marriage between the Pentium processor's architecture and Intel's 0.6-micron, 3.3-V BiCMOS process The Pentium processor achieves higher performance than the fastest Intel486 processor by making use of the following advanced technologies.
• Superscalar Execution: The Intel486 processor can execute only one instruction at a time. With superscalar execution, the Pentium processor can sometimes execute two instructions simultaneously.
• Branch Target Buffer: The Pentium processor fetches the branch target instruction before it executes the branch instruction.
• 64-Bit Bus: With its 64-bit-wide external data bus (in contrast to the Intel486 processor's 32-bit- wide external bus) the Pentium processor can handle up to twice the data load of the Intel486 processor at the same clock frequency.
• Instruction Optimization: The Pentium processor has been optimized to run critical instructions in fewer clock cycles than the Intel486 processor.
• Floating-Point Optimization: The Pentium processor executes individual instructions faster through execution pipelining, which allows multiple floating-point instructions to be executed at the same time.
• Pentium Extensions: The Pentium processor has fewer instruction set extensions than the Intel486 processors. The Pentium processor also has a set of extensions for multiprocessor (MP) operation. This makes a computer with multiple Pentium processors possible.
A Pentium system, with its wide, fast buses, advanced write-back cache/memory subsystem, and powerful processor, will deliver more power for today's software applications, and also optimize the performance of advanced 32-bit operating systems (such as Windows 95) and 32-bit software applications.
