With the development of integrated circuits in the 1970s, microprocessors - made from millions of discrete transistors - became the main, programmable control component of computer systems.
With the advances in semiconductor miniaturisation, the microprocessor enabled the development of micro computers, now more familiarly known as the desktop and laptop computers that have revolutionised personal computing.
Microprocessors are traditionally described in terms of their oscillating frequency - 'clock speed' - because they execute one operating instruction per clock cycle. Speed of operation is not the only issue, however, in determining the effectiveness of a chip. Bus speeds and memory latency, for example, are also significant determinants of effective speed and power. Factors such as the size and location of cache memory also play an important factor.
x86 architecture
The de facto architecture for microprocessors is x86. Originally seen in desktop and laptops, it now underpins server systems, courtesy of AMD's Opterons, for example. By contrast, specialised high-end servers will often have proprietary architectures, such as the RISC (reduced instruction set computing)-based processors of Sun servers and the Explicitly Parallel Instruction Computing (EPIC) design for Intel's Itanium 2 systems.
Note that for Intel its Core 2 Duo chips unify the previously separate designs seen for desktop and laptop processors.
Ultra-low voltage designs
As mentioned, some microprocessors are specifically developed for laptops, for example Intel's Centrino range or AMD's Turion systems. These place a premium of power consumption, to increase the battery life of the laptop. More recently, the low-power Intel Atom processors are aimed at 'mobile Internet devices' (MIDs).
The low-voltage or ultra-low voltage designs optimise their use of energy at every possible turn - at an extreme level, even in terms of accessing memory - entering idle states whenever possible.
Multi-processor systems
An increasing trend is towards multi-processor systems. Sometimes this involves packaging separate processors together and sometimes the 'cores' are natively integrated on the same silicon. Intel has favoured the former approach with its Core 2 Duo lineup of processors whereas AMD emphasises the benefits of the latter for its quad-core Opteron-based system codenamed 'Barcelona', which is the first implementation of AMD's K10 microarchitecture.
Multi-core computing is not as straightforward as it may first appear, however. While dual-core systems may see a significant increase in computing power, the number of cores do not always scale so effectively.
The complexity of handling parallel computing is compounded by details of, for example, handling shared cache. AMD has developed a three-level cache system which enables differing levels of access for computing cores sharing the same package.
There is an inherent trade-off in speed of access to localised memory and the benefits of cores being able to share data to complete tasks. The more data a core can keep exclusively to itself, the more effectively it can work, but the less like a multi-core system it becomes. Core management inevitably involves a complex management overhead, eliminating gains in basic computing power.
64-bit computing
Another historical trend for microprocessors is the amount of data they can process with each instruction cycle, whether in terms of data stored in a register or the data communicated along an internal bus. Original microprocessors handled 4-bits as a unit of data. This 'word' size has now increased through 16- and 32-bit computing to the 64-bit systems that are current today.
Essentially, the main advantages of 64-bit systems are twofold. First, by processing larger sets of data in system registers, 64-bit environments are better suited to processor-intensive tasks such as handling 3D graphics. Second, a 64-bit system can support a wider addressable memory range - up from the 4GB addressable by 32-bit systems to 16TB - which benefits data-heavy applications such as databases and business analysis programs.
Process technology
Microprocessors are also increasingly defined by the process technology used to manufacture them - this is the arena where the likes of Intel and IBM fight for competitive advantage. Circuit line widths are now measured in nanometres, rather than microns (1,000 nanometers), with 45nm designs on the near horizon.
Front-end manufacturing refers to the formation of the transistors on the silicon wafers. Techniques and technologies, such as "strained silicon" and "silicon on insulator", can be applied to help improve the performance of the transistors.
The more chips that can be produced from one silicon wafer - which now typically measure 300mm - the greater the output volumes that can be achieved, and the more efficient the manufacturing process.
Codenames
Speaking of 'Barcelona' previously, microprocessors are frequently referred to by codenames adopted by the developer during development.
Intel, for example, named a series of its mobile-oriented processors after towns in the Californian wine growing area, such as Carmel and Nappa. It is common for the industry to talk of a 'Dothan' core, or a 'Prescott'. These will refer to the general microprocessor designs and should not be confused with particular processor model numbers that will adopt one of those designs.
Microprocessors and Chipsets
Traditionally, a microprocessor design involves integration with associated chipsets, which handle more system specific processing requirements.
Sitting between the processor and the southbridge is the northbridge, also known as the memory controller hub. As the name suggests, it is primarily responsible for interfacing with system RAM, as well as passing communications on to the southbridge. This is further away from the CPU and handles less time-critical operations, such as IO, whether for USB connectivity, the PCI bus or other devices.
Moore's Law
Finally, no description of microprocessors would be complete without a reference to the much misquoted Moore's Law. This states that the number of transistors on a chip doubles about every two years. This pushing of technological barriers has shaped the development of processors of ever-increasing power and complexity.
The Intel 4004
It was over 35 years ago, in November 1971, that Intel released its first programmable microprocessor, the Intel 4004, which helped begin the miniaturisation of computing. Although measuring 1/8th by 1/6th of an inch, the chip supplied the same computing power as the ENIAC electronic computer of 1946, which had a room-filling 18,000 vacuum tubes.
The 4004 contained 2,300 transistors, which contrasts with the 291 million transistors of Intel's more recent Core 2 Duo chips. Compared with the current 65nm process technology used for chips, the 4004's circuit line was 10 microns or 10,000 nanometers.
Intel has made datasheets and schematics of the 4004 available under a special non-commercial licence (License of Intel Corporation's 4004 microprocessor historical material).
In the following, we bring together resources from Electronics Weekly to provide more detailed reference information about microprocessors.
ELECTRONICS WEEKLY NEWS ON MICROPROCESSORS
Latest News on Intel
Latest News on AMD
Latest news on VIA
Previous news stories to note
Intel quad-core Nehalem processor breaks record
Intel claims processor performance landmark with first Nehalem quad-core.
Intel builds open source software platform for Atom in Taiwan
Intel has looked to Taiwan as a stage to develop and promote its open-source software plans for the Atom smartphone microprocessor.
Intel brands the Atom
It is goodbye Silverthorne and Diamondville, and hello Atom. This is the brand name chosen by Intel for its previously codenamed family of low-power processors.
Intel, AMD multi-core processing approach doomed - UK multi-processing experts
Intel and AMD will never solve the problems of programming general purpose multi-core processors if they carry on with a shared memory approach, according to UK multi-processing experts.
Intel to reveal two billion transistor chip at ISSCC
Intel will take the wraps off its quad-core Itanium, the first processor to exceed two billion transistors, at the International Solid-State Circuits Conference (ISSCC), to be held on February 3-7 in San Francisco.
Intel unveils its first 45nm Centrino chips
Intel has used CES 2008 to unveil its first Centrino laptop chips built on 45nm process technology.
Intel targets WiMAX with software radio device
Intel has developed a test chip for software defined radio that can handle WiFi, WiMAX and DVB-H digital TV in one chip.
AMD Phenom processor takes HD video mainstream
AMD is delivering its long-awaited Phenom processors - the desktop equivalent of the Barcelona server chips, based on the same native quad-core K10 micro architecture - as its Spider platform takes shape.
Intel goes green with Arizona Fab32 for 45nm 'Penryn' chips
Intel has officially begun production for 45nm desktop, laptop, and servers processors at its manufacturing factory in Chandler, Arizona, dubbed Fab32. This "Penryn" family of processors are expected to launch 12 November.
Quad-Core AMD Opteron processors leave Barcelona
AMD has released its long-awaited native quad-core processor, previously codenamed "Barcelona".
EC charges Intel with three anti-trust offences
The European Commission is charging the microprocessor giant Intel with three anti-trust offences and has given the company ten weeks to respond. Following an oral hearing, a fine could be imposed on the company.
Intel buries hatchet with One Laptop per Child project
Intel has buried the hatchet with the One Laptop per Child (OLPC) initiative and joined forces on the $100 laptop project.
Renesas shows lower cost 45nm process
Renesas Technology has given details of a semiconductor manufacturing technology on a 45nm process for system-on-chip devices and microprocessors at the 2007 Symposium on VLSI Technology being held in Kyoto, Japan.
Intel plans move to 32nm processors
Intel reveals the roadmap for its high-performance Itanium processor family over the coming years.
E2v and Freescale target aerospace with MRAM
E2v is continuing its microprocessor agreement with Freescale Semiconductor and is considering expanding the scope of the deal to include magnetoresistive random access memory (MRAM) products.
Intel offers lead-free processors
Intel is to strengthen its environmental effort by removing lead from all its future processors, beginning with its entire family of 45nm processors.
AMD's technology strategy explained
Phil Hester, CTO of AMD, talks about his company's ecosystem, why it changed its strategy and why Intel is going to be doubly challenged in the future.
Is this the fastest C-programmable processor?
Stream Processors has introduced its highest performance C-programmable processor, which is a 112GMACs (16-bit) or 448GOPS (8-bit) processor.
IBM hails world's fastest microprocessor
IBM claims to have the fastest microprocessor, a 4.7GHz, the dual-core POWER6 processor. It effectively doubles the speed of the previous generation POWER5.
Intel grabs processor market share back from AMD
Intel has reversed recent pressure on its market share by gaining 4.5 per cent in the microprocessor market in the first quarter of 2007, according to a revised estimate from iSuppli.
Comment: Will fast move to 45nm give Intel processor lead?
Will a timely move to 45nm process technology give Intel the next generation of more power efficient microprocessors?
Nallatech designs processor accelerator for Intel
Nallatech has signed an agreement with Intel to develop socket-based microprocessor accelerator modules which support the Intel QuickAssist Technology accelerator strategy.
AMD tops Intel in microprocessor market, says analyst
The showdown between leading chip supplier Intel and rival AMD dominated the semiconductor landscape in 2006, and, according to one market research firm, AMD came out on top.
ELECTRONICS WEEKLY BLOGS ON MICROPROCESSORS
[from Mannerisms]
How Should EC Spend Intel's Gynormous Fine?
What will the EU do with the expected gynormous fine on Intel for flouting anti-trust law in Europe?
Can Intel Ever Succeed Without A Monopoly?
The news from CES 2008 that Intel is to try its hand again at mobile telecoms and consumer chips leads one to ask the question: Can Intel succeed in markets where it doesn't have a monopoly?
Chaos Theory For Semiconductor Forecasting
The difficulties of forecasting the semiconductor industry have prompted analysts Future Horizons to resort to the application of chaos theory...
Rivers, Pubs and Microprocessors
While Intel codenames its processors, during development, after the names of American rivers, PicoChip of Bath goes one better by calling its processors after the names of Bath pubs...
How Powerful Are The Foundries Going To Get?
Just how much power is the foundry industry going to have? Intel says it will ship its first 45nm production microprocessors in the second half of this year. TSMC is saying it will run commercial 45nm wafers in September with...
Intel Being Useful
It's good to see Intel being useful. It was useful in the 1970s in getting MOS memory to work and commercialising microprocessors, the combination of which democratised the computer. Now we all have one...
[from Parallel Lines]
Students use PS3 to run programs on Cell
Students in the Department of Electrical Engineering and Computer Science at the Massachusetts Institute of Technology (MIT) have used a PS3 to study the parallel processing capabilities of the Cell microprocessor.
[from Electro-ramblings]
Intel adopts One Laptop per Child project
First reaction to the news was positive - good to see Intel finally burying its differences with the One Laptop per Child (OLPC) project and throwing its weight behind the venture, but what took it so long?
ELECTRONICS WEEKLY ANALYSIS ON MICROPROCESSORS
Embedded x86: keystone of your non-PC design?
Will multi-core processing fulfil its potential?
CTO interview: Beyond the PC
Exploiting parallelism in processors
AMD's Barcelona: Quad-Core Opteron unveiled
MEMS flex their tiny muscles
Choosing a microcontroller
ELECTRONICS WEEKLY TRENDS & TECHNOLOGIES RELATED TO MICROPROCESSORS
ASICs and ASSPs - www.electronicsweekly.com/asics
MEMS - www.electronicsweekly.com/mems
Semiconductor - www.electronicsweekly.com/semiconductor
Technology Start-ups - www.electronicsweekly.com/startups
ELECTRONICS WEEKLY JOBS INVOLVING MICROPROCESSORS
Careers in the South West & Wales: Home to innovative CMOS chip design
Bristol and its environs have become synonymous as an area for leading edge CMOS chip design.
OTHER RESOURCES
Technology publications with a focus on microprocessors
PC Pro
The Register (Hardware)
The Inquirer
Reference material
Great moments in microprocessor history
The evolution of the modern microprocessor is one of many surprising twists and turns. Who invented the first micro? Who had the first 32-bit single-chip. (IBM)
Intel's Microprocessor Technology Lab
Intel's Microprocessor Technology Labs lead research on microprocessor technologies focusing on those technologies that impact products 5 to 10 years in the future. (Intel)
How Microporcessors Work
In November 1971, Intel introduced the world's first commercial microprocessor, the 4004, invented by three Intel engineers. (Intel)
Understanding the Microprocessor
A series on the basics of microprocessor. (Ars Technica)
What's new in the VLSI Microprocessors
A Guide to High-Performance Microprocessor Resources. (microprocessor.sscc.ru)