МИНИСТЕРСТВО ОБРАЗОВАНИЯ И НАУКИ

РОССИЙСКОЙ ФЕДЕРАЦИИ

Государственное образовательное учреждение

высшего профессионального образования

«Пермский государственный университет»

Кафедра английского языка профессиональной коммуникации

Английский язык

English Reader for Computer Science Students

Методическая разработка

Часть 4

1. Составитель Бабаджан Сергей Савельевич

Английский язык . English Reader for Computer Science

Students/ метод. разработка /сост. С.С, Бабаджан;

. Перм. гос. ун-т. – Пермь, 2011.-Ч.4 -52с.

Данная разработка предназначена для студентов специальностей «Радиофизика» и ПМИ среднего и продвинутого уровней и может быть также использована при работе с аспирантами .

Издается по решению методической комиссии факультета современных иностранных языков и литератур Пермского государственного университета.

1. Transmetamorphosis

Silicon Valley’s most mysterious company has revealed its revolutionary new microchip at last. What is all the fuss about?

Computer technology

Search

archive

IT WAS not a time machine, nor a cure for cancer, nor an antigravity device. Instead, the new product unveiled on January 19^th by Transmeta, a notoriously secretive firm based in Santa Clara, California, turned out to be a new kind of microchip. After months of speculation and build-up, this came as an anti-climax to some. But for geeks around the world, who have spent the past few days poring over the chip’s technical details and discussing it on the Internet, Transmeta did not disappoint.

Its design takes a number of computing tricks and combines them in an entirely novel way. The immediate benefit, and the one Transmeta is emphasising with its first two products, is a microprocessor that can run software written for Intel’s chips, while consuming a fraction of the power.

Big deal, you might think. But Transmeta’s core technology does a lot more than just allow laptop computers to run all day on a single charge. Its chips operate in a fundamentally new way, allowing them to emulate (and hence run software designed for) any existing microprocessor, without the loss of performance normally associated with such emulation. Its technology also side-steps several thorny problems in the design of microprocessors. Whatever happens to Transmeta’s products in the marketplace, its radical approach looks likely to have a profound influence on the future course of the industry.

1. Thinking caps on

To understand what is so clever about Transmeta’s idea, it is necessary to recall how today’s chips work. A programmer writes a piece of software in a “high-level” language (such as C++). This program is then fed into a second piece of software called a compiler, which translates it into a sequence of machine instructions for a specific kind of microprocessor, such as Intel’s x86 family, which can then run the original program.

So far, so good. As they devise new chips, however, designers face a problem. On the one hand, they want the new chips to run as fast as possible. On the other they want them to be “backward-compatible”—able, in other words, to cope with software compiled for previous chips. In recent years, Intel and others have squared this circle by using clever hardware on their chips to analyse sequences of instructions before executing them, and then employing various tricks to speed things up.

One of these tricks involves splitting a sequence of instructions into several separate sub-sequences and executing these in parallel. Provided the sub-sequences do not interfere with each other, the result is faster execution. Another trick, called “out of order” execution, involves re-ordering instructions where possible to make things run faster. More advanced still is a technique called “speculation”, where the chip foresees a branch in the program, calculates both possible results in advance, and then throws away the incorrect answer and uses the correct one when the branch is reached.

To overcome the problem of backward-compatibility, modern x86 chips such as the Pentium are able to take x86-style instructions from old software and split them up into several smaller micro-operations which lend themselves better to performance-enhancing trickery. As a result, microprocessors have continued to improve in performance over the past few years. But there is a price to pay: millions of transistors are needed to pull these tricks off. This makes modern x86 chips large and power-hungry, which is bad news for users of portable computers. Intel’s latest “mobile” Pentium III chips—intended specifically for such portables—consume around 20 watts.

Transmeta’s approach seems, in contrast, so simple that it is surprising that nobody thought of it before. Instead of building an even more complicated x86-compatible processor, the firm has created an entirely new chip of its own that is specifically designed to execute micro-ops quickly and efficiently. The translation of x86 instructions into micro-ops, along with the analysis, re-ordering, speculation and so on are then done by a special layer of “code-morphing” software that sits between the chip and the x86 program, thus fooling the program into thinking that it is running on a standard x86-compatible processor.

The advantage of doing this translation and manipulation in software, rather than in hardware, is that far more complex kinds of optimisation are possible. For example, once the code-morphing software has translated a particular chunk of x86 code into micro-ops it can store the translated chunk in a special memory to avoid having to translate it again. Chips that do the translation in hardware have to re-translate the same instructions over and over.

More important, the Transmeta chip is able to maintain statistics about which parts of the program it is running are executed most often. Once the code-morphing software has identified a chunk of x86 code that has a high “repeat rate”, it will then re-examine that chunk to see if it can be optimised even further. This additional optimisation takes extra time, but the fact that the code will subsequently run faster more than makes up for it. The result is that the execution of a particular program accelerates as the microprocessor tunes itself to run the software as efficiently as possible—something that would be a nightmare to do in hardware alone.

Splitting the operation of the chip into hardware and software components has other advantages. Transmeta’s chips can be rejigged to emulate any microprocessor, or more than one at once. The firm will also be able to redesign the hardware altogether to take advantage of new technologies as they appear, rewriting the code-morphing software to maintain compatibility. (The two chips introduced last week are, in fact, based on completely different hardware designs from one another.)

The immediate benefit of all this trickery is to reduce power consumption. And consumption is further reduced by adjusting the operating speed and voltage of the chip on the fly, depending on the user’s activity. A 10% reduction in processor speed, for example, results in a 30% drop in the power required. The result is that Transmeta’s Crusoe TM5400 chip, which is intended for use in laptop computers, has a performance comparable with a mobile Pentium III, but contains a quarter of the number of logic transistors and consumes a twentieth of the power.

This explains why Transmeta is, initially at least, aiming its products at the portable-computer market. Diamond Multimedia, a consumer-electronics firm, has already announced plans to build tablet-like web-browsing devices using Crusoe chips. Taiwanese computer manufacturers Acer, Quanta and Uniwell are thought to be interested in building ultra-light laptop computers with them. The first Crusoe-powered laptops are expected to appear later this year.

By choosing to concentrate on the niche market for chips for portable computers rather than attacking the desktop market directly, Transmeta has so far declined to take on Intel on its home ground. But Dave Ditzel, the company’s founder and a pioneer of “reduced instruction set computing” (RISC), a previous breakthrough in microprocessor design, points out that ultra-light laptops are the fastest-growing part of the PC market, and that mobile Internet-access devices are expected rapidly to become a multi-billion dollar business. As he says, “that’s a nice niche”. Ultimately, however, the self-tuning nature of the Transmeta chip design could offer advantages in desktop machines and high-performance servers as well portables. It will be interesting to see what follows in Crusoe’s footsteps.