Athlon XP versus Pentium 4

The Athlon processor came in various versions. It started as a Slot A module (see Fig. 107 on page 42). It was then moved to Socket A, when the L2 cache was integrated.

In 2001, a new Athlon XP version was released, which included improvements like a new Hardware Auto Data Prefetch Unit and a bigger Translation Look-aside Buffer. The Athlon XP was much less advanced than the Pentium 4 but quite superior at clock frequencies less than 2000 MHz. A 1667 MHz version of AthlonXP was sold as 2000+. This indicates, that the processor as a minimum performs like a 2000 MHz Pentium 4.

Later we saw Athlons in other versions. The latest was based on a new kernel called ”Barton”. It was introduced in 2003 with a L2-cachen of 512 KB. AMD tried to sell the 2166 MHz version under the brand 3000+. It did not work. A Pentium 4 running at 3000 MHz had no problems outperforming the Athlon.

Athlon

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The last processor I will discuss is the popular Athlon and Athlon 64 processor series (or K7 and K8).

It was a big effort on the part of the relatively small manufacturer, AMD, when they challenged the giant Intel with a complete new processor design.

The first models were released in 1999, at a time when Intel was the completely dominant supplier of PC processors. AMD set their sights high – they wanted to make a better processor than the Pentium II, and yet cheaper at the same time. There was a fierce battle between AMD and Intel between 1999 and 2001, and one would have to say that AMD was the victor. They certainly took a large part of the market from Intel.

The original 1999 Athlon was very powerfully equipped with pipelines and computing units:

1. Three instruction decoders which translated X86 program CISC instructions into the more efficient RISC instructions (ROP’s) – 9 of which could be executed at the same time.

2. Could handle up to 72 instructions (ROP out of order) at the same time (the Pentium III could manage 40, the K6-2 only 24).

3. Very strong FPU performance, with three simultaneous instructions.

All in all, the Athlon was in a class above the Pentium II and III in those years. Since Athlon processors were sold at competitive prices, they were incredibly successful. They also launched the Duron line of processors, as the counterpart to Intel’s Celeron, and were just as successful with it.

Evolution of the Pentium 4

As was mentioned earlier, the older P6 architecture was released back in 1995. Up to 2002, the Pentium III processors were sold alongside the Pentium 4. That means, in practise, that Intel’s sixth CPU generation has lasted 7 years.

Similarly, we may expect this seventh generation Pentium 4 to dominate the market for a number of years. The processors may still be called Pentium 4, but it comes in al lot varietes.

A mayor modification comes with the version using 0.65 micron process technology. It will open for higher clock frequencies, but there will also be a number of other improvements.

Hyper-Threading Technology is a very exciting structure, which can be briefly outlined as follows: In order to exploit the powerful pipeline in the Pentium 4, it has been permitted to process two threads at the same time. Threads are series of software instructions. Normal processors can only process one thread at a time.

In servers, where several processors are installed in the same motherboard (MP systems), several threads can be processed at the same time. However, this requires that the programs be set up to exploit the MP system, as discussed on page 31.

The new thing is that a single Pentium 4 logically can function as if there physically were two processors in the pc. The processor core (with its long pipelines) is simply so powerful that it can, in many cases, act as two processors. It’s a bit like one person being able to carry on two independent telephone conversations at the same time.


Figur 110. The Pentium 4 is ready for MP functions.

Hyper-Threading works very well in Intel’s Prescott-versions of Pentium 4. You gain performance when you operate more than one task at the time. If you have two programs working simultaneously, both putting heavy pressure on the CPU, you will benefit from this technology. But you need a MP-compatible operating system (like Windows XP Professional) to benefit from it.

The next step in this evolution is the production of dual-core processors. AMD produces Opteron chips which hold two processors in one chip. Intel is working on dual core versions of the Pentium 4 (with the codename ”Smithfield”). These chips will find use in servers and high performance pc’s. A dual core Pentium 4 with Hyper-Threading enabled will in fact operate as a virtual quad-core processor.


Figur 111. A dual core processor with Hyper Threading operates as virtual quad-processor.

Intel also produces EE-versions of the Pentium 4. EE is for Extreme Edition, and these processors are extremely speedy versions carrying 2 MB of L2 cache.

In late 2004 Intel changed the socket design of the Pentium 4. The new processors have no ”pins”; they connect directly to the socket using little contacts in the processor surface.



Figur 112. The LGA 775 socket for Pentium 4.

DDR RAM

It is expensive to produce fast RAM chips. So someone hit on a smart trick in 1999-2000, which in one blow made normal RAM twice as fast. That was the beginning of DDR RAM (Double Data Rate). See the module in Fig. 131.

In DDR RAM, the clock signal is used twice. Data is transferred both when the signal rises, and when it falls. This makes it possible to perform twice as many operations per clock pulse, compared to earlier RAM.

SDRAM

The big qualitative shift came in around 1997, when SDRAM (Synchronous DRAM) began to break in. This is a completely new technology, which of course required new chipsets. SDRAM, in contrast to the earlier types of RAM, operates synchronously with the system bus.

Data can (in burst mode) be fetched on every clock pulse. Thus the module can operate fully synchronised with (at the same beat as) the bus – without so-called wait states (inactive clock pulses). Because they are linked synchronously to the system bus, SDRAM modules can run at much higher clock frequencies.

The 100 MHz SDRAM (PC100) quickly became popular, and with new processors and chipsets, the speed was brought up to 133 MHz (PC133).

Another innovation in SDRAM is the small EEPROM chip called the Serial Presence Detect chip, which is mounted on the modules. It is a very small chip containing data on the modules speed, etc.

Notes on the physical RAM

RAM stands for Random Access Memory. Physically, RAM consists of small electronic chips which are mounted in modules (small printed circuit boards). The modules are installed in the PC’s motherboard using sockets — there are typically 2, 3 or 4 of these. On this motherboard there are only two, and that’s a bit on the low side of what is reasonable.

Figure 128. RAM modules are installed in sockets on the motherboard. In the background you see the huge fan on a Pentium 4 processor.

Data exchange - the motherboard

The ROM chips contain instructions, which are specific for that particular motherboard. Those programs and instructions will remain in the PC throughout its life; usually they are not altered.

Primarily the ROM code holds start-up instructions. In fact there are several different programs inside the start-up instructions, but for most users, they are all woven together. You can differentiate between:

1. POST (Power On Self Test)
2. The Setup instructions, which connect with the CMOS instructions
3. BIOS instructions, which connect with the various hardware peripherals
4. The Boot instructions, which call the operating system (DOS, OS/2, or Windows )

All these instructions are in ROM chips, and they are activated one by one during start-up. Let us look at each part.

The von Neumann Model of the PC

Computers have their roots 300 years back in history. Mathematicians and philosophers like Pascal, Leibnitz, Babbage and Boole made the foundation with their theoretical works. Only in the second half of this century was electronic science sufficiently developed to make practical use of their theories.

The modern PC has roots that go back to the USA in the 1940s. Among the many scientists, I like to remember John von Neumann (1903-57). He was a mathematician, born in Hungary. We can still use his computer design today. He broke computer hardware down in five primary parts:

1. CPU
2. Input
3. Output
4. Working memory
5. Permanent memory

Actually, von Neumann was the first to design a computer with a working memory (what we today call RAM). If we apply his model to current PCs, it will look like this:

The PC's success

The PC came out in 1981. In less than 20 years, it has totally changed our means of communicating. When the PC was introduced by IBM, it was just one of many different micro data processors. However, the PC caught on. In 5-7 years, it conquered the market. From being an IBM compatible PC, it became the standard.

If we look at early PCs, they are characterized by a number of features. Those were instrumental in creating the PC success.

1. The PC was from the start standardized and had an open architecture.
2. It was well documented and had great possibilities for expansion.
3. It was inexpensive, simple and robust (definitely not advanced).

The PC started as IBM's baby. It was their design, built over an Intel processor (8088) and fitted to Microsoft's simple operating system MS-DOS.

Since the design was well documented, other companies entered the market. They could produce functionable copies (clones) of the central system software (BIOS). The central ISA bus was not patented. Slowly, a myriad of companies developed, manufacturing IBM compatible PCs and components for them.

The Clone was born. A clone is a copy of a machine. A machine, which can do precisely the same as the original (read Big Blue - IBM). Some of the components (for example the hard disk) may be identical to the original. However, the Clone has another name (Compaq, Olivetti, etc.), or it has no name at all. This is the case with "the real clones." Today, we differentiate between:

1. Brand names, PCs from IBM, Compaq, AST, etc. Companies which are so big, so they develop their own hardware components.

2. Clones, which are built from standard components. Anyone can make a clone.

Since the basic technology is shared by all PCs, I will start with a review of that.

Introduction to the PC

The technical term for a PC is micro data processor . That name is no longer in common use. However, it places the PC in the bottom of the computer hierarchy:

1. Supercomputers and Mainframes are the largest computers - million dollar machines, which can occupy more than one room. An example is IBM model 390.

2. Minicomputers are large powerful machines. They typically serve a network of simple terminals. IBM's AS/400 is an example of a minicomputer.

3. Workstations are powerful user machines. They have the power to handle complex engineering applications. They use the UNIX or sometimes the NT operating system. Workstations can be equipped with powerful RISC processors like Digital Alpha or MIPS.

4. The PCs are the Benjamins in this order: Small inexpensive, mass produced computers. They work on DOS, Windows , or similar operating systems. They are used for standard applications.

The point of this history is, that Benjamin has grown. He has actually been promoted to captain! Todays PCs are just as powerful as minicomputers and mainframes were not too many years ago. A powerful PC can easily keep up with the expensive workstations. How have we advanced this far?