Some people confuse BIOS with the CMOS RAM in a system. This confusion is aided by the fact that the Setup program in the BIOS is used to set and store the configuration settings in the CMOS RAM. They are, in fact, two totally separate components.
The BIOS on the motherboard is stored in a fixed ROM chip. Also on the motherboard is a chip called the RTC/NVRAM chip, which stands for real-time clock/nonvolatile memory. This is where the BIOS Setup information is stored, and it is actually a digital clock chip with a few extra bytes of memory thrown in. It is usually called the CMOS chip because it is made using CMOS (complimentary metal-oxide semiconductor) technology. 
The first example of this ever used in a PC was the Motorola MC146818 chip, which had 64 bytes of storage, of which 10 bytes were dedicated to the clock function. Although it is called nonvolatile, it is actually volatile, meaning that without power, the time/date settings and the data in the RAM portion will in fact be erased. It is called nonvolatile because it is designed using CMOS technology, which results in a chip that runs on very little power. A battery in the system, rather than the AC wall current, provides that power. This is also why most people call this chip the CMOS RAM chip; although not technically accurate (almost all modern chips use a form of CMOS technology), that is easier to say than the RTC/NVRAM chip. Most RTC/NVRAM chips run on as little as 1 microamp (millionth of an amp), so they use very little battery power to run. Most lithium coin cell batteries can last up to 5 years or more before the battery runs out and the information stored (as well as the date and time) is lost. Some systems use special versions of these chips made by Dallas Semiconductor, Benchmarq, or Odin (such as the DS12885 and DS12887) that include both the RTC/NVRAM chip and the battery in a single component. 
When you enter your BIOS Setup, configure your hard disk parameters or other BIOS Setup settings, and save them, these settings are written to the storage area in the RTC/NVRAM (otherwise called CMOS RAM) chip. Every time your system boots up, it reads the parameters stored in the CMOS RAM chip to determine how the system should be configured. A relationship exists between the BIOS and CMOS RAM, but they are two distinctly different parts of the system
It is often difficult for people to understand the difference between hardware and software in a PC system. The differences can be difficult because they are both very much intertwined in the system design, construction, and operation. Understanding these differences is essential to understanding the role of the BIOS in the system.
BIOS is a term that stands for basic input/output system , which at the most basic level consists of low-level software that controls the system hardware. BIOS is essentially the link between hardware and software in a system. Most people know the term BIOS by another name— device drivers, or just drivers . BIOS is a single term that describes all the drivers (low-level hardware control programs) in a system working together to act as an interface between the hardware and the operating system software.What can be confusing is that some of the BIOS code is burned or flashed into a ROM chip that is both nonvolatile (it doesn’t get erased when the power is turned off) and read-only. This is a core part of the BIOS, but not all of it. The BIOS also includes ROM chips installed on adapter cards, as well as all the additional drivers loaded when your system boots up. The combination of the motherboard BIOS, adapter card BIOS, and device drivers loaded from disk contribute to the BIOS as a whole. The portion of the BIOS contained in ROM chips both on the motherboard and in some adapter cards is sometimes called firmware , which is a name given to software stored in chips rather than on disk. This causes some people to incorrectly think of the BIOS as a hardware component. A PC system can be described as a series of layers—some hardware and some software—that interface with each other. In the most basic sense, you can break a PC down into four primary layers, each of which can be broken down further into subsets The purpose of the layered design is to enable a given operating system and applications to run on different hardware. different machines with different hardware can each use different drivers (BIOS) to interface the unique hardware to a common operating system and applications. Thus, two machines with different processors, storage media, video display units, and so on can run the same application software. In this layered architecture, the application software programs talk to the operating system via what is called an Application Program Interface (API). The API varies according to the operating system you are using and consists of the various commands and functions the operating system can perform for an application. For example, an application can call on the operating system to load or save a file. This prevents the application itself from having to know how to read the disk, send data to a printer,or perform any other of the many functions the operating system can provide. Because the application is completely insulated from the hardware, you can essentially run the same applications on different machines; the application is designed to talk to the operating system rather than the hardware. 
The operating system then interfaces with or talks to the BIOS or driver layer. The BIOS consists of all the individual driver programs that operate between the operating system and the actual hardware. Assuch, the operating system never talks to the hardware directly; instead, it must always go through the appropriate drivers. This provides a consistent way to talk to the hardware. It is usually the responsibility of the hardware manufacturer to provide drivers for its hardware. Because the drivers must act between both the hardware and the operating system, the drivers typically are operating system specific. Thus, the hardware manufacturer must offer different drivers so that its hardware works under DOS, Windows 9x, Windows NT, Windows 2000, OS/2, Linux, and so on. Because many operating systems use the same internal interfaces, some drivers can work under multiple operating systems. For example, a driver that works under Windows Me often also works under Windows 98 and 95, and a driver that works under Windows XP also often works under Windows 2000 and NT. 
This is because Windows 95, 98, and Me are essentially variations on the same OS, as are Windows NT, 2000,and XP.Because the BIOS layer looks the same to the operating system no matter what hardware is above it(or underneath, depending on your point of view), the same operating system can run on a variety of systems. For example, you can run Windows XP on two systems with different processors, hard disks, video adapters, and so on, yet Windows XP will look and feel pretty much the same on both of them.This is because the drivers provide the same basic functions no matter which specific hardware is used. 
AMD took a gamble with its Athlon and Duron processors. With these processors, AMD decided for the first time to create a chip that was Intel compatible with regards to software but not directly hardware or pin compatible. Whereas the K6 series would plug into the same Socket 7 that Intel designed for the Pentium processor line, the AMD Athlon and Duron would not be pin compatible with the Pentium II/III and Celeron chips. This also meant that AMD could not take advantage of the previously existing chipsets and motherboards when the Athlon and Duron were introduced; instead, AMD would have to either create its own chipsets and motherboards or find other companies who would.
The gamble seems to have paid off. AMD bootstrapped the market by introducing its own chipset, referred to as the AMD-750 chipset (codenamed Irongate). The AMD 750 chipset consists of the 751 System Controller (North Bridge) and the 756 Peripheral Bus Controller (South Bridge). 
More recently, AMD introduced the AMD-760 chipset for the Athlon/Duron processors, which is the first major chipset on the market supporting DDR SDRAM for memory. It consists of two chips—the AMD-761 System Bus Controller (North Bridge) and the AMD-766 Peripheral Bus Controller (South Bridge). Other companies, such as VIA Technologies, NVIDIA, and SiS, have also introduced chipsets specifically designed for the Socket/Slot A processors from AMD. This has enabled the motherboard companies to make a variety of boards supporting these chips and the Athlon and Duron processors to takea fair amount of market share away from Intel in the process.
You can’t talk about chipsets today without discussing Intel because it currently owns the vast majority of the chipset market. It is interesting to note that we probably have Compaq to thank for forcing Intel into the chipset business in the first place!
The thing that really started it all was the introduction of the EISA bus designed by Compaq in 1989.At that time, it had shared the bus with other manufacturers in an attempt to make it a market standard. However, Compaq refused to share its EISA bus chipset—a set of custom chips necessary to implement this bus on a motherboard. Enter Intel, who decided to fill the chipset void for the rest of the PC manufacturers wanting to build EISA bus motherboards. As is well known today, the EISA bus failed to become a market success except for a short-term niche server business, but Intel now had a taste of the chipset business and this it apparently wouldn’t forget. With the introduction of the 286 and 386 processors, Intel became impatient with how long it took the other chipset companies to create chipsets around its new processor designs; this delayed the introduction of motherboards that supported the new processors.
For example, it took more than two years after the 286 processor was introduced for the first 286 motherboards to appear and just over a year for the first 386 motherboards to appear after the 386 had been introduced. Intel couldn’t sell its processors in volume until other manufacturers made motherboards that would support them, so it thought that by developing motherboard chipsets for a new processor in parallel with the new processor, it could jumpstart the motherboard business by providing ready-made chipsets for the motherboard manufacturers to use.Intel tested this by introducing the 420 series chipsets along with its 486 processor in April 1989. This enabled the motherboard companies to get busy right away, and in only a few months the first 486 motherboards appeared. Of course, the other chipset manufacturers weren’t happy; now they had Intel as a competitor, and Intel would always have chipsets for new processors on the market first!
Intel then realized that it made both processors and chipsets, which were 90% of the components on a typical motherboard. What better way to ensure that motherboards were available for its Pentium processor when it was introduced than by making its own motherboards as well and having these boards ready on the new processor’s introduction date. When the first Pentium processor debuted in 1993, Intel also debuted the 430LX chipset as well as a fully finished motherboard. Now, besides the chipset companies being upset, the motherboard companies weren’t too happy, either. Intel was not only the major supplier of parts needed to build finished boards (processors and chipsets), but was now building and selling the finished boards as well. By 1994, Intel dominated the processor and chipset markets and had cornered the motherboard market as well.
Now as Intel develops new processors, it develops chipsets and motherboards simultaneously, which means they can be announced and shipped in unison. This eliminates the delay between introducing new processors and waiting for motherboards and systems capable of using them, which was com mon in the industry’s early days. For the consumer, this means no waiting for new systems. Since the original Pentium processor in 1993, we have been able to purchase ready-made systems on the same day a new processor is released. In my seminars, I ask how many people in the class have Intel brand PCs. Of course, Intel does not sell or market a PC under its own name, so nobody thinks they have an “Intel-brand” PC. But, if your motherboard was made by Intel, for all intents and purposes you sure seem to have an Intel-brand PC, at least as far as the components are concerned. Does it really matter whether Dell, Gateway, or Micron put that same Intel motherboard into a slightly different looking case with their name on it? If you look under the covers, you’ll find that many, if not most, of the systems from the major manufacturers are really the same because they basically use the same parts. Although more and more major manufacturers are offering AMD Athlon- and Duron-based systems as alternatives to Intel’s, no manufacturer dominates AMD motherboard sales the way Intel has dominated OEM sales to major system manufacturers. To hold down pricing, many low-cost retail systems based on micro-ATX motherboards use non-Intel motherboards. But, even though many companies make Intel-compatible motherboards for aftermarket upgrades or local computer assemblers, Intel still dominates the major vendor OEM market for midrange and high-end systems.
Chipsets
We can’t talk about modern motherboards without discussing chipsets. The chipset is the motherboard; therefore, any two boards with the same chipsets are functionally identical. The chipset contains the processor bus interface (called front-side bus, or FSB), memory controllers, bus controllers,I/O controllers, and more. All the circuits of the motherboard are contained within the chipset. If the processor in your PC is like the engine in your car, the chipset represents the chassis. It is the framework in which the engine rests and is its connection to the outside world. The chipset is the frame,suspension, steering, wheels and tires, transmission, driveshaft, differential, and brakes. The chassis in your car is what gets the power to the ground, allowing the vehicle to start, stop, and corner. In the PC, the chipset represents the connection between the processor and everything else. The processor can’t talk to the memory, adapter boards, devices, and so on without going through the chipset. The chipset is the main hub and central nervous system of the PC. If you think of the processor as the brain, the chipset is the spine and central nervous system.
Because the chipset controls the interface or connections between the processor and everything else,the chipset ends up dictating which type of processor you have; how fast it will run; how fast thebuses will run; the speed, type, and amount of memory you can use; and more. In fact, the chipset might be the single most important component in your system, possibly even more important than the processor. I’ve seen systems with faster processors be outperformed by systems with slower procesor but a better chipset, much like how a car with less power might win a race through better cornering and braking. When deciding on a system, I start by choosing the chipset first because the chipset decision then dictates the processor, memory, I/O, and expansion capabilities.
Chipset Evolution
When IBM created the first PC motherboards, it used several discrete (separate) chips to complete the design. Besides the processor and optional math coprocessor, many other components were required to complete the system. These other components included items such as the clock generator, bus controller, system timer, interrupt and DMA controllers, CMOS RAM and clock, and keyboard controller.
Additionally, many other simple logic chips were used to complete the entire motherboard circuit, plus, of course, things such as the actual processor, math coprocessor (floating-point unit), memory,
Processor Upgrades
Since the 486, processor upgrades have been relatively easy for most systems. With the 486 and later processors, Intel designed in the capability to upgrade by designing standard sockets that would take a variety of processors. Thus, if you have a motherboard with Socket 3, you can put virtually any 486 processor in it; if you have a Socket 7 motherboard, it should be capable of accepting virtually any Pentium processor (or Socket 7-based third-party processor). To maximize your motherboard, you can almost always upgrade to the fastest processor your particular board will support. Because of the varieties of processor sockets and slots—not to mention voltages, speeds, and other potential areas of incompatibility—you should consult with your motherboard manufacturer to see whether a higher-speed processor will work in your board. Usually, that can be determined by the type of socket or slot on the motherboard, but other things such as the voltage regulator and BIOS can be deciding factors as well.
For example, if your motherboard uses Socket 370, you might be able to upgrade to the fastest 1.4GHz version of the Pentium III. Before purchasing a new CPU, you should verify that the motherboard has proper bus speed, voltage settings, and ROM BIOS support for the new chip. Rather than purchasing processors and adapters separately, I usually recommend you purchase them together in a module from companies such as Kingston or Evergreen 
Upgrading the processor can, in some cases, double the performance of a system. However, if you already have the fastest processor that will fit a particular socket, you need to consider other alternatives. In that case, you really should look into a complete motherboard change, which would let you upgrade to a Pentium 4 or Athlon XP processor at the same time. If your chassis design is not propri-etary and your system uses an industry-standard ATX motherboard design, I normally recommend changing the motherboard and processor rather than trying to find an upgrade processor that will work with your existing board.
Processor Specifications
Many confusing specifications often are quoted in discussions of processors. The following sections discuss some of these specifications, including the data bus, address bus, and speed. The next section includes a table that lists the specifications of virtually all PC processors. Processors can be identified by two main parameters: how wide they are and how fast they are. The speed of a processor is a fairly simple concept. Speed is counted in megahertz (MHz) and gigahertz (GHz), which means millions and billions, respectively, of cycles per second—and faster is better! The width of a processor is a little more complicated to discuss because three main specifications in a processor are expressed in width. They are ¦ Data I/O bus ¦ Internal registers ¦ Address bus 
First, I’ll present some tables describing the differences in specifications between all the PC processors; then the following sections will explain the width and other specifications in more detail. will become clearer that the Pentium Pro processor includes 256KB, 512KB, or 1MB of full-core speed L2 cache in a separate die within the chip. The earlier Pentium II/III processors include 512KB of half-core speed L2 cache on the processor card. The Celeron, Pentium II PE, and Pentium IIIE and IIIB processors include full-core speed L2 cache integrated directly within the processor die. The Celeron III uses the same die as the Pentium IIIE, but half of the on-die cache is disabled,leaving 128KB functional. Older Celerons were based on the Pentium II and III, whereas the Celeron 4 is actually aPentium 4. The later Pentium 4A includes 512KB of on-die full-core speed L2 cache.The transistor count figures do not include the external (of f-die) 256KB, 512KB, 1MB, or 2MB L2 cache built into the Pentium Pro, Pentium II/III, Xeon, and AMD Athlon CPU packages or the 2MB or 4MB of L3 cache in the Itanium. The external L2 cache in those processors contains an additional 15.5 (256KB), 31 (512KB), 62 million (1MB), or 124 million (2MB) transistors in separate chips, whereas the external 2MB or 4MB of L3 cache in the Itanium includes up to 300 million transistors! 
The original AMD Athlon included 512KB of L2 cache via separate chips, running at either onehalf, two-fifths, or one-third the core speed, and later Athlon TB (Thunderbird) or XP models include 256KB of on-die L2 running at full-core speed.
The brain or engine of the PC is the processor (sometimes called microprocessor), or central processing unit (CPU). The CPU performs the system’s calculating and processing. The processor is often the most expensive single component in the system (although graphics card pricing now surpasses it in some cases); in higher-end systems it can cost up to four or more times more than the motherboard it plugs into. Intel is generally credited with creating the first microprocessor in 1971 with the introduction of a chip called the 4004. Today Intel still has control over the processor market, at least for PC systems. 
This means that all PC-compatible systems use either Intel processors or Intel-compatible processors from a handful of competitors (such as AMD or VIA/Cyrix).Intel’s dominance in the processor market hadn’t always been assured. Although Intel is generally credited with inventing the processor and introducing the first one on the market, by the late 1970s the two most popular processors for personal computers were not from Intel (although one was a clone of an Intel processor). Personal computers of that time primarily used the Z-80 by Zilog and the 6502 by MOS Technologies. The Z-80 was noted for being an improved and less expensive clone of the Intel 8080 processor, similar to the way companies today such as AMD, VIA/Cyrix, IDT, and Rise Technologies have cloned Intel’s Pentium processors. In the Z-80 case, though, the clone had become far more popular than the original. Some might argue that AMD has achieved that type of status over the past year, but even though they have made significant gains, Intel still controls the PC processor market. Back then I had a system containing both of those processors, consisting of a 1MHz (yes, that’s 1, as in one megahertz!) 6502-based Apple II system with a Microsoft Softcard (Z-80 card) plugged into one of the slots. The Softcard contained a 2MHz Z-80 processor. This enabled me to run software for both processors on the one system. The Z-80 was used in systems of the late 1970s and early 1980s that ran the CP/M operating system, whereas the 6502 was best known for its use in the early Apple I and II computers (before the Mac). The fate of both Intel and Microsoft was dramatically changed in 1981 when IBM introduced the IBM PC, which was based on a 4.77MHz Intel 8088 processor running the Microsoft Disk Operating System (MS-DOS) 1.0. Since that fateful decision was made to use an Intel processor in the first PC,subsequent PC-compatible systems have used a series of Intel or Intel-compatible processors, with each new one capable of running the software of the processor before it—from the 8088 to the current Pentium 4/III/Celeron and Athlon/Duron. The following sections cover the various types of processor chips that have been used in personal computers since the first PC was introduced almost two decades ago. These sections provide a great deal of technical detail about these chips and explain why one type of CPU chip can do more work than another in a given period of time. 
I normally ask the question, “What exactly is a PC?” when I begin one of my PC hardware seminars.Of course, most people immediately answer that PC stands for personal computer, which in fact it does. They might then continue by defining a personal computer as any small computer system purchased and used by an individual. Unfortunately, that definition is not nearly precise or accurate enough for our purposes.
I agree that a PC is a personal computer, but not all personal computers are PCs. For example, an Apple Macintosh system is clearly a personal computer, but nobody I know would call a Mac a PC, least of all Mac users! For the true definition of what a PC is, you must look deeper. Calling something a PC implies that it is something much more specific than just any personal computer. One thing it implies is a family relation to the original IBM PC from 1981. In fact, I’ll go so far as to say that IBM literally invented the type of computer we call a PC today; that is, IBM designed and created the very first one, and IBM originally defined and set all the standards that made the PC distinctive from other personal computers. Note that it is very clear in my mind—as well as in the historical record—that IBM did not invent the personal computer. (Most recognize the historical origins of the personal computer in the MITS Altair, introduced in 1975.) IBM did not invent the personal computer, but it did invent what today we call the PC. Some people might take this definition a step further and define a PC as any personal computer that is “IBM compatible.” In fact, many years back,
PCs were called either IBM compatibles or IBM clones, in essence paying homage to the origins of the PC at IBM. The reality today is that although IBM clearly designed and created the first PC in 1981 and controlled the development and evolution of the PC standard for several years thereafter, IBM is no longer in control of the PC standard; that is, it does not dictate what makes up a PC today.
IBM lost control of the PC standard in 1987 when it introduced its PS/2 line of systems. Up until then, other companies that were producing PCs literally copied IBM’s systems right down to the chips; connectors; and even the shapes (form factors) of the boards, cases, and power supplies. After 1987, IBM abandoned many of the standards it created in the first place. That’s why for many years now I have refrained from using the designation “IBM compatible” when referring to PCs. If a PC is no longer an IBM-compatible system, what is it? The real question seems to be, “Who is in control of the PC standard today?” That question is best broken down into two parts. First, who is in control of PC software? Second, who is in control of PC hardware?
Who Controls PC Software?
Most of the people in my seminars don’t even hesitate for a split second when I ask this question;they immediately respond, “Microsoft!” I don’t think there is any argument with that answer.Microsoft clearly controls the operating systems used on PCs, which have migrated from the originalMS-DOS to Windows 3.1/95/98/Me, Windows NT/2000, and now Windows XP.
Microsoft has effectively used its control of the PC operating system as leverage to also control other types of PC software, such as utilities and applications. For example, many utility programs originally offered by independent companies, such as disk caching, disk compression, file defragmentation, file structure repair, and even simple applications such as calculator and notepad programs, are now bundled in (included with) Windows. Microsoft has even bundled more comprehensive applications such as Web browsers, ensuring an automatic installed base for these applications—much to the dismay of companies who produce competing versions.
Microsoft has also leveraged its control of the operating system to integrate its own networking software and applications suites more seamlessly into the operating system than others. That’s why it now dominates most of the PC software universe, from operating systems to networking software to utilities, from word processors to database programs to spreadsheets.
