The average person who uses a computer on a regular basis doesn’t think about what happens inside a computer once the power is turned on. As long as their version of MS Windows pops up within a few seconds, most people are quite content to continue on with what they want to do on their computer. A computer goes through many processes from the moment the power is turned on before its operating system (ex. Windows, Linux) is fully loaded and takes over.

The operating system is stored on the hard disk of a computer. It is stored on the hard disk because this type of storage is much less expensive and an operating system requires a large amount of storage space. So, in order to make computers more economical, they are designed to use a combination of ROM, DRAM, and hard disks. An explanation of each follows.

Once the power switch is turned on, the “boot-up” process begins. To “boot-up” a computer simply means to start it. Electricity then flows through all of the chips and their circuits. The instructions for what the computer is supposed to do next are found in the Read Only Memory, Basic Input/Output System (ROM BIOS). ROM is memory that can only be read from and has information that is permanently burned into it. It is nonvolatile and will not be lost or disappear once the power is turned off.

ROM BIOS or just BIOS, is designed to begin giving commands as soon as it receives power. The BIOS contains an entire set of instructions, in effect a computer program written into the chip that manages the boot-up process. Without the BIOS, the computer would not know what to do next. The first task that BIOS completes is to make sure that all of the hardware components are working properly (for example: disk drives, external buses, the mouse, the printer). This is called a power-on self-test (POST). After the POST is complete, the BIOS activates other chips on different cards installed in the computer (SCSI and graphics cards) and provides a set of low-level routines that the operating system uses to interface to different hardware devices such as the keyboard, mouse, printer, etc.

Once the POST is complete, the BIOS hands the next stage in the boot-up process over to the central processing unit (CPU). The CPU is a one chip processor or microprocessor that has two distinct capabilities:

1. The CPU carries out all of the mathematical and logical operations including basic math and comparisons of two or more numbers.

2. The CPU has the ability to intelligently manage the flow of instructions and data going into and out of its circuits.

The last instruction that the ROM sends to the CPU is to go to a specific location or address to find its next instruction. An address is a string of numbers that gives directions to where something can be found, much like an address on an envelope. Computers use addresses to keep track of information much the same way as the post office uses them to find residences and businesses. The bigger the number in an address the more locations it can refer to. Most current computers use a 32-bit address space for memory, which means that there can be over four billion separate locations to hold information.

Sometimes the most important aspects of a subject are not immediately obvious. Keep reading to get the complete picture.

The instruction that the ROM BIOS wants the CPU to carry out is sent through a chip on a bus (a set of wires) to the address specified. The data bus is able to carry information into and out of the chip within the CPU. The information is not available within the CPU so it has to look elsewhere. The CPU then sends the address on another bus called an address bus. When the CPU does this, it is called a fetch. The address bus is “fetching” information from elsewhere within the computer. The address bus is only able to carry instructions out of the CPU.

The address bus fetches information from the computer’s memory. Memory is a type of silicon chip that can hold instructions or data. This type of memory can be read from or written to by the CPU, but this type of memory or Dynamic Random Access Memory (DRAM) is volatile. Once the power is turned off, the DRAM looses its memory or information. Since the DRAM is basically a blank slate, the CPU has within, a set of sequential instructions as to where to look for the required information.

Before the address bus can get to memory, it has to pass through a set of chips called a chipset. The chipset refers to a group of chips that provide an intelligent interface for the core components of a computer – CPU, memory, graphics, I/O system, described as core logic or glue logic. If the information that the chipset requires is not in memory, the chipset then sends or redirects it to the Input/Output (I/O) bus. The I/O bus connects the chipset to other places where the information is stored, such as the hard disk. The hard disk allows the CPU to read from it and to write to it. The hard disk is non-volatile so it retains its data or information once the power is turned off. A hard disk is much slower at retrieving data from than memory but memory is much more expensive.

Once the hard disk receives the address (via the I/O bus and chipset), it retrieves the information and sends it back through the chipset and then puts it on the address bus back into the CPU. The chipset functions as a bridge for the two buses; the I/O bus and the address bus.

The CPU uses a four step sequence: fetch, decode, execute, and store. Since the CPU does not retain its memory, it has to obtain its information or fetch the information from elsewhere within the computer. To help with the speed of the process of fetching, the CPU has a pre-fetch area to make the information available more quickly.

Once the information has been fetched, it has to be decoded. Part of the decoding process of the CPU is to decide which circuits are appropriate to use for executing the instructions. Once that decision has been made, the CPU begins to execute the instructions. The part of the CPU where the actual execution of instructions takes place is called the Arithmetic Logical Unit (ALU). The ALU includes groups of transistors, known as logic gates, which are organized to carry out basic mathematical and logical operations. Logic gates are grouped into electrical circuits that execute the CPU’s instructions such as “add” two numbers or “compare” two numbers.

The final step of the CPU is to store the information. This final step takes place after the ALU completes its calculations. The results of the calculations are stored on a chip that has an area called a register. Registers can be accessed more quickly than any other kind of memory but are only for temporary holding (storage) of information.

The CPU also has a clock within it to keep the timing of all of the flow of information and processes of the computer. This clock is vital to the synchronization of all of the processes of the computer. This CPU clock controls all of the operations on its chip. The processes of the CPU can also be interrupted by an external interrupt controller chip which is part of the chipset. The chipset contains a small database of interrupt vector (numerical table). When an interrupt signal comes onto the chip, the CPU saves what it is doing and goes to the interrupt vector to find the address of the instruction that the interrupt is telling it to execute instead. Once it is finished with the interrupt, it goes back to what it was doing. The CPU finds what it was doing in a register called a stack. If interrupts were not possible, the CPU would have to complete one task before it could start another causing the speed to be greatly reduced.

Now that the CPU has found the operating system, loaded it into memory, the operating system takes over and the computer is now ready to be used by its owner. The user can now check email, play a game, or do whatever they wanted to do when they started the computer.

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The average person who uses a computer on a regular basis doesn’t think about what happens inside a computer once the power is turned on. As long as their version of MS Windows pops up within a few seconds, most people are quite content to continue on with what they want to do on their computer. A computer goes through many processes from the moment the power is turned on before its operating system (ex. Windows, Linux) is fully loaded and takes over.

The operating system is stored on the hard disk of a computer. It is stored on the hard disk because this type of storage is much less expensive and an operating system requires a large amount of storage space. So, in order to make computers more economical, they are designed to use a combination of ROM, DRAM, and hard disks. An explanation of each follows.

Once the power switch is turned on, the “boot-up” process begins. To “boot-up” a computer simply means to start it. Electricity then flows through all of the chips and their circuits. The instructions for what the computer is supposed to do next are found in the Read Only Memory, Basic Input/Output System (ROM BIOS). ROM is memory that can only be read from and has information that is permanently burned into it. It is nonvolatile and will not be lost or disappear once the power is turned off.

ROM BIOS or just BIOS, is designed to begin giving commands as soon as it receives power. The BIOS contains an entire set of instructions, in effect a computer program written into the chip that manages the boot-up process. Without the BIOS, the computer would not know what to do next. The first task that BIOS completes is to make sure that all of the hardware components are working properly (for example: disk drives, external buses, the mouse, the printer). This is called a power-on self-test (POST). After the POST is complete, the BIOS activates other chips on different cards installed in the computer (SCSI and graphics cards) and provides a set of low-level routines that the operating system uses to interface to different hardware devices such as the keyboard, mouse, printer, etc.

Once the POST is complete, the BIOS hands the next stage in the boot-up process over to the central processing unit (CPU). The CPU is a one chip processor or microprocessor that has two distinct capabilities:

1. The CPU carries out all of the mathematical and logical operations including basic math and comparisons of two or more numbers.

2. The CPU has the ability to intelligently manage the flow of instructions and data going into and out of its circuits.

The last instruction that the ROM sends to the CPU is to go to a specific location or address to find its next instruction. An address is a string of numbers that gives directions to where something can be found, much like an address on an envelope. Computers use addresses to keep track of information much the same way as the post office uses them to find residences and businesses. The bigger the number in an address the more locations it can refer to. Most current computers use a 32-bit address space for memory, which means that there can be over four billion separate locations to hold information.

Sometimes the most important aspects of a subject are not immediately obvious. Keep reading to get the complete picture.

The instruction that the ROM BIOS wants the CPU to carry out is sent through a chip on a bus (a set of wires) to the address specified. The data bus is able to carry information into and out of the chip within the CPU. The information is not available within the CPU so it has to look elsewhere. The CPU then sends the address on another bus called an address bus. When the CPU does this, it is called a fetch. The address bus is “fetching” information from elsewhere within the computer. The address bus is only able to carry instructions out of the CPU.

The address bus fetches information from the computer’s memory. Memory is a type of silicon chip that can hold instructions or data. This type of memory can be read from or written to by the CPU, but this type of memory or Dynamic Random Access Memory (DRAM) is volatile. Once the power is turned off, the DRAM looses its memory or information. Since the DRAM is basically a blank slate, the CPU has within, a set of sequential instructions as to where to look for the required information.

Before the address bus can get to memory, it has to pass through a set of chips called a chipset. The chipset refers to a group of chips that provide an intelligent interface for the core components of a computer – CPU, memory, graphics, I/O system, described as core logic or glue logic. If the information that the chipset requires is not in memory, the chipset then sends or redirects it to the Input/Output (I/O) bus. The I/O bus connects the chipset to other places where the information is stored, such as the hard disk. The hard disk allows the CPU to read from it and to write to it. The hard disk is non-volatile so it retains its data or information once the power is turned off. A hard disk is much slower at retrieving data from than memory but memory is much more expensive.

Once the hard disk receives the address (via the I/O bus and chipset), it retrieves the information and sends it back through the chipset and then puts it on the address bus back into the CPU. The chipset functions as a bridge for the two buses; the I/O bus and the address bus.

The CPU uses a four step sequence: fetch, decode, execute, and store. Since the CPU does not retain its memory, it has to obtain its information or fetch the information from elsewhere within the computer. To help with the speed of the process of fetching, the CPU has a pre-fetch area to make the information available more quickly.

Once the information has been fetched, it has to be decoded. Part of the decoding process of the CPU is to decide which circuits are appropriate to use for executing the instructions. Once that decision has been made, the CPU begins to execute the instructions. The part of the CPU where the actual execution of instructions takes place is called the Arithmetic Logical Unit (ALU). The ALU includes groups of transistors, known as logic gates, which are organized to carry out basic mathematical and logical operations. Logic gates are grouped into electrical circuits that execute the CPU’s instructions such as “add” two numbers or “compare” two numbers.

The final step of the CPU is to store the information. This final step takes place after the ALU completes its calculations. The results of the calculations are stored on a chip that has an area called a register. Registers can be accessed more quickly than any other kind of memory but are only for temporary holding (storage) of information.

The CPU also has a clock within it to keep the timing of all of the flow of information and processes of the computer. This clock is vital to the synchronization of all of the processes of the computer. This CPU clock controls all of the operations on its chip. The processes of the CPU can also be interrupted by an external interrupt controller chip which is part of the chipset. The chipset contains a small database of interrupt vector (numerical table). When an interrupt signal comes onto the chip, the CPU saves what it is doing and goes to the interrupt vector to find the address of the instruction that the interrupt is telling it to execute instead. Once it is finished with the interrupt, it goes back to what it was doing. The CPU finds what it was doing in a register called a stack. If interrupts were not possible, the CPU would have to complete one task before it could start another causing the speed to be greatly reduced.

Now that the CPU has found the operating system, loaded it into memory, the operating system takes over and the computer is now ready to be used by its owner. The user can now check email, play a game, or do whatever they wanted to do when they started the computer.

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The term “expansion bus “is a frequent term in vintage computer terminology which requires elaboration. Much of the legacy of vintage bus systems are in our current computer systems today.

To begin with the “expansion bus” is a data highway for computer data information to travel on: the bandwidth is in essence the number of lanes. The bigger the bandwidth the more data can be sent. As examples, an 8 megabyte bandwidth means that data can be sent in 8 bits chunks. Our current systems use between 32 bit and now 64 bit bandwidth.

An expansion bus is where cards connect to the computer; Cards have an expansion edge, which fits snugly into the bus much like an electrical plug fits into a wall socket.

When cards are plugged into the bus, they communicate with the system, sometimes through the BIOS and others not. (The BIOS is the basic input /output system that tells the computer how to move data from the different components.) The 8, 16 or 32 bit bandwidth is an important consideration due to communication time between the cards. For example you have a 16 bit vintage 286 PC and it is sending out data at 16 bits a: your video card is also 8 bits. If you have an older 8 bit bus, such as in early IBM PCs and clones, the bus will become a bottleneck in the system; it is like having a 4 lane highway connected to another 4 lane highway by way of a 1 lane road. At most times regardless of the faster 4 lane highway traffic will be slow – limited by the single lane connection road.

There were basically 3 types of expansion bus available in vintage computers: ISA, MCA, EISA systems.

Each early development in major ways paved the way for the later systems which indeed we take for granted today. This was both in terms of hardware and basic concepts in our computer systems and technology as well as computer marketing that we take for granted today as simple basic facts of life without any consideration due.

Basically the newer buses offered increased performance over the older technology buses.

The basic explanations of the buses are as follows:

The 3 bus standards to note were Industry Standard Architecture (ISA) .Micro Channel Channel Architecture (MSA) and Extended Industry Standard (EISA) bus systems.

Industry Standard Architecture (ISA). This was the original AT bus also called an ISA bus. It was the original 8 bit IBM PC bus which was bumped up to 16 bits at some point in its later development. Fine for a 16 bit 286 or very early 386 computers

Micro Channel Architecture (MSA). This was an early 32 bit bus system which was not received well but set the stage for an industry consortium of the major non IBM computer manufacturers ( at the time referred to as “The Group of Nine) to develop the EISA standard bus.

Extended Industry Standard Architecture (EISA). The EISA bus standard was a standard of its own right which was 32 bit, included bus mastering and importantly remained compatible with previous older expansion cards. 32 bit systems were first to incorporate in later 386 systems. The 486 line solidified and standardized the 32 bit systems in the established software of the day.

Backward compatibility at the time was a novel new concept which has remained an important consideration in the computer industry.

EISA slots would accommodate both the ISA and EISA expansion slots to allow hardware upgrades, However the EISA expansion boards would be of little advantage and would seldom work in the older ISA expansion slots.

On the other hand the Micro Channel setup was not backward compatible. On the one hand the Micro Channel developers were free to initiate new radical changes in computer development and hardware which would have allowed for major new useful features in computer software. However owners of previous systems would have been left with then obsolete vintage useless hardware which would have been of no use and certainly little financial value.

Hence there was a lot of resistance to the Micro Channel bus setup.

It died a lingering death with its legacy living on in the aspirations of features offered in future developments and standards.

Thus the die was set for future hardware standards and software function as well as standard computer marketing concepts that we take for granted like mother’s milk today.

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