Overview of basics

Overview of basics

Book chapter 2 Computer Organization and Architecture By William Stallings Pub.: Prentice-Hall International, Inc. The evolution of computers has been characterized by increasing processor speed, decreasing component size, increasing memory size, and

increasing I/O capacity and speed. Anything more??? HW. One factor responsible for the great increase in processor speed is the shrinking size of microprocessor components;

this reduces the distance between components and hence increases speed. However, the true gains in speed in recent years have come from the organization of the processor, including heavy use of pipelining and parallel execution techniques and

the use of speculative execution techniques (tentative execution of future instructions that might be needed). All of these techniques are designed to keep the processor busy as much of the time as possible. A critical issue in computer system design is Balancing the performance of the various elements so that gains in performance in one area are not handicapped by a lag in other areas. In particular, processor speed has increased more rapidly than memory access

time. A variety of techniques is used to compensate for this mismatch, including caches, wider data paths from memory to processor, and more intelligent memory chips. Factors Affecting Processor Speed There are many factors which affect how fast your computer can process data and instructions:

The amount of RAM memory The speed and generation of your CPU (the system clock) The size of the Register on your CPU The Bus type and speed The amount of Cache memory Read & HW: http:// www.alf.sd83.bc.ca/courses/it12/using_it/processor_speed.htm How Registers Affect Speed A register is a high-speed memory area on the CPU, which hold data and instructions currently being processed.

Most CPUs sold today, for both PCs and Macintosh computers, have 64-bit registers. The size of the registers, which is sometimes called the word size, indicates the amount of data with which the computer can work at any given time. The bigger the word size, the more quickly the computer can process a set of data. Occasionally, you will hear people refer to "32-bit processors," or "64-bit processors," or

even "64-bit computers." This terminology refers to the size of the registers in the processor. If all other factors are kept equal, a CPU with 32-bit registers can process data twice as fast as one with 16-bit registers. Memory and Computing Power

The amount of RAM in a computer can have a profound effect on the computer's power. More RAM means the computer can use bigger, more powerful programs, and those programs can access bigger data files. More RAM also can make the computer run faster. The computer does not necessarily have to load an entire program into memory to run it. However, the greater the amount of the program that fits into memory, the faster the program runs.

For example, a PC with 16 MB of RAM is able to run Microsoft Windows 98, even though the program actually occupies about 195 MB of disk storage space. When you run Windows, the program does not need to load all its files into memory to run properly. It loads only the most essential parts into memory.

When the computer needs access to other parts of the program on the disk, it can unload, or swap out, nonessential parts from RAM to the hard disk. Then the computer can load, or swap in, the program code or data it needs. This process is called swapping. While this is an effective method for managing a

limited amount of memory, it can result in slow system performance because the CPU, memory, and disk are continuously occupied with the swapping process. If your PC has 64 MB of RAM (or more), you will notice a dramatic difference in how fast Microsoft Windows 98 runs because the CPU will need to swap program instructions between RAM and the hard disk Computer's Internal Clock

Every microcomputer has a system clock, but the clock's primary purpose is not to keep the time of day. The clock is driven by a quartz crystal. When electricity is applied, the molecules in the crystal vibrate millions of times per second, a rate that never changes. The speed of the vibrations is determined by the thickness of the crystal. The computer uses the vibrations of the quartz in the

system clock to time its processing operations. Over the years, system clocks have become steadily faster. E.g., the first PC operated at 4.77 megahertz. Hertz (Hz) is a measure of cycles per second. Megahertz (MHz) means "millions of cycles per second."

The computer's operating speed is tied to the speed of the system clock. For example, if a computer's clock speed is 300 MHz, it "ticks" 300 million times per second. A clock cycle is a single tick, or the time it takes to turn a transistor off and back on again. A processor can execute an instruction in a given number of clock cycles. As the system's clock speed increases, so does the number of instructions it can carry out each second. Clock speed has a tremendous impact on CPU performance. A CPU operating at 300 MHz can

process data nearly twice as fast as the same one operating at 166 MHz. & increasing Bus In microcomputers, the term bus refers to the path between the components of a computer. There are two main buses in a computer:

the internal (or system) bus the external (or expansion) bus The system bus resides on the motherboard and connects the CPU to other devices that reside on the motherboard. An expansion bus connects external devices, such as the keyboard, mouse, modem, printer, etc., to the CPU. Cables from disk drives and some other internal devices may also be The

system bus has two parts: the data bus and the address bus The address bus leads from the CPU to RAM. The data bus connects the CPU to memory as well as all the storage, input/output, and communication devices. ..Bus: System Bus Data Bus The data bus is an electrical path that

connects the CPU, memory, and the other hardware devices on the motherboard. Actually, the bus is a group of parallel wires. The number of wires in the bus affects the speed at which data can travel between hardware components, just as the number of lanes on a highway affects how long it takes people to reach their destinations.

Because each wire can transfer 1 bit of data at a time, an 8-wire bus can move 8 bits at a time, which is a full byte. A 16-bit bus can transfer 2B, and a 32bit bus can transfer 4B at a time. Newer model computers have a 64-bit data bus, which transfers 8 bytes at a time. With a wider bus, the computer can move more data in the same amount of time (or the same amount of data in less time). ..Bus: System Bus Address Bus The

address bus is a set of wires similar to the data bus. The address bus connects only the CPU and RAM and carries only memory addresses. Remember, each byte in RAM is associated with a number, which is its memory address. Q. In theory, today's CPUs have address buses that are wide enough to address 64 GB of RAM. Requests for data are sent from the CPU to RAM along the address bus. The request consists of a memory address. The data comes back to the CPU via the data

bus. ..Bus Types PC buses are designed to match the capabilities of the devices attached to them. When CPUs could send and receive only 1 byte of data at a time, there was no point in connecting them to a bus that could move more data. As microprocessor technology improved, however, chips were built that could send and receive more data at once,

and improved bus designs created wider paths through which the data could flow. Common bus technologies include: Industry Standard Architecture (ISA) bus Local bus Peripheral Component Interconnect (PCI) bus Accelerated Graphics Port (AGP) bus

Universal Serial Bus (USB) IEEE 1394 The Industry Standard Architecture (ISA) bus is a 16-bit data bus. ISA was the industry standard on its release in the mid-1980s and is still used in many computers to attach slower devices (such as modems and input devices) to the CPU. ISA is a type of bus that carries information between an ISA style expansion slot and the

CPU. One 8-bit and five 16-bit ISA slots on a motherboard Variants

Wiki PC/104 - Embedded variant of ISA Low Pin Count (LPC) - Low pin count version of ISA Extended Industry Standard Architecture (EISA) Micro Channel architecture (MCA) Local bus technology was developed to attach faster devices to the CPU.

A local bus is an internal system bus that runs between components on the motherboard. Most system buses use some type of local bus technology today and are coupled with one or more kinds of expansion bus. Peripheral Component Interconnect (PCI) bus is a type of local bus designed by Intel to make it easier to integrate new data types, such as audio, video, and graphics.

Most new computers use a PCI bus and PCI expansion slots. A PCI bus connects PCI expansions cards to the CPU. Since June 1992. Visit: http://pcisig.com/ - the community responsible for developing and maintaining the standardized approach to peripheral component I/O data transfers. 133 MB/s (32-bit at 33 MHz the standard configuration)

266 MB/s (32-bit at 66 MHz or 64-bit at 33 MHz) 533 MB/s (64-bit at 66 MHz) Three 5-volt 32-bit PCI expansion slots on a motherboard (PC bracket on left side) Accelerated Graphics Port (AGP) bus incorporates a special architecture that allows video cards to access the system's RAM directly, greatly increasing the speed of graphics performance.

The AGP standard has led to the development of many types of accelerated video cards that support 3-D and full-motion video. While AGP improves graphics performance, it cannot be used with all PCs. The system must use a chip set that supports the AGP standard. Most new computers feature AGP graphics capabilities in addition to a PCI system bus and an expansion bus. Universal AGP slot (brown, top) and PCI 2.2 slot (white beige, bottom)

Q. What is the difference between AGP and PCI? The biggest difference between AGP and PCI graphics cards is that AGP cards can access the system memory to help with complex operations such as texture mapping. PCI cards can only access the memory available on the actual card. AGP doesn't share bandwidth with other devices, whereas PCI cards do. HW: https://pc.net/helpcenter/answers/difference_between_agp_and_pci

Universal Serial Bus (USB) - not only provides fast data transfer speeds, it also eliminates the need for expansion slots and boards. Most new PCs and Macintosh computers feature at least one USB port, and each USB port can support 127 different devices. If you have USB-compliant devices such as key boards, mice, printers, and modems, you can plug them all into a single USB port.

Length: 25 m (6 ft 7 in16 ft 5 in) (by category) Width: 12 mm (type-A) | 8.45 mm (type-B) | 6.8 mm (mini/micro) | 8.25 mm (type-C) Height: 4.5 mm (type-A) | 7.26 mm (type-B) | 10.44 mm (type-B SuperSpeed) | 1.83 mm (mini/micro) | 2.4 mm (type-C) Different USB connectors: From left to right:

(1) (2) (3) (4) (5) (6) male Micro USB B-Type, proprietary UC-E6, male Mini USB (5-pin) B-type, female A-type, male A-type, male B-type.

Shown with a centimeter ruler. Female A-type connector (4th from left) is "upside down" to show the pins. See: https://en.wikipedia.org/wiki/USB HW & Read Micro USB Live USB

Wireless USB USB flash drive IEEE 1394 IEEE 1394 is an interface standard for a serial bus for high-speed communications and isochronous real-time data transfer. It was developed in the late 1980s and early 1990s by Apple, which called it FireWire. The 1394 interface is also known by the brand i.LINK (Sony), and Lynx (Texas

Instruments). 9-pin FireWire 800 connector Alternative Ethernet-style cabling used by 1394c Traditionally, the performance of computer buses was measured by the number of bits they could transfer at one time. Hence, the newest 64-bit buses are typically considered the fastest available. However, buses are now also being

measured according to their data transfer rates - the amount of data they can transfer in a second. This type of performance is usually measured in megabits per second (Mbps) or megabytes per second (MBps). For example,

A USB bus has a data transfer rate of 12 Mbps. An IEEE 1394 bus has a data transfer rate of 400 Mbps. AGP buses are typically rated at 266 MBps but can support data transfer rates of more than 1 GBps. PCI buses offer data transfer rates of 133 MBps. Some manufacturers also rate the speed of their system buses in megahertz.

For years, system buses ran at a speed of 66 MHz; contemporary systems offer bus speeds of 100 MHz and 200 MHz. When coupled with a fast processor, a high-speed bus can result in an exceptionally highperformance system. Cache Memory Moving data between RAM and the CPU's registers is one of the most timeconsuming operations a CPU must perform, simply because RAM is much slower than the CPU. A partial solution to this problem is to

include cache memory. Cache (pronounced cash) memory is extremely fast memory, which hold the most recently used data and instructions. Why so fast? When a program is running and the CPU needs to read data or program instructions from RAM, the CPU checks first to see whether the data is in cache memory. If the data is not there, the CPU reads the

data from RAM into its registers, but it also loads a copy of the data into cache memory. The next time the CPU needs that same data, it finds it in the cache memory and saves the time needed to load the data from RAM. There are 2 types of cache memory,

L1 and L2 The difference being their speed and size. L1, or level 1 cache is much faster, but also holds a lot less data than L2, or level 2 cache. Since the late 1980s, L1 cache memory has been built into the CPU. The first CPU caches came with 0.5 KB, then 8 KB, then 16 KB 32 KB 256 KB 512 KB

L1 cache built in. L2 cache can either be "on die", meaning it is built into the CPU, or it can be built into the motherboard. The closer cache memory is to the CPU, the faster it is. Therefore, a CPU with both L1 and L2 cache on die will be faster than a CPU with its L2 cache on the motherboard. Many PCs sold today have 512 KB, 1024 KB, or 2 Mb of L2 cache memory.

The cache speeds up processing by storing frequently used data or instructions in its high-speed memory. External (Level-2) cache is shown here, but most computers also have internal (Level-1) cache memory circuitry built into the CPU. Read: http://www.hardwaresecrets.com/how-the-cache-memo ry-works/3 /

HW: PPT 10min https:// es.cs.uni-kl.de/publications/data/Jede15.pdf Eric Jedermann, Exposed Datapath Processor Architecture Implementation Survey Harvard vs. Princeton / Von Neumann architecture? Institute for Advanced Study (IAS) The

IAS machine was the first electronic computer to be built at the Institute for Advanced Study (IAS) in Princeton, New Jersey, U.S. It is sometimes called the von Neumann machine, since the paper describing its design was edited by John von Neumann, a mathematics professor at both Princeton University and IAS. wiki Q. Mention 5 things you need to

consider for this simple architecture. What was in the mind of Von Neumann & Co. while designing this? 1. CA Because the device is primarily a computer, it will have to perform the elementary operations of arithmetic most frequently. + - x / It is therefore reasonable that it should contain specialized organs for just these operations. It must be observed, however, that while this

principle as such is probably sound, the specific way in which it is realized requires close scrutiny. At any rate a central arithmetical part of the device will probably have to exist and this constitutes the first specific part: CA. 2. CC The logical control of the device, that is, the proper sequencing of its operations, can be most efficiently carried out by a central control organ. 3. M

Any device which is to carry out long and complicated sequences of operations (specifically of calculations) must have a considerable memory . . . The instructions which govern a complicated problem may constitute considerable material, particularly so, if the code is circumstantial (which it is in most arrangements). This material must be remembered. At any rate, the total memory constitutes the third specific part of the device: M. The three specific parts CA, CC, and M

correspond to the associative neurons in the human nervous system. It remains to discuss the equivalents of the sensory or afferent and the motor or efferent neurons. These are the input and output organs of the device. The device must be endowed with the ability to maintain input and output (sensory and motor) contact with some specific medium of this type. The medium will be called the outside recording medium of the device: R 4. I

The device must have organs to transfer . . . information from R into its specific parts C and M. These organs form its input: I. It will be seen that it is best to make all transfers from R (by I) into M and never directly from C. 5. O The device must have organs to transfer . . . from its specific parts C and M into R. These organs form its output: O. It will be seen that it is again best to make all

transfers from M (by O) into R, and never directly from C. Lets think about its memory formats 1000 Word storage locations! 40 bits each = 1 Do you need storage locations within? Registers!

Reg Memory buffer register (MBR): Contains a word to be stored in memory or sent to the I/ O unit, or is used to receive a word from memory or from the I/O unit. Memory address register (MAR): Specifies the address in memory of the word to be written from or read into the MBR. Instruction register (IR): Contains the 8-bit opcode instruction being executed.

Reg Instruction buffer register (IBR): Employed to hold temporarily the right-hand instruction from a word in memory. Program counter (PC): Contains the address of the next instruction-pair to be fetched from memory. Accumulator (AC) and multiplier quotient (MQ): Employed to hold temporarily operands and results of ALU operations. E.g., the result of multiplying two 40-bit numbers is an 80-bit

number; the most significant 40 bits are stored in the AC and the least significant in

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