C H A P T E R 3 Hardware: Input, Processing, and Output Devices

Table of Contents

Hardware - Basically, anything inanimate that you can touch. The computer, the disks, etc.

The Computer Central Processor The central processing unit (CPU), The arithmetic/logic unit (ALU) and the control unit

Registers High speed semiconductor memory. Data must be moved into registers for processing by the central processor

How the parts of a computer fit together (diagram)

Speed of Processing

Execution of an Instruction - instruction phaseFirst, the computer has to get a single program instruction, e.g., get the number at location 3489; put the current result into location 8925

Execution of an Instruction - execution phaseNext, the computer has to do what the instruction says

Pipelining - to get faster speeds, some machines can do mutiple operations (or the same operation on multiple numbers) at the same time.

Picture of an Execution

Machine Cycle Time = time for one cycle

Drawing of Cycles. Actually, sine wave

Clock Speed (Table 3.1) - rate at which CPU produces pulses. Slide shows historical trend in clock speeds.

Size of memory

One measure of computer power is Wordlength Once as little as 8 bits, now 64 bits. The computer processes, usually, one word at a time. See slide for microcode.

Data are moved about the computer via the Bus Line. Another measure of power is the width of this line.

Moore’s Law (Figure 3.4) The number of transistors that can be put on a chip has doubled every 18 months or so.

This means power doubles roughly every 18 months, cost per bit and cost per CPU cycle halves roughly every 18 months.

RISC In 1966, Seymore Cray designed a chip with 1/3 the number of instructions; it processsed elementary instructions 10 times faster than other chips (but net speed was less than 10 times, because it took more instructions to do the same things.) This is called reduced instruction set computing (RISC) IBM 6000, Apple Power PC are RISC machines. Pentium has lots of instructions, so it can do much more with a single instruction. This is called Complete (or Complex) Instruction Set Computing, or CISC

Computer only knows 1s and 0s; text is just a number. The letter A is, of course, 32 in one scheme, or 43 in another. The number of bits to represent one character is called a Byte and is now 8 bits.

RAM and ROM RAM is Random Access Memory. Volatile (loses all information when power is turned off). Program instructions must be stored in RAM before they can be executed. RAM needs to feed these instructions to the CPU at 500,000,000 per second. Fast memory is very expensive.

ROM is Read only memory. A program in ROM loads the program in secondary storage into RAM, called bootstrapping.

To save money, the instruction that are to go next to the CPU can be stored in a small amount of Cache Memory (Figure 3.6) which is faster than ordinary RAM, and more expensive.

Multiprocessing and coprocessors The computer has more chips, special chips for input and output, etc. Having all work together is multiprocessing.

Parallel Processing (Figure 3.7) uses multiple ALUs under the control of one or more CPUs. Sometimes, separate CPUs work on different parts of the problem and just share memory.

Secondary Storage is needed for permanent storage of programs and data, since RAM, or primary memory, is volatile. Also, RAM is expensive, and secondary storage is cheap.

You need a moderate amount of moderately expensive fixed secondary storage (hard disk inside computer), and a huge amount of removable secondary storage, which is very cheap (floppies, zip disks, optical disks, and tape)

Access Methods and Storage Devices Secondary storage is either sequential access (magnetic tape) or direct access (disks of all types).

Cost Comparisons for Various Forms of Data Storage (Figure 3.8) Prices are a) out of date; and b) wrong. RAM memory is expensive; you need at least 128 MegaBytes today. Speed measured in nanoseconds.

Fixed hard drive costs few hundred dollars for 20 Gigabytes; data retrieved in 5-10 milliseconds. Floppy costs $0.40 for 1.44 Megabytes; Zip disk costs $10 for 250 Megabytes; DVD Optical disks cost few dollars for 17 Gigabytes, data retrieved from floppy, zip, optical in few 100 milliseconds.

Capacities of floppys and optical disks

Input and Output Devices Entry vs input devices; source data automation

Laundry list of possible Input Devices

First source data automation: banks introduced magnetic ink character recognition.MICR Device (Figure 3.14) Banks would be unable to process current volume of checks without MICR. Before MICR, could write checks on anything, processed by hand. Today, banks require MICR checks with source of funds already on check. Operator then types in amount, and account is debited by computer.

Output Devices list of a few

Types of Computer Systems PC, network, midsize, mainframe, workstation. Network was an idea that most software & data would be on network so computer needed no memory; however, applications now need local clients and networks are too slow. Workstation is more powerful than PC, usu. Sun computer. Midsize is usually Compaq Alpha or IBM AS/400. Mainframe are large, for airline reservation systems, e.g., thousands of transactions per second on same database. Supercomputers are for intense computation, once bombs, now weather.

Types of Computer Systems (Table 3.3) Unreadable out of date chart, but look at Table 3.3. in textbook anyway.

Mainframe Computer Manufacturers (Table 3.4) Know the names: IBM, and three others.

Annual Cost of PC Ownership (Figure 3.16)Roughly 10,000 per PC per year, more than 50% for users wasting time trying to do stuff for which they haven't been properly trained. Why? Training would cost more than $5000 per user per year. Calculate ROI.

Multimedia Computer System (Figure 3.17)Lists all the stuff you'd need if you had to buy it all separately - audio, video, codec, etc.

Computer System Architecture = overall structure of computer system hardware. Chip architecture distinguishes Sun from Intel from Apple from mainframe.

Industry Standards in Common Use (Table 3.5) Know PnP = plug and play, SCSI = small computer system interface, MMX, card standards PCM/IA, firewire, USB = universal serial port, etc. (rapidly changing)