DC2004, Chapter 4 Checkpoint Solution

1. (d) adapter cards
2. (e) processor
3. (b) memory chips 
4. (c) memory slots
5. (a) expansion slots

System Bus Specifications: http://www.sollae.co.kr/~mhyun/interest/bus/bus.html 

1. (c) On mobile devices, the display often is a part of the system unit.
2. (a) An integrated circuit (IC) contains microscopic pathways capable of carrying electrical current. [This is true, but does not characterize what an IC is.  A much better definition:  An integrated circuit is a circuit with multiple active and passive components inseparably associated on a chip to perform the functions of the circuit.]
3. (b) Logical operations include conditions along with operators such as AND, OR, and NOT.
4. (c) Processors that use pipelining are faster because they do not have to wait for one instruction to complete the machine instruction cycle before fetching the next.
5. (b) The higher the clock speed, the faster the processor, and more expensive the computer. [The cost to produce might be more expensive if investment in new production methods or facilities is required. The sale price is a marketing consideration.  It is possible that an increase in speed does not produce an increase in sales price if competitors also produce a comparable processor.]
6. (a) (Extended) ASCII is the most widely used coding scheme in the Western world by most personal computers and mid-range servers.  As Oriental computing continues its rapid expansion, UNICODE will become the most widely used coding scheme.
7. (d) Memory stores all of: the operating system and other system software, application programs that carry out specific tasks, and the data being processed by the application programs.
8. (a) A kilobyte (kB) of memory is equal to exactly 1,024 (2¹⁰) bytes, but often is rounded down to 1,000 bytes [through ignorance]. [You should not do this.]
9. (d) A Dual Inline Memory Module (DIMM) is a type of memory module with pins on opposite sides of the circuit board that connect together to form a single set of contacts.
10. (d) Many of today's computers support Plug and Play which means the computer automatically can configure adapter cards and other peripherals as you install them.
11. (c) A parallel port sometimes is called a Centronics interface, after the company that first defined the standard for communications between the system unit and a printer. [A Centronics port is a particular type of printer parallel port. There are other types of parallel ports. Centronics connectors and cables are good, but they also are unreasonably expensive. A USB-II device should out-perform a Centronic device.]
12. (d) Word size is the number of bits the processor can interpret and execute at a given time. [It is common that a processor will have the ability to use several different size of words.]
13. (a) The most common and slowest expansion bus is the Industry Standard Architecture (ISA) bus.
14. (d) Hard disk drives usually are installed in internal bays.

1. (e) chassis: Metal or plastic case that protects the internal components of the system unit.
2. (h) microprocessor: Term used by some manufacturers to refer to a personal computer processor chip.
3. (a) superscalar: Processors that can execute more than one instruction per clock cycle.
4. (d) coprocessor: Additional processor chip or circuit board that assists in performing specific tasks.
5. (i) Unique number that identified the location of a byte in memory.
6. (c) memory module: Small circuit board on which Random Access Memory (RAM) chips usually reside.
7. (g) microcode: Type of instructions used to program a Programmable Read Only Memory (PROM) chip. [Some processors implement its instruction set by use of a much faster processor that interprets a machine language instruction as a sequence of microinstructions.  These microinstructions are called microcode. The IBM 360 is the first major example of using this type of architecture.][The code used to program a microprocessor is not necessarily microcode.  Processors are programmed.  Programs are stored.  In the example of this question, the code is stored in a Programmable Read Only Memory (PROM).  Calling a ROM "Programmable" merely means its contents can be established after the ROM has been manufactured.  This involved use of a device, often called a "Programmer".  The PROM does not care what is stored, instructions or data. The PROM does not execute anything.]
8. (j) synthesizer: Peripheral or chip that creates sound from digital instructions.
9. (f) expansion bus: Allows the processor to communicate with peripherals.
10. (k) bay: Opening inside the system unit in which additional equipment can be installed.

1a. What is the system clock?

The system clock is a small quartz crystal and associated circuit used to control the timing of all computer operations on a microcomputer.  Main frame computers have a separate clock for the CPU, and the CPU operates asynchronously with the rest of the computer.

1b. How does clock speed affect a computer's speed?

If the clock speed on a particular computer is increased, the timing signals will increase in frequency.  As long as the clock speed is not faster than the maximum propagation delay of signals in the computer, the computer will act satisfactorily, and therefore the speed of the computer will increase.  If the speed of the clock is increased a little too much, the computer will effectively slow down due to having to handle error conditions and retransmission of data due to bad parity checks.  As speed of the system clock continues to increase, the computer becomes inoperable.  A computer is designed as a whole system.  All the components must be able to work together.  Merely increasing the clock speed does not necessarily result in faster system performance.  When considering an accelerator board or increasing the clock speed, be sure to check the technical documentation of the system motherboard and vendor application notes.

2a. How are a chip-for-chip upgrade, a piggyback upgrade, and a daughterboard upgrade different?

2b. What is a zero-insertion force (ZIF) socket?

The purpose of a zero-insertion force socket design is to reduce pin damage to the chip.  A ZIF socket has a lever that applies a force upward over an area in the center of the processor chip to raise the chip evenly out of its socket.  Newer ZIF sockets further reduce the force required by having a locking panel that releases sideways compression on pins before lifting motion is applied.

3a. How is dynamic RAM different from static RAM?

3b. Why are synchronous DRAM, Double Data Rate SDRAM, and Rambus DRAM chips faster than basic DRAM?

For a very good review of memory technology, see http://www.pctechguide.com and click on System Memory.

4a. What is memory cache?

Memory cache is high speed temporary storage located between primary storage and the CPU and used to preposition data and instructions closer to the CPU for rapid access.

4b. How are the three types of cache (Level I, Level II, and Level III) different?

Cache levels differ primarily in proximity to the CPU and the complexity of circuitry associated with the particular cache.  The idea is to migrate instructions and data from inexpensive large capacity slower storage to much faster storage so that they are available without delay to the CPU when actually needed.  This involves predicting what will be needed in the future and choosing a pre-positioning strategy that will maximize overall system performance.

L1, L2, L3 only indicate the logical nearness of a cache to the CPU.  L1 is closer, and usually more sophisticated in design, than L2.  Similarly, L2 is closer, and possibly more sophisticated in design, than L3.  Usually, increased number of levels of cache, and increased cache sizes are accompanied by appropriate designs that result in increased overall system performance with successive generations of chip designs.

Other terms describe the design properties of a cache.

IA-32 Intel Architecture Software Developer's Manual, Volume I: Basic Architecture
Introduction to Microarchitectural Optimization for Itanium® 2 Processors: Reference Manual
Andrew S. Tanenbaum, Structured Computer Organization, Third Edition, Prentice Hall (1990), Pages 209-215.

5a. How are male connectors different from female connectors?

5b. What is a gender changer and when would it be used?

1.  a.  What is the purpose of the CPU?

    Answer The central processing unit (CPU) interprets and  carries out the basic instructions that operate a computer.

1.b.  What is the control unit's job?

    Book answer: The control unit interprets each instruction issued by a program and then initiates the appropriate action to carry out the instruction.

    This is not the same as the translator called an interpreter.  

    The control unit issues the timing and control signals.  It includes a system clock, which is used to generate timing signals for the rest of the computer.  It includes interrupt signal lines.  The control unit uses logic gates to decode an instruction and to initiate the control signals needed to carry out the instruction.  It is common for sophisticated processors to use a sequence of microinstructions to implement instructions.  

1.c.  What are the for basic operations?

    Answer: The four basic operations are: Fetch, Decode, Execute, and Store.

2.a.  How is instruction time, or I-time, different from execution time, or E-time?  [buzz...]

    Answer:  The text defines Instruction time (i-time) as the time for fetch and decode.  The text defines Execution time (e-time) as the time for execute and store.

    I have not heard of the terms "I-time" and "E-time" before looking at this book.  The far more common terms are "fetch time" and "execute time".

Mark Minasi, The Complete PC Upgrade & Maintenance Guide, Sybex (2000) pages 96-97, uses the breakdown: fetch, decode, get the operands, execute, write back results. It does not attempt to group these together.

Rodnay Zaks, Programming the Z80, Sybex (1980), pages 55-56, uses the breakdown: fetch, decode, and execute.  The fetch cycle is discussed separately.  The decode and execute cycles are discussed together.

Martha E. Sloan, Computer Hardware and Organization, Second Edition, Science Research Associates (1983), uses only the two states: fetch and execute.

Roger L. Tokheim, Microprocessor Fundamentals", Schaum's Outline Series, McGraw-Hill (1983), page 81, uses the categories: fetch, decode, and execute.

    An instruction cycle often requires multiple machine cycles to complete its task.  Variable-length instruction machines require variable number of machine cycles per instruction.  A machine cycle consists of multiple clock cycles to accomplish the simplest elementary operation.  On simple or old machines, a machine cycle was a clock cycle.  Things got more complicated when IBM introduced the concept of microcode on the IBM360 for defining machine language instructions.  Specific details are machine-dependent.  Pipelining is possible because of the multiple cycles needed for instruction execution, by overlapping the stages of execution of instructions.  This does not decrease the overall time required to execute a specific instruction, but it does allow an increase in the average rate of instruction completion.

2.b.    In what unit is a computer's speed measured?

    In the professional computer world, a more meaningful measure is MIPS (millions of instructions per second).  This is an average since instruction time varies depending on which instruction is being executed.  On computers used for science and engineering calculations, MFLOPS (millions of floating point instructions per second) is the preferred measure.  In practical evaluations, people run programs typical of the nature and mix of programs they intend to use the machine for.  Standardized programs used for testing purposes are called "benchmarks".  Results are recorded for a variety of machines and operating systems and compared.

    Components in a computer operate at different speeds, with control cycles usually keyed to an integer multiple of the system clock cycle.  The basic limiting factor affecting system design is memory chip speed.  On personal computers, this is commonly 100 MHz or 133 MHz.  Memory can be partitioned into memory banks to increase system speed by permitting different parts of memory to be accessed nearly simultaneously.  For example, a two-bank memory can have all odd addresses assigned to one memory bank and all even addresses to the other memory bank.

3.  How are arithmetic operations, comparison operations, and logical operations different?

Answer:  

4.a.  What are some of the different processors used in today's personal computers?

    General comment: Miniaturization and manufacturing circuits on a common chip increases reliability and speed, and decreases overall power consumption.  The trend is to pack as much onto one chip as possible.  Many features that existed on separate cards or on a motherboard are being migrated into the same package as the processor.

    Critical technologies are materials science, line width, number of chip layers, and materials science.

4.b.  What is a new type of processor?

    A new type of personal computer processor, called an integrated CPU, combines functions of a processor, memory, and a video card on a single chip.

5.  How are components different among a desktop computer, a notebook computer, and a handheld computer?

1. DRAM (dynamic RAM): (b) Type of memory that must be re-energized constantly or it loses its contents.
2. SRAM (static RAM): (g) More expensive type of memory that can be re-energized less often; used for special purposes.
3. SIMM (single inline memory module): (a) Circuit board with RAM chips on only one side.
4. DIMM (dual inline memory module): (e) Circuit board with RAM chips on both sides.
5. RAM cache (or memory cache): (d) Speeds processing time by storing frequently used instructions and data.

1.b.  What are registers?

Answer: The CPU uses temporary storage locations, called registers, to hold data and instructions. A microprocessor contains many different types of registers, each with a specific function.  These functions include storing the location from where an instruction was fetched, storing an instruction while it is being decoded, storing data while the ALU (Arithmetic / Logic Unit) processes it, and storing the results of a calculation.

4.  What are some special-purpose port used in many of today's computers?  For what purpose is each port used?

MIDI Port:  Musical Instrument Digital Interface.  This is an interface standard.  Learn a little more at http://nuinfo.nwu.edu/musicschool/links/projects/midi/pages/stmidifi.html .  Get some of the technical details at http://www.music-center.com.br/spec_smf.htm .

SCSI Port:  Small Computer System Interface.  Learn more about upgrading the SCSI standards at http://www.zdnet.com/products/stories/reviews/0,4161,278589,00.html .

IEEE Standard 1394 Serial Port Specification (Texas Instruments P1394, Apple's FireWire): Learn more at http://www.ablecom.net/users/onspec/html/ieee_1394_port.html .  

For short distances (less than 15 m), the parallel port approach will give better performance for fast data transfer than a serial port.  If a serial port is good, a parallel version will be even better.  For long distance, parallel transmission has a problem of synchronizing the arrival of bits.  One transmission path may be very different in length than another path, requiring a different transmission time.  This can cause bits from one transmission to arrive about the same time as bits from another transmission that travel on a different path.  In this case, serial transmission is better.

IrDA Port:  Learn more from the Infrared Data Association at http://www.irda.org/standards/specifications.asp .

5.a.  How is a system bus different from an expansion bus?

There are 3 major bus types: the CPU bus, the address bus, and the data bus.  These are not necessarily the same path width.

The CPU bus transfers data between components of the CPU, such as between the accumulator and registers.

The address bus transmits addresses between the CPU's program counter, address register, and the memory address registers.

The data bus transmits data between the CPU and the memory buffer register of main memory and other devices.

The text's system bus corresponds to the combination of the address bus and the data bus between the CPU and memory.  These are separate functions.  They can be (and often are) different widths.  They may be carried over the same bus if the information is multiplexed onto the bus.  The architecture of a system can establish different buses to match speeds and maximize overall system throughput.  It is a tradeoff of cost and performance.

An expansion bus connects expansion slots to the system's data and control signal buses.

5.b.  How is an internal drive bay different from an external drive bay?

A bay is an open area inside the system unit used to install additional equipment.  An external drive bay allows access to a drive from outside the system unit.  Removable media disk drives are mounted in external drive bays.  An internal drive bay cannot be accessed from outside the system unit.  Hard disks are usually mounted in internal drive bays.