Talking about Computer Hardware

Transcription

1 Computer Hardware Hardware components of a computer system The 2 Figure. Talking about Computer Hardware Computer and peripherals Hardware Profiles Profiles show current values for RAM and CPU speed. In the Mac (left) the bus speed is listed as 67 MHz. Bus speed is the rate of communication events in the main bus. It is usually much slower than the processor or CPU speed. The PC (below) has a CPU clock speed of.69 GHz=69 MHz Double Data Rate Synchronous Dynamic Random Access Memory

2 The Power supply Cooling fan The : Looking Under the Hood CD Drive Internal HD drive Expansion bus connector Expansion cards How Modern Computers Represent Data Digital versus Analog Representation digital: high and low power signals analog: continuous variable scale Numbering systems every numbering system has a base Analog Digital Binary Numbers Binary Numbers Binary numbers exercise A binary number is called a binary digit, or bit. A bit is the smallest unit of information that a computer can work with. Number

3 Counting Counting with binary, decimal, and hexadecimal numbers Decimal numbers binary numbers hexadecimal numbers A 0 B 2 00 C 3 0 D 0 E 5 F ASCII & EBCDIC Originally used a total of 7 bits encodes a total of 28 characters included letters, numbers & punctuation Looking for a wider market IBM and Apple expanded to 8 bits extended character sets not standardized Unicode expanded to 6 bits (65,000 characters) can represent most languages ASCII: American standard code for information interchange EBCDIC: Extended binary coded decimal interchange code Units Amount of information Bit, smallest amount of information, or 0 Byte=8 bits KB=2 0 =02 bytes, MB=2 20, GB=2 30 Speed for cycles (CPU and buses) Hertz= cycle per second KHz=000 Hz, MHz=0 6, GHz=0 9! Speed for data transfer (data/time) bps (bits per second) Kbps, Mbps Note that Kbps=(/8) KBps. This is very relevant when you compare prices for internet access. Typical values (Jul 0) Amount of data Hard disk GB DRAM MB Document 0.-0 MB Software 00 MB Cycles and clock CPU Mhz data bus Mhz Bus speed affects ALL components, and it should be considered more consistently when comparing systems. Data transfer rates (these are maximum or burst speeds; average performance can be much slower) IDE 5-0 MBps EIDE (Ultra ATA) 00 MBps Ultra wide SCSI 0 MBps=360 Mbps IDE/ATA is simpler, slower and cheaper than SCSI. SCSI is used for high performance systems that have a lot of disk activity (servers, large databases, digital video, etc.) Motherboard CPU Socket RAM expansion slots expansion card slots Motherboard elements CPU: Central processing unit RAM: Random-access memory BUSES: data and expansion buses Expansion slots: video, SCSI, sound, etc. : parallel, serial, keyboard, mouse, etc. BIOS: Basic input-output system ( ROM chip) CMOS: Complementary metal-oxide semiconductor (!) special memory that stores system configuration How the computer avoids the Clean slate syndrome: each time the computer is turned-off it becomes a memory-less object, except for its BIOS and CMOS. When the power is turned on, BIOS gives the computer basic capabilities and instructions to go to the hard disk and load the information form a specific area (boot area) onto RAM. Once the computer reads the information it learns what it is, what it is supposed to do, and how to do it. The idea of clean slate is shown in the movie of the same name with a humorous approach, and in the movie Memento in a rather dark manner. Both are recommended. 3

4 Motherboard components (998) Motherboard Figure.2 UltraSCSI expansion card Video card ROM chip that contains the BIOS on the motherboard The CPU:Looking Under the Hood System Clock determines speed of the system; the clock ticks at the speed usually advertised for the processor. Each time the clock ticks, the computer performs one step in the processing. Instruction sets list of instructions that the CPU understands These are very basic units of processing of bits CPU s work in a four-step process (machine/processing cycle): fetch instruction from registers or RAM, decode instruction in CPU, execute instruction in CPU, write-back result in registers or RAM. Arithmetic-Logic Unit (ALU) arithmetic & logical operations registers are temporary storage inside the CPU and they work at maximum speed. Figure.7 ROM: Read-Only Memory

5 Processor slots Slot (Pentimu II & Celeron) Socket 7 (Cyrix & AMD) PowerPC G5 Architecture Figure. Figure.3 Detail of a Pentium 3 CPU Comparing CPU s Data Bus Width & Word Size number of bits in bus determines word size 6-bit CPU works with 6-bit word size CISC (complex instruction set computer) many instructions & special-purpose circuits RISC (reduced instruction set computer) bare-bones instruction set less expensive, more efficient The design of CISC and RISC is converging The best way to compare CPU s is to perform benchmark tests in which the actual time it takes the computer to complete a task is measured. This time depends on the joint speed of al elements on the computer system, and is what in the end matters to the user. The fastest computer depends on the task used for the benchmark. Usually, standard tests include CPU-intensive and disk-intensive tasks to get a general idea of global performance. Memory: CPU s s Electronic Scratchpad Memory Capacities kilobyte (KB), megabyte (MB), gigabyte (GB) Random-Access Memory (RAM) store programs & data being used each memory location has an address volatile Cache Memory allows maximum speed L: level cache is in the CPU (32K+32K) L2: level 2 cache is usually backside (52K-M, at half or full processor speed) L3: level 3 cache is very new. DRAM: dynamic random access memory SIMM: single in-line memory module DIMM: double inline memory module Memory technology: DDR SDRAM (synchronous dynamic RAM). Newest & fastest; only in DIMMS DRAM speed is measured in nanoseconds (/,000,000,000 s). Typical speeds are 60 ns and 70 ns (larger number is slower). 5

6 Levels of cache memory in computers with different types of CPUs CPU CPU with L cache CPU with L and L2 cache Bus Bus PC2700 dual in-line memory module (DIMM) L2 Cache L3 Cache Called DDR or double data rate because it can perform two data accesses in each clock cycle. Figure.6 Buses Freeways for Data BIOS and Bus Circuits that carry data from one component to another. The wider the bus, the more quickly the data can flow and Connectors 6

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8 Connectors Interface or Port Type Gigabit Ethernet Fast Ethernet Ethernet 802.a Wireless Ethernet 802.b Wireless Ethernet Ultra ATA/33 Ultra ATA/00 Ultra ATA/66 Ultra ATA/33 Ultra 320 SCSI Ultra 60 SCSI Wide Ultra2 SCSI Wide Ultra SCSI Fast Wide SCSI SCSI-2 SCSI- IEEE 39 FireWire USB 2.0 USB. Mbps Answer the following questions on your scantron.. T/F. The internet and the web are basically the same thing. 2. How many bytes form an IPv address? A. B. 2 C. D T/F. Most ISP s provide lines that are faster downthan upstream.. T/F. POP allows users to read messages at the server, without downloading them to the client. 5. Select the combination of RAM and CPU speed that could describe a PC today. A. 32 MB & 3 GHz B. 256 MB & 2 GHz C. 256 GHz & 2 MB D. 66 MHz & 6 KB 6. Select the lecture part you liked best. A. Components of B. Digital vs. Analog signals C. Motherboard components D. Memory and Cache 7. Which lecture format did you prefer? A. History of computers B. System unit 8