A+ Core 1 study notes

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40. One good way of determining a bad power supply is that the fan will not rotate. Also, the computer will not boot and the LED s indicating the speed will be OFF.

41. Terminate and Stay Resident programs, as the name suggest, stay inactive in the memory area of the computer. An example of a TSR is Screen saver program. To view, which programs are consuming how much memory area, MEM command can be issued with switch "C".

42. If you notice that the time is constantly incorrect, even after adjusting correctly, the most likely cause is that the CMOS battery has become weak and need to be replaced.

43. When you have two hard disk drives, the following two combinations are possible:

• Install the drives one each on primary and secondary controllers and designate both as Masters.

• Install both the drives on the primary controller and designate one as Master and the other as Slave.

44. Cleaning of PC components – tools used:

Recommended cleaning procedures for various components are as below:

• Computer Cabinet: Use Mild detergent

• Dust inside the computer: Use Compressed air

• Tape drive: Use tape drive cleaning catridge

• Floppy drive: Use Floppy drive cleaning kit

• CD ROM drive: Use CD-ROM drive cleaning kit

• Mouse: Use cotton swab with Isopropyl Alcohol.

IsoPropyl Alcohol is recommended for cleaning PCAs such as motherboards. Mild detergent can be used for cleaning the outside cabinet or the keyboard.

45. Laptop computers:

• Nickel Cadmium battery is not environmentally friendly and not as efficient as Nickel / Metalhydride or Lithium Ion. Nickel / Metal hydride, though environmentally friendly, not as efficient as Lithium Ion. Lithium Ion battery is environmentally friendly and very efficient.

• Passive matrix displays are most commonly used and cheaper than Active matrix displays. Also, passive matrix displays consume less power. However, the advantages of active matrix display are that they can handle faster screen image transition, and display is clearly viewable, even from slant angles.

• Laptops most widely use PCMCIA cards, also referred to as PC cards.

46. Handheld PCs are also referred to as Personal Digital Assistants (PDAs).

47. Batteries, and chemical solvents contain environmentally hazardous chemicals and therefore, should not be disposed through dustbin. Always refer to the manufacturer's instructions or the relevant State guidelines.

48. Given below are important bus types and their characteristics:

49. Printers and cables:

• InkJet is the generic name given for contactless printing using ink.

• The centronics cable, used for parallel printing will have a male DB-25 connector at one end and a female 36 pin connector at the other end.

• Friction feed is most commonly used with laser printers, and Inkjet printers.

50. Ethernet:

• 10BaseT Ethernet complies to IEEE standard 802.3 and requires an RJ-45 connector to connect to the NIC. The maximum specified transmission speed for 10BaseT Ethernet is 10Mbps. For 100BaseT, it is 100Mbps.

• Ethernet is based on CSMA/CD, which stands for Carrier Sense Multiple Access / Collision Detect.

• CAT3, CAT4 or, CAT5 cabling is used with 10BaseT Ethernet. Thin coax is used with 10Base2 Ethernet. Thick coax is used with 10Base5 Ethernet. FDDI uses Optic Fiber as the medium.

• 10Base2 network, also known as Thin-net, uses BNC connector to connect to the NIC.

• A repeater can extend the distance over which the signal can travel without loosing out due to attenuation.

• The maximum length of the cable for 10BaseT Ethernet segment is 100 meters.

• Thin co-axial and thick co-axial cables have conductive grounding sheath surrounding the center conductor. Therefore, the electromagnetic interference (EMI) is significantly less.

51. Token Ring supports 4 Mbps and 16 Mbps speeds.

52. NIC, Network Interface Card is the one that interfaces your PC to the LAN. NIC sits in your PC on one of the slot available on the motherboard.

53. Ultra IDE cable has 80 wires, and handles better speeds compared to IDE cable with 40 wires. The additional wires are introduced to reduce noise and thereby improving speed.

54. When signals are transmitted over long distance, there will be ohmic losses, which result in loosing the strength of the signals. This is known as attenuation. Amplification is opposite of attenuation.

55. Asynchronous serial communication uses Start bit/Data bits/Stop bit. A modem connecting to the Internet is a typical asynchronous device. Synchronous communication uses clock signals to transfer information. Does not use start/stop bits. Synchronous communication is normally used for high speed data transfers.

56. USB:

• USB supports up to 127 devices simultaneously.

• USB enables you to daisy chain up to 127 USB devices. A USB hub is used for this purpose.

Also, USB devices can be plugged in without turning on/off power. I.e. USB devices are hot swappable.

57. A floppy cable will have 34 wires, and the wire with red stripe signifies wire going to pin number 1 of the connector.

58. The Slot 1 package replaces the Socket 7 and Socket 8 used by previous Pentium processors. Slot 1 is a 242-contact daughtercard slot that accepts a microprocessor packaged as a Single Edge Contact (SEC) cartridge. A motherboard can have one or two Slot 1s. More recently, Slot 2 package has been developed and used by recent processors.

59. The following are major characteristics of a floppy drive:

• The ribbon cable connecting the floppy drive to the mother board, is 34 wires wide.

• There can be a maximum of two floppy drives in a PC

• The floppy ribbon cable is distinguished easily from that of an IDE cable by a small twist in the cable. The purpose of the twist is to differentiate between floppy drive A and floppy drive B.

60. TCP/IP is the medium of transport when your are accessing the Internet.

61. ISDN: ISDN BRI (Basic Rate Interface) will have two B channels, each can carry data up to 64Kbps, aggregating to 128 Kbps.

62. ATX power supply provides three different voltages: 3.3Volts, 5Volts, and 12Volts.

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