A+ Core hardware Technologies  -Exam cram

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31. Uninterrupted Power Supply (UPS):

An UPS is desired to be purchased for any critical and un-interrupted use of computers. It has the following benefits:

1. Provide protection against small surges

2. Filters noise from entering the computer

3. Provide power to the computer during line power failure

4. Give stable power to computer, even when the line power is unstable.

Note that the UPS can give un-interrupted power only for a fixed amount of time under a given load, in the absence of line voltage.

32. The following are types of PCMCIA (PC cards) cards:

1.      Type I: 3.3 mm thick. Used for memory upgrade cards.

2.      Type II: 5 mm thick. Used for modem and network cards. Some are combination Modem/NIC cards.

3.      Type III: 10.5 mm thick. Used in PC card hard drives

33. Computer Cache Memory:

Level 1 cache is internal to the processor, and level 2 cache is external to the processor, it resides on the motherboard. In case of Pentium II, L2 cache is built into the cartridge.

34. CPUs and features:

Processor	Socket type	Register	Data Bus	Address Bus
8088	DIP	16 bit	8 bit	20 bit
80286	LLC/PGA/PLCC	16 bit	16 bit	24 bit
80386SX	PGA	32 bit	16 bit	24 bit
80386DX	PGA	32 bit	32 bit	32 bit
80486SX	PGA	32 bit	32 bit	32 bit
80486DX	PGA/SQFP	32 bit	32 bit	32 bit
Pentium	Socket 5 SPGA/ Socket 7 SPGA.	64 bit	64 bit	32 bit
Pentium Pro	Socket 8 SPGA	64 bit	64 bit	32 bit
Pentium II	SEC  Slot 1
Pentium III	SECC-2 / PPGA or FC-PGA

CPU models 80486SX, and above contain on board cache memory.

Pentium Pro and above have onboard L2 cache.

35. Bits and Bytes:

1 KB = 1024 bytes

1 MB = (1024 X 1024) bytes

     = (1024X 1 KB) bytes

     = 1,048,576 bytes

1 GB = (1024 X 1024 X 1024 )bytes

     = (1024 X 1 MB) bytes

     = (1024 X 1024 X 1 KB) bytes

     = 1,073,741,824 bytes

KB stands for Kilobyte

MB stands for Megabyte

GB stands for Gigabyte

Byte is represented by "B" as in MB

Bit is represented by "b" as in kbps

One byte is 8 bits

36. Printer parallel ports come in the following varieties:

1.      Unidirectional: Here, the data travels only from the computer to the peripheral (printer) device.

2.      Bi-directional: Here, the data travels both from the computer to the peripheral device and vice-versa.

3.      ECP (Extended Capability Port): ECP mode offers bi-directional data transfer, as well as DMA for data transfer.

4.      EPP (Enhanced Parallel Port): In addition to bi-directional features, it offers an extended control code set.

37. Laser printers:

·         The following are the 6 steps in the ElectroPhotographic (EP) print process of Laser Printer:

1.      Cleaning: Cleaning the photosensitive drum includes residual toner left on the drum and removing the electrical charges left out on the drum. The physical cleaning is done with a rubber blade and the electrical charge cleaning is done with erasure lamps.

2.      Charging: The next step in printing, is to charge the photo sensitive drum with high negative charge, this is done with the help of a corona wire.

3.      Writing: A laser (type 3) sweeps the entire length of the drum, creating the static image of the matter to be printed. The places where the laser travel, the highly charges are neutralized. Other places of the drum, it remains highly negatively charged.

4.      Developing: Now drum gets in close proximity to the toner. Because the toner is negatively charged, it gets attracted to the areas where the drum is neutral. It will not be attracted to the places where the drum is highly negatively charged. Thus the image of the page to be printed formed on the photosensitive drum.

5.      Transferring: Now, the toner on the drum gets attracted toward the paper, by using highly positive charges developed on the surface of the paper. The "transfer corona" is used to generate highly positive charge on the paper surface and to attract the toner from the drum. Thus the image of the page to be printed formed on the paper. But still, the toner is loose and can get easily smeared.

6.      Fusing: In order to permanently bond the toner particles to the paper, the paper is passed through rollers. One of the rollers, the non stick roller is heated by a high intensity lamp, generating the heat necessary to bond the toner to the surface of the paper.

  ·         Some of the frequently encountered problems using laser printers and probable causes are as given below:

1.      Speckled pages: The causes for this may be a. The failure to clean the drum after printing properly, or b. The drum might have developed scratches.

2.      Blank pages: The causes for white pages may be, A. The toner would have dried out, replace the toner. B. The transfer corona, that is responsible for transferring the toner to the drum might have failed. C. The High Voltage Power Supply (HVPS) failure will also result in white pages.

3.      Ghosted Images: Ghosting occurs when previously printed pages are printed again, though much lighter than the present image. The most likely cause is that the erasure lamp might not be working properly, thus leaving some charges representing the earlier image  left on the photosensitive drum before new image is written. Also check the cleaning blade, which is responsible for scaping the residual toner.

4.      Smudged images: If the fusing fails, the toner will not bond with the paper. Check the halogen lamp responsible for heating.

38. Impact printers are capable of printing multipart forms, since they can give necessary impression to print to multiple forms simultaneously. ECP (Extended Capability Port) has less control overhead and best suited for transferring large chunks of data, such as between the computer and laser printer.

39. The interface cables used widely have the following pin count:

1.      floppy-34 pin,

2.      IDE-40 pin,

3.      SCSI-50 pin,

4.      SCSI Ultra wide-68 pin

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.