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• Two basic types of motherboards: AT (Advanced Technology) and XT (Extended Technology). Baby AT and ATX are form factors of the AT system board.
  
  
• Two basic expansion buses: ISA and PCI. ISA is the Industry Standard Architecture used on XT and AT boards.
  
  
• XT boards use an 8-bit ISA bus. In general, AT boards use a combination 8-bit/16-bit ISA bus.
  
  
• ISA bus slots are usually very long and large, and tend to be nearer one of the edges of the motherboard.
  
  
• PCI bus is a 32-bit/64-bit bus specification with smaller slots, generally nearer the center of a motherboard.  PCI slots can sometimes be interwoven between the ISA slots; first ISA the PCI, then ISA again, and so forth.
  
  
• CMOS is a battery-backed chip that contains system settings, configured from a hotkey combination at startup.  CMOS stores passwords.  The best way to recover from a forgotten CMOS password is to disconnect the chip's power supply, thereby clearing all settings.  A badly configured CMOS (where the hardware attached is set with the wrong name) usually means a device mismatch error.
  
  
• Jumpers are used to set the motherboard's clock speed.  The clock oscillator can be tuned to a specific frequency.  One Hertz (Hz) is the time it takes for the oscillator to produce one full wave.  One Megahertz is one-million cycles (clock ticks).  Motherboard speeds should match the fastest CPU speed.
  
  
• Power supplies take in 110 volts (AC) and typically put out 12 and 5 volts (DC).  Sometimes a voltage regulator on the system board can be set by jumpers to provide other voltages (note the 3.3 volts used by many processors).
  

• Real mode comes from the 8088/86 processor where the chip can only address 1 MB of real memory addresses.  The 1 MB is called "conventional memory" and can be split into low memory (IRQ tables), application memory (640 K), and high memory (Around 370 K).
  
  
• Protected mode started with the 80286 processor and means that one application can run in a different area than another application, and they won't affect each other if one of them crashes.
  
  
• Enhanced mode (386 Enhanced mode, 32-bit Protected mode), comes from the 80386 chip.  All current processors can use Enhanced mode.  The 32-bit 386 was the first chip that could run both Real mode and Protected mode, without resetting the system.
  
  
• Parity is a way to test RAM chips (SIMMs and DRAM) to see if they can correctly remember data.  Parity checking requires an additional circuit and login in order to work.  When a computer heats up it can change the SIMMs and cause parity errors.  The POST routine can't uncover heat-related problems since everything on the board is cool.  Heat problems usually cause software problems and are uncovered using software utilities.
  
  
• Pentium chips generally run from 66 to 200 MHz.  Pentium Pro chips are usually sold in two speeds:  180 MHz and 200 MHz.
  
  
• L1 cache (Level 1) is internal to the CPU and is usually 16 K in size.   L2 cache (Level 2) is an external chip or chips near the CPU and works best when it is 256K or 512K in size.
  
  
• HIMEM.SYS is a memory manager required by Windows 95.  Without HIMEM.SYS, the system can't access any more than the 1MB of conventional memory.   HIMEM.SYS is loaded from the CONFIG.SYS file in everything except Windows 95, which loads it from IO.SYS.
  

PERIPHERALS:

• Port connectors from the back panel of a chassis include: 9-pin male serial, 25-pin female parallel, 15-pin female video.
  
  
• Parallel cables are usually a DB25-pin male (plugs into the female end on the chassis) connector with a 36-pin male Centronics connector at the other end.
  
  
• SCSI cables are usually 50-pin ribbon cables.  SCSI chains can have up to 7 devices and must be terminated at both ends.  IDE chains can have 2 devices.   SCSI is usually used for external devices like CD-ROM drives and scanners.
  
  
• COM1 and COM3 are logically joined, while COM2 and COM4 are logically joined.  COM1 and COM3 use IRQ4 while COM2 and COM4 use IRQ3.
  
  
• COM port addresses include: com1=03F8; com3=03E8; com2=02F8; com4=02E8
  
  
• LPT1 uses IRQ7, and LPT2 uses IRQ5.
  
  
• IRQ14 is the primary drive controller, and IRQ15 is the secondary drive controller.   When IRQ2 cascades to IRQ9, number 2 can't be used.
  
  
• Laser printers use a primary corona wire to charge the drum.  The drum is cleaned, charged, and written to.  The image develops (by the corona charge) and pulls toner to the drum.  Paper is charged and pulls toner from the drum, where it's fused by the fuser rollers.  If the heat-sensor on the fuser shuts down, the toner will fail to stick to the paper.  Paper jams are usually caused by a bad separator pad.
  
  
• Sectors are 512 bytes.  Clusters grow to fit the size of the formatted logical drive, depending on the operating system.  The FAT is 16K.  The master boot record is in Sector 0, Track 0, Head 0, Cylinder 0 of the primary active partition.
  
  
• Hard drives can have a maximum of 24 logical drives (A: and B: are floppies; C: is drive 1).  Once the C: drive has been partitioned, the largest extended partition can have 23 drive letters.
  
  
• LASTDRIVE must be set for any number beyond the default E: drive.
  
  
• If a keyed connector doesn't have physical notch, the red stripe refers to Pin 1.
  

DOS:

• FDISK.EXE is used to create partitions.
  
  
• Format c: /S transfers the system files to the C: drive.
  
  
• SYS C: (SYS.COM) is used to transfer system files to a corrupted disk showing "Missing or bad system files" errors.
  
  
• An operating system is a command line, a command interpreter (processor, COMMAND.COM), and a user interface.  The three critical DOS (system) files are IO.SYS, MSDOS.SYS, and COMMAND.COM (in that order).
  
  
• DOS loads as follows: ROM BIOS, POST, IO.SYS, CONFIG.SYS, MSDOS.SYS, COMMAND.COM, AUTOEXEC.BAT.  Windows uses almost the same order, except for the AUTOEXEC.BAT batch file.
  
  
• CONFIG.SYS loads Real mode device drivers (DRIVERS= ).  AUTOEXEC.BAT executes user commands automatically at startup.  Device drivers usually have a .SYS extension.
  
  
• ATTRIB.EXE is used to set file attributes such as Hidden, Read-only, System, Archive.  The Hidden attribute prevents accidentally deleting a file.
  
  
• Wildcards are * and ? where * finds any number of characters to the right and ? finds only one character per question mark.
  
  
• MD is the same as MKDIR.  CD is the same as CHDIR.  REN is the same as RENAME.  DEL is the same as ERASE.
  
  
• MEMMAKER.EXE is a way to optimize upper memory (UMB) and high memory.   MEMMAKER doesn't speed up a system.
  
  
• DEFRAG.EXE is a way to move parts of files (clusters) next to each other and speed up access times on a hard drive.
  
  
• SMARTDRV.EXE is a software cache for reading hard drives.  Windows 95 removes SMARTDRV from a CONFIG.SYS file by placing a REM (remark) at the beginning of the line.
  

Windows 3.X:

• Windows 3.x can run on a 286, but can only run in Enhanced mode with a 386 chip or better and a minimum of 2MB of RAM.
  
  
• Core files are: USER.EXE, GDI.EXE, KRNL386.EXE.  GDI is the acronym for graphics device interface.
  
  
• Swap files can be permanent (386PART.PAR) or temporary (WIN386.SWP).  They are managed in the Control Panel under the Enhanced choice.
  
  
• WIN.COM starts Windows.  Then SYSTEM.INI (device drivers and program configuration) and WIN.INI (user options and environment configurations) begin.   WIN.INI is not necessary, but it is created if it doesn't exist.
  

Windows 95:

• Windows 95 requires a 486 chip or better and a minimum 4MB of RAM.
  
  
• Registry files are SYSTEM.DAT and USER.DAT.  They can only be edited with REGEDIT.EXE.
  
  
• Windows 95 loads IO.SYS, CONFIG.SYS, and MSDOS.SYS.  HIMEM.SYS must also load from MSDOS.SYS; otherwise, Windows 95 won't start.
  
  
• Safe mode loads VGA drivers and keyboard drivers, but no network drivers.  F8 interrupts the startup, providing for a text startup menu of choices.  F4 loads a previous version of DOS.
  
  
• WINS means Windows Internet Naming Services.  10baseT is "twisted pair" wiring.  The "10" represents Mbps.  In 10base2, the "2" equals 200 meters (cable length).
  
  
• An email address such as jimjones@jamesjones.com requires a user name (jimjones) and a domain name (jamesjones.com).  Email uses the Internet TCP/IP networking protocol.
  
  

TROUBLESHOOTING / CONFIGURATIONS:

• Dot matrix print heads come in 9-pin and 24-pin versions.
  
  
• A "good" circuit shows 0 Ohms on a multimeter.
  
  
• EMM386.EXE is an expanded memory manager and is never used in Windows 95 (commented out).
  
  
• ESD is electrostatic discharge.  EMI is electromagnetic interference.
  
  
• Following a blackout, a power surge can blow out the system.
  
  
• The acronym for dots per inch is dpi (printers and scanners).  Pixels are "picture units" and measure graphics resolutions.  Standard VGA is 640x480x16 colors.
  
  

CUSTOMER SERVICE:

Think of a place where you've received excellent customer service.  Then think about what it would be like if you had a very important appointment right after you left that place and couldn't afford to be late.  The way you were treated, and the worries you would feel are the key to answering the Customer Service questions.