Difference Between 8 bit ISA, 16 bit ISA and EISA

Characteristics	ISA( 8 Bit)	ISA (16 Bit)	EISA
Acronym for	Industry Standard Architecture	Industry Standard Architecture	Enhanced Industry Standard Architecture
Introduced In	1981	1984	1988
Introducer	IBM	IBM	Group of Nine Computer manufacturing Companies Led by Compaq(AST Research, Compaq Computer, Epson, Hewlett-Packard, NEC, Olivetti, Tandy, WYSE, Zenith Data Systems)
Data Bus	8 Bits	16 Bits	32 Bits
Address Bus	De-multiplexed 20 Bit address Bus	24 Bit Address Bus	32 Bit Address Lines
Memory Addressability	1.048576 MB	Up to 16 MB	Up to 4GB

SCSI-1,SCSI-2,SCSI-3

SCSI (Pronounced as Skuzzy) is an Acronym for Small Computer System Interface. It is a set of standards for connecting and transferring data between Computer and Peripheral devices. It was developed by Shugart Associates Company in 1981 as a universal and intelligent disk drive interface.

This Interface is generally used for connecting Hard Disk Drives and Tape Drives but can also be used to connect wide range of other devices. This Interface is derived from Shugart Associates System Interface (SASI pronounced as sassy). SASI Controller works as bridge between Disk Drive’s Low level interface and Host Computer. Larry Boucher is considered to be the father of SASI and SCSI. Up to February 1982, ANSI developed this specification as SASI and “Shugart Associates System Interface”. Committee documenting this Standard did not allow it to be named after a company name and after a full day discussion named as SCSI (Small Computer System Interface).

How to Test Power Supply (SMPS)?

Power Supply is the most important part of your computer System because you can not work until your computer is not powering on.  Here I am describing some techniques that you can use to troubleshoot and overcome the SMPS Problems.

Functions Performed

Following Functions are provided by the SMPS (Switch Mode Power Supply):
Its main function is to provide required DC voltage to operate all components in the system.
Different Voltage levels obtained from same power supply.
Output is not affected by the input means if input voltage is between 120V AC to 240V AC the output obtained will be constant. It also provides electrical protection to all components from under voltage or over voltage.
It Provides Necessary Cooling to its components and protects computer from overheating. 

Voltage Levels
If you want to test SMPS than you should know voltage level on every pin of the connector so that testing can be performed:

24 PIN ATX Connector
SIDE A			SIDE B
Pin No.	Color	Voltage Level	Pin No.	Color	Voltage Level
1	Orange	+3.3 Volts	13	Orange	+3.3 Volts
2	Orange	+3.3 Volts	14	Blue	-12 Volts
3	Black	Ground	15	Black	Ground
4	Red	+5 Volts	16	Green	PS_ON
5	Black	Ground	17	Black	Ground
6	Red	+5 Volts	18	Black	Ground
7	Black	Ground	19	Black	Ground
8	Grey	Power good	20	White	NC
9	Purple	VSB  +5V	21	Red	+5 Volts
10	Yellow	+12 Volts	22	Red	+5 Volts
11	Yellow	+12 Volts	23	Red	+5 Volts
12	Orange	+3.3 Volts	24	Black	Ground

 Fig Given Below illustrates these pins on Connector

8 Bit Industry Standard Architecture(ISA) or PC Bus

ISA (Industry Standard Architecture) was first used with the IBM PC in 1981. It was the first open system for PC architecture. No restriction was put on the use of this interconnection method by the IBM. IBM offered free licensing of this PC architecture technique which resulted in more popularity of this. Some main features of 8 bit ISA are:

1) It was introduced by IBM and was the first open system for PC architecture.
2) It provides data transfer rate up to 4.77 Mbps.
3) ISA interface contains 62 pins to interface add on cards. These 62 pins are arranged in two rows, each containing 31 pins.
4) Distance between each pin is 0.1 Inches.
5) 8 Bit ISA make use of Following signals:
    3 Ground Signals
    2 +5V DC Supply
   +12,12,-5V DC supply
    Bidirectional 8 bit data Bus.
   20 Address line, hence memory address space of 1MB (2²⁰=1MB)
   3 DMA request lines
   3 DMA acknowledge lines.
   Six Interrupt Support

Table given below illustrates all signals used by this connector along with their functions:

Functions of North Bridge

After CPU North Bridge is the core chipset on the computer motherboard that controls data communication between CPU and Motherboard. It runs at full processor speed. It mainly works as Memory controller and System Controller. It incorporates interface between Processor and rest of motherboard components.

Chipset is actually numbered according to the number of North Bridge. Nvidia GeForce 320M is a Northbridge /Southbridge fabrication in a single chip. Following are some major functions that are performed by the North Bridge:

Processor Support: Chipset is the major decider on the motherboard that decides which processor is supported, of what speed and how many processors are supported? Following areas are covered by North Bridge under this:

CPU Interface Socket Type: North Bridge is interfaced with the processor through host processor bus and CPU socket. No. of processor sockets are available in the market for this purpose such as Socket 7,Socket -1, Socket A etc. This socket number is decider that which particular Processor class is supported on that motherboard.

Functions of South Bridge

South Bridge is a chipset that is used for controlling I/O Functions such as USB, disk interfaces, PCI Bus, Super I/O Chip support etc. In other words it works as peripheral controller. The main feature of Southbridge is that same South Bridge can be used with different types of North bridges. It is generally located at the lower edge of the motherboard.

Following are some Major Functions Performed by South Bridge:

I/O Control: South Bridge is the key point that decides which kinds of buses, at what speed, and which features will be supported by the system. South bridge controls PCI and ISA buses and transfers information to them or from them.

USB Ports Control: USB Support on the motherboard is provided by the south bridge and which is the main interface for mostly peripheral devices.

Bus Bridge Support: Two main type of buses ISA and PCI are used in most of the modern computers. Since, there is a great speed mismatch between them. South Bridge provides the feature of connecting these two dissimilar buses. This is achieved by PCI-to-ISA bridge chip.

Overclocking

Operating a Chip at higher clock speed than its rated clock speed is called Overclocking. CPU Clock speed is the product of FSB (Front Side Bus) Clock and clock multiplier. Overclocking is achieved by either increasing FSB Clock or Clock multiplier or either by increasing both.

Need of Overclocking

The idea behind the use of Overclocking concept is to increase the system performance at no cost or very little cost. We can Overclock a processor by just changing some settings on motherboard or in CMOS setup. The main considerable point in Overclocking is heat. Processor can only be overclocked if and only if proper cooling is there. E.g. Pentium 4 @2.0 GHz Processor can be overclocked to gain 2.2 GHz Clock speed.

Is it Risky?

Addressing Modes

Addressing modes are the way to identify operands in machine language instructions. It defines how to calculate effective address of operand with the information held in registers and/or constants contained by a machine instruction.
Some commonly used addressing modes are as follows:

Implied Mode: In this addressing mode operands are specified implicitly in the definition of instruction. E.g. complement Accumulator. In this instruction operand in the accumulator is implicitly defined in the instruction.
Example: CLA

Immediate Mode: In this addressing mode operand is specified in the instruction itself. Hence instruction contains operand instead of Address field. These addressing modes are used for the initialization of registers to a constant value.
Example: MOV R2, 123

Scanning Technologies

Four types of scanning techniques are used by manufactures to generate soft copy of color images or documents:
1) Multi Pass Technology
2) Single Pass Technology
3) Photo Multiplier Tubes(PMT) Technology
4) Contact I Image sensing Technology.

Multi Pass Technology:This scanning system was used in traditional scanners. Three different light sources (i.e. Red, Green and Blue) are used to scan the image. First red light is switched on and green and blue are left off. Scanning is done with red light source. In second pass red and blue are left off and image is scanned with green light source. In third pass image is scanned with blue light by placing red and green sources in off condition. Result obtained from these three scans is combined to get the final image scan.This problem has the problem that all the scans must be precisely aligned so that when images are combined image with sharp edges can be generated.

Flash Memory

It is a type of EEPROM that is much faster than traditional EEPROM. It reads or writes data in form of blocks. Block size is usually 512 bytes.

Sometimes flash memory is termed as flash RAM. But there is a much difference between flash RAM and flash memory. Flash RAM requires constant power to maintain its contents whereas flash ROM can store its contents even without any power.

Inside Flash Chips

Boot Block Section: - This area is used for booting and may consist of one or more blocks that is kept secure from erasing blocks. This block is generally used to store firmware of for memory management.

Block Erase Section: -It is the user working area and is divided into blocks. This area can be accessed randomly for read/write operations. Memory Erased blocks contain no data.

Types of Flash Memories

Display Problem Solutions

Computer is nothing if it is not generating display because user can’t work on that. This Problem can arise due to any of the following reason:
a) Due to Monitor Problem
b) Due to Motherboard/RAM Problem
c) Due to loose Connections
d) Due to wrong CMOS settings
e) Due to Wrong Display Settings
f) SMPS faulty

Here are some troubleshooting steps that can be used to resolve display problems.

Case1: If Monitor is Faulty
Symptoms: Faded Colors, Red Display, Green Display, Blue Display, distorted display, lines on monitor, display too bright or too fade.
Solution: This problem can be due to any of the following reasons
1) Display connection is loose, Tight them Properly
2) Data Cable is Faulty, Change that.
3) PCB is dry soldiered, Re Soldier the PCB, especially neck card.
4) Neck card IC can be faulty, Change that.
5) FBT Faulty, Change that with same value

90% of such problems can be solved just be re soldiering the neck card and changing display cable. 

Case2: if Motherboard /RAM are faulty

Direct Memory Access (DMA)

Data transfer between I/O devices and memory is slow due to the speed mismatch in their speeds. This is avoided by removing the CPU from the path and letting the peripheral device manage the memory buses directly. This   “data transfer between I/O device and memory without the involvement of CPU is called Direct Memory Access or DMA”.  

In this type of data transfer CPU remains free for another processes and has no control of the memory buses.  In DMA CPU make use of two control signals i.e. Bus Request (BR) and Bus Grant (BG). BR signal is used by the DMA controller to request the CPU for the control of buses. When this signal is active, CPU terminate the current execution of instruction and places  data bus, address bus, and read and write lines into high impedance state. This high impedance state works like open circuit and output is disconnected.BG Signal is used by the CPU to inform that all buses are now in high impedance state and the DMA controller can take the control of buses.

When this transfer is over the DMA disables the Bus Request Signal and CPU Disables the Bus Grant Signal and takes back the control of buses and returns back to its normal Operation.

Two Types of DMA Transfer:-When the buses are under the control of DMA data transfer can be in following ways

How Laser Printers Work

Laser printers ware invented at XEROX in 1969 by by researcher Gary Starkweather.Laser Printers are digital printing devices that are used to create high quality text and graphics on plain printer.

Working Principle
1)A laser beam projects an image of the page to be printed onto an electrically charged rotating Photo sensitive drum coated with selenium.
2) Photo conductivity allows charge to leak away from the areas which are exposed to light and the area gets positively charged.
3)Toner particles are then electrostatically picked up by the drum’s charged areas, which have  been exposed to light.
4)The drum then prints the image onto paper by direct contact and heat, which fuses the ink to the paper.

RAID (Redundant Array of independent disks)

RAID (Redundant Array of independent disks) or Redundant Array of Inexpensive Disks is a storage technology that combines multiple disk drive components into a logical unit.The main purpose of RAID is fault tolerance and get better performance.This Technique is generally used in servers where huge and important data is saved.
RAID uses number of standard schemes which are referred as levels.These levels and their associated data formats are standardized by the Storage Networking Industry Association (SNIA) in the Common RAID Disk Drive Format (DDF) standard.


RAID0(Disk Stripping)

in RAID 0 data is split  into blocks that get written across all the drives in the array.e.g instead of writing a 500MB file to one disk ,it simultaneously  write 125MB to each of four different disks(if disks are five than 100MB each), offering superior I/O performance but no

Difference Between RISC and CISC

No.	RISC	CISC
1	It is an acronym for Reduced Instruction Set Computer. It is a type of microprocessor that has been designed to carry out few instructions at the same time.	CISC stands for Complex Instruction Set Computer. It is actually a CPU which is capable of executing many operations through a single instruction.
2	Faster than CISC	Slower than RISC chips when performing instructions
3	Pipelining can be implemented easily	Pipelining implementation is not easy
4	Direct addition is not possible	Direct addition between data in two memory locations. Ex.8085
5	Simple, single-cycle instructions that perform only basic Functions. Assembler instructions correspond to microcode instructions on CISC machine	A large and varied instruction set that includes simple, fast instructions for performing basic tasks, as well as complex, multi cycle Instructions that correspond to statements in an HLL.
6	RISC architecture is not widely used	At least 75% of the processor use CISC architecture
7	RISC chips require fewer transistors and cheaper to produce. Finally, it’s easier to write powerful optimized compilers	In common CISC chips are relatively slow (compared to RISC chips) per instruction, but use little (less than RISC) instructions.
8	RISC puts a greater burden on the software. Software developers need to write more lines for the same tasks	In CISC, software developers no need to write more lines for the same tasks