Q.1. Explain the different types of Memory Modules.

Ans.: There are two types of memory modules :

(i) SIMM : Single Inline Memory Modules
(ii) DIMM : Double Inline Memory Modules

These are small printed circuit cards (PCC) on which several DRAMS memory chips are placed. Such cards are plugged into the system board of the computer. The SIMM Circuit cards contain several memory chips with contacts placed on only one edge of this PCC whereas in DIMM, it‟s on both sides of the PCC.

Q.2. Explain about the System Clock.

Ans.: Every computer has got a system clock. It‟s located in the microprocessor. The clock is design by a piece of quartz crystal. The system clock keeps the computer system coordinated. It‟s an electronic system which keeps oscillating at specified times intervals, between 0 & 1. The speed at which this oscillation takes place is called the cycle of the clock. The time taken to reach from „0‟ to „1‟ and back is called clock cycle the speed of the system clock is measured in terms of Hz.

Q.3. Explain about the System Bus.

Ans.: Bus means the electronic path between various components Bus refers to particular types of a cable. Each cable of a bus carries information of one bit. Buses are of 3 types :
(1) Address Bus

(2) Data Bus
(3) Control Bus

(1) Address Bus : It carries the address of memory location of required instructions and data. The address Bus is unidirectional, i.e., data flows in one direction from CPU to memory. The address bus data determines the maximum number of memory addresses. This capacity is measured in binary form. E.g. A 2 –bit address bus will provide 22 addresses.

(2) Data Bus : Data bus is an electronic path that connects CPU, memory & other h/w devices. Data bus carries the data from CPU to memory or I/P–O/P devices and vice versa. It‟s a directional bus because it can transmit data in either direction. The processing speed of a computer increases if the data bus is large as it takes more data at one time.

(3) Control Bus : Control Bus controls the memory and I/O devices. This bus is bidirectional. 
The CPU sends signals on the control bus to enable the O/P of the addressed memory devices.

Data Bus Standard : Bus standard represents the architecture of a bus. Following are important data bus standards :

(i) Industry Standard Architecture (ISA) : This bus standard was the first standard released by IBM. It has 24 address lines & 16 data lines. It can be used only in a single user system. ISA bus is a low cost bus. It has a low data transfer rate. It could not take the full advantage of the 32-bit micro processor.

(ii) Micro Channel Architecture (MCA) : IBM developed MCA bus standard. With this, bus speed was elevated from 8.33 MHz to 10MHz which was further increased to 20 MHz & bandwidth increased from 16 bits to 32 bits.

(iii) Enhanced Industry Standard Architecture (EISA) : These buses are of 32 bit & helpful in multiprogramming. Due to low data transfer speed, ISA cannot be used for multi tasking & multi-user-systems. EISA is appropriate for multi user systems. The data transfer rate of EISA is double of that of ISA. The size of EISA is same as that of ISA, so both EISA & ISA cards can be fixed in EISA connector slot. EISA connectors are quite expenses.

(iv) Peripheral Component Interconnect (PCI) : This bus standard was developed by Intel. It‟s a 64 bit bus & works on 66 MHz. Earlier, a 32 bit PCI bus was developed having a speed of 33 MHz. PCI bus has greater

speed and has 4 interrupt channels. It also has a PCI bridge through which the bus can be connected to various other devices.

Q.4 Explain the role of Expansion Slots.

Ans.: The main function of the mother board is to enable connectivity between various parts of a computer with processor & memory. Various hardware cards can be fixed on the mother board to save different purposes. Mother boards have slots to fix the various cards-like video card, modem, sound cards etc, expansion slots on the motherboard can be used fro the following purposes:
(i) To connect the internal devices of a computer eg. Hard disk etc. to the computer bus.
(ii) To connect the computer to the external devices like mouse, printer etc.
The above functions are carried out with the help of adapters.

Q.5. List out various Cards and elaborate about them?

Ans.: (1) Sound Card : This card is used for I/P& O/P sound. Microphone is used to I/P& speaker is used to O/P the sound. The sound card converts the sound into computer language & vice versa. All sound cards are based on MIDI (Musical Instrument Digital Interface) which represents the music in electronic form. The main part of sound card is DSP (Digital signal processor) which uses arithmetic logic to bring out sound effects. Sound card comes with 16-bit computers. DAC (Digital to Analog) and ADC (Analog to Digital) sound card uses DMA (Direct memory Access) channel is to read & write the digital audio data.

(2) SCSI (Small Compute System Interface) : This technology is used in high speed hard disk. It‟s often used in servers where high volume of data is used. At present different versions of SCSI are used. The capacity of the SCSI is determined by the bus width and speed of the interface. Through SCSI the computers bus is extended by means of the cable. It‟s an extension of the computer bus.

(3) Network Cards : N/W card is a versatile device because it performs a number of tasks that contribute to the entire process of transmitting and receiving data between computers. It links a computer to another computer of the n/w through cable wires. A seven-layer model of OSI (Open System Interface) is used in the Internet for receiving and transmitting of data. The information passes through there seven layers. N/W card implements the physical layer and half of the data link layer.

Q.6. Describe briefly about different types of Ports.

Ans.: Computers have an interface called ports. Peripheral devices are interfaced to the computers through these ports. Data flows in & out through these ports. Ports are of 2 types, Parallel & Serial.

A parallel port allows the transfer of all the bits of a word simultaneously. In parallel interface there are multiple lines to connect the peripherals to the port. A parallel interface is used to transfer data at a faster rate for higher speed peripherals such as disk and tapes.

A Serial port allows serial data transfer. In serial data transfer, one bit of data is transmitted at a time. In serial interface, only one line or a pair of line is used to transmit data. It‟s used for slow speed peripherals such as terminal. Printers employ either serial interface or parallel interface. The disadvantage of a serial/ parallel port is that only one device can be connected to a port.

Q.7. Explain about RS 232 C.

Ans.: The RS 232 C is a standard for serial data transfer. It specifies standard for 25 signals & hand shake signals which are used between DCE & DTE. The voltage levels, maximum capacitance for there signal lines are also described in this standard. The standard RS-232 C interface is usually provided in computers for serial data transfer. A voltage between -3 V & -15 V under load is used for high logic or mark. A voltage between +3 V & +15 V under load is used for low logic or space. The voltage levels are not TTL compatible.

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