General Purpose Computers

A general-purpose computer is termed as the one which is enough able to perform all of computing tasks in some given time period and with the help of most appropriate application. Some of the common examples of general-purpose computers are tablets, notebooks, and desktops etc (Hennessy and Patterson, 2011)

1.1. Architecture

A general-purpose computer system is made up of both of the software and hardware. The processor is termed as the heart of computer. Hardware is responsible for the execution of programs. There is memory in computer too, and there are various types of it. For the storage of programs, memory is utilized while in order to make them run processor is required, along with it, it also stores the data which are being manipulated by the program. Computer does have some devices in order to store or exchange with the world outside of them. In this case, input is made with the help of keyboard; output is displayed on the monitor screen; for exchanging processes, data and programs are moved from disk drive or towards disk drive. There are different kinds of registers in the CPU. General purpose registers are utilized for the general use. Unless there is another implication of context, register will deal with the General Purpose Register in the CPU. Now-a-days modern computers do have 16 and 64 registers. There are different types of registers including: the stack pointer (SP), the Condition Code (Flags/Status) register, the ALU Input and Output registers, the Instruction Register (IR), the Program Counter Register (PC) (Jones et al, 2011). 

The overall functionality and operation of the computers are controlled with the help of software. There are different “software layers” in the computer. Generally, a layer interacts immediately with the layer which is above or below it (Tsai and Hung, 2012).

Software layers

Source: (Mueller, S.M. and Paul, 2013)

2. Memory organization

2.1. Main Memory (RAM) Organization

There are different kinds of memory in computers (semi-conductor, DVDs, magnetic disks, USB sticks etc) for holding programs and data. Every type owns its own features and usages. Basically there are three kinds of memory in the model of general purpose computer:

  • Register memory
  • Main memory
  • Disk memory (Mueller and Paul, 2013)

If all of the register bits are summed up in the CPU, then the total memory of CPU may not exceed 5000 bits. Most of the computational tasks which are being done by computer do require a lot of memory. Main memory is also a fast memory and it is also large in size. Typical sizes of main memory for different computers are: database server 8GB, fileserver 4GB, and PC 512MB. The most common type of main memory is RAM (Random Access Memory). RAM is present on the motherboard and its size is 12 inches less than the CPU. ROM is quite identical to ROM, except for that, its contents are not lost even in case of turning off computer and overwriting cannot be done in ROM. ROM is termed as non-volatile. Main memory is comparatively slower than register memory. RAM is used for the storage of data (numbers, strings) and instructions. The loading of program is done into RAM from disk to be executed by CPU. With the help of an addressing scheme, identification of positions in RAM is done. RAM is also volatile like registers (Schlomer et al, 2010).


2.2. Register Memory

Registers are the memories which are present in the CPU Central Processing Unit. They are small in size and very less in number; typically the size of register is even less 64 bits. The read and write operations are performed easily on the contents of register. The operations are performed faster than main memory and even faster than disk memory.  The size of the registers is dependent on the register type. The size of general purpose s quite often used for defining the word size of architecture. On contrary to disk memory and main memory, the registers are referred with the help of particular instructions or through encoding of register number in the computer instruction. If CPU is turned off, then register contents are lost, therefore it is not effective to hold the long-term information in registers. However registers do have the fastest memories (Combe and Drif, 2009).

2.3. Disk Memory

Disk memory is used in order to keep data and programs. Disk is non-volatile, as its contents are not lost even in the case when the power is turned off. The range of hard disk is from 100GB to more than 1TB. As compared to main memory and registers, disks are slower. Disk drivers can do the transfer of around thousand bites. The location of disk is done with the help of particular disk addressing scheme (like sector and track numbers) (Conlan, 2009).

3. Operating system components

With turning on the computer, loading of operating system is done through booting program. However more system modules can be loaded as required, the main component is termed as kernel. Kernel is located in the memory. The standards are set up by the operating system for programs that are being run into the computer. The link of applications is with the operating systems for file management operations and user interface. Operating system is known as supervisor or executive, following are the components of operating systems (Comer, 2011).

3.1. User Interface

The user interface involves the interaction method, menus and windows between the computer and user. All of the operations are performed through commands in graphical user interface (GUIs). A command-line interface is involved in most of the operating systems. Operating system also supports some of the optional interfaces.

3.2. Job Management

Job management manages the sequence and time. Batch files can be written in order to perform different operations, scheduling of which can be done in order to start at a specified time (Bobrow, 2014).

3.3. Task Management

Multitasking involves the ability to perform different programs at one time; it is available in all of the operating systems. The priority of the application is done in the server environment and mainframe for running the programs slower or faster based on the tasks.

3.4. Data Management

Data management do have the track of data stored on the solid state storage or disks. The application program refers to the data with the help of specific location or through file name in the file. The file system of operating system knows that where the data is located and with the help of programming interface, interaction is done in between the operating system and application. Whenever any application requires the retrieval or storage of data, file system of operating system is called, which is responsible for opening, writing, reading and closing files (Schlomer et al, 2010).

3.5. Device Management

Peripheral devices are controlled by the device management through commands in the command language. The software routine which refers to ever y device is known as driver, OS needs drivers for peripherals which are linked with the computer.

3.6. Security

Operating system gives password protection for keeping unauthorized users away from system. Operating systems do the maintenance of activity logs and give accounting of time for purposes of billing. They also give recovery routines and backups for starting the event of system failure (Combe and Drif, 2009).

4. Cisco 2600 series router

Cisco 2600 series routers are termed as the access routers with having connections to LAN and WAN. The configuration of these connections can be done with the help of WAN interface cards and interchangeable module.


Source: Leva et al (2013)

5. Hardware features

Following are the hardware features of Cisco 2600 series routers:

  • DRAM Dynamic random-access memory for shared memory and main memory
  • SDRAM – Synchronous dynamic random-access memory for both shared memory and main memory
  • For the storage of configuration information there is non-volatile random-access memory
  • Flash memory is used in order to store the software image of operating system. Flash memory is also termed as Compact Flash memory card in Cisco 2691 routers. Flash memory is termed as single inline memory module (SIMM) in all of the other Cisco 2600 series router
  • EIA/TIA-232 (RJ-45) is known as console port for accessing the local system with the help of console terminal
  • EIA/TIA-232 (RJ-45) is the auxiliary port for dial backup or remote access through modem (Weldezion et al, 2009).

6. Architecture

6.1. CPU

As the main function of CPU, instructions are being executed which are coded onto the operating system and subsystems are used for performing the basic operations which are required to fulfill the operation of router, for instance, system initialization, high-level control, network module and routing functions.

6.2. LAN 0 / LAN 1

There are three of the LAN controllers on motherboard. There are three types of LAN control named as:

  • Token Ring
  • Fast Ethernet
  • Ethernet

Availability is based on the particular model of 2600 router.

6.3. AIM Socket

With the help of this socket, (AIM) Advanced Interface Module cards are accommodated. This socket consists of 100-pins internally, which permits some of functions that do not need any external links like encryption, compression and so forth. There are two AIM sockets in the model 2691 (Leva et al, 2013).

6.4. Host PCI Bridge

In between the system bus, CPU bus and PCI bus, it works as the bridge interface, where there is connection of other interfaces and Network Modules.

6.5. System Bus

This is used for the purpose of communication in between the interface boards and CPU Board. There is PCI bus on the 2600 platform.

6.6. CPU Bus

The CPU uses it for accessing different parts of the system and for the transformation of data and instruction from or to the particular address of memory.

6.7. Power Supply

The operations can be performed on 2600 series through Redundant Power Supply (RPS).

7. Memory Organization

The memory is being used in different forms for the storing the data like for storing the operating system (Cisco IOS software), packets, bootstrap, the configuration and so forth. There are four main types of memory on 2600 platforms:

  • BOOT RoM
  • Flash memory (Comer, 2011)



Source: (Schlomer et al, 2010)

7.1. Boot ROM

Boot ROM is used in order to store the startup diagnostic code permanently (ROM Monitor).

The main purpose of BOOTROM is to do the diagnostics of hardware during the router bootup, and Power on Self Test (POST), and for loading the Cisco IOS software to memory from the flash. The replacement of Boot ROM can be done, but it cannot be erased.

7.2. DRAM

For executing Cisco IOS software, routing table, packets, running configuration and Fast Switching Cache, DRAM is used.

There are two DRAM sockets in the 2600 series and it uses non-parity DRAM (Combe and Drif, 2009).

7.3. NVRAM

NVRAM is used in order to storage the permanent startup configuration. Except for 2691, it is EPROM, where the storage of startup configuration is done in the Flash memory where the loading of boot code is done.

7.4. Flash memory

Flash memory is used in order to store the software image of operating system. Flash memory is also termed as Compact Flash memory card in Cisco 2691 routers.

8. Operating system components

The main function of operating system of Cisco is to enable the communication of data in between the nodes of network. Along with it switching and routing, operating system of Cisco provides a large number of other services that can be used by administrator for improving the security and performance of network traffic. Some of these services are proxy capability, intelligent routing, Quality of service, deep packet inspection, policy enforcement, firewall capabilities, authentication and encryption. IOS can also provide support to the unified services of communication and call processing.

There are different types of operating systems for Cisco: Nexus OS, IOS XR, IOS XE (Bobrow, 2014).








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