Previous Page | Next Page

  1. Introduction
  2. Network Model
  3. Topology
  4. Physical Media
  5. Wireless Media
  6. Network Card
  7. Modems
  8. Outside Connections
  9. Wide Area Network Connections
  10. Repeaters, Bridges, Routers
  11. Network Types
  12. Ethernet
  13. Token Ring
  14. ARCnet
  15. AppleTalk
  16. FDDI
  17. Architecture Comparisons
  18. Categories
  19. TCP/IP
  20. IPX/SPX
  21. NetBEUI
  22. AppleTalk
  23. SNA
  24. Others
  25. Suites and Network Layers
  26. Installing Drivers
  27. DNS
  28. Network Operating Systems
  29. Applications, mail, groupware, DBMS
  30. Backing up the network
  31. Troubleshooting
  32. Web, SNMP, admin, firewalls
  33. Networking Terms and Definitions
  34. Credits

Network Card Operations

Computer Bus and NIC Functionality

The NIC must have a transceiver of the correct type to transmit on its intended hardware media. Therefore when moving a NIC from one type network such as 10 Base2 and 10BaseT to the other, the adapter must be configured to use the correct transceiver (there are two connectors to support both types of network). The NIC has a permanent media access control (MAC) address which is used in order to tell what card data is for. The NIC converts between the parallel data format of the computer's internal data bus and the serial data stream on the network.

The card slots are used to put additional cards such as video cards, sound cards, internal modems, or network cards into. Some motherboards today include video and sound without the addition of a extra card. These cards slots today are mostly PCI type card slots. When talking about cards that are plugged into a PC you are talking about the expansion bus. The expansion bus is a means of a microprocessor extending its communication ability further into the outside world. It is a data exchange means between add on cards and the microprocessor and the motherboard. These busses commonly support 16 or 32 bit parallel communications as noted below. The larger the parallel bus, normally the faster the interface will be. There have been several types of expansion buses.

  • ISA - Industry Standard Architecture. Used when the original 8088 8bit microprocessor based personal computers were produced. (16 bit).
  • EISA - Extended ISA used when the 80286 thorough 80486 series microprocessors were being produced. It is backward compatible with ISA. This bus is still used but is being phased out and is almost gone today. Established in 1988. (32 bits)
  • MCI - Microchannel architecture by IBM and used mainly on IBM brand computers. Established in 1988. (16 or 32 bits).
  • PCI - Peripheral Component Interconnect. The popular expansion bus of choice. It is significantly faster than EISA. This is a 32bit bus with plug and play capability from Intel.
  • AGP - Accelerated Graphics Port. This bus is developed for fast video cards. It is currently up to 4X mode speed.

The current popular expansion bus is the PCI (Peripheral Component Interconnect) bus for all cards except the graphics cards. For graphics cards, the bus of choice is AGP. Most motherboards today have one AGP slot and several PCI slots. Your expansion cards will plug into these card slots. Be sure you get cards that match the available type of slots on your motherboard. Other popular computer buses include NuBus for the Apple Macintosh, VESA local bus, and PCMCIA (PC Card).

Configuration of a PC involves configuration of a PC's resources. These resources include various mechanisms the microprocessor and/or the system will use to talk to a add on component such as a network card, video card or sound card. Each component requires resources of the following type to talk to the rest of the system.

  • IRQ- Interrupt Request
  • Bus I/O Port - Normally 0x300, 0x280, or 0x310 for network interface cards
  • Bus memory address

With the advent of the plug and play standard, these resources are automatically allocated on newer systems, but you may need to allocate these resources manually if you configure an older system. Normally these resources may be configurable using jumpers, DIP (Dual in-line Package) switches or software which will set internal memory to store specific values on the device you are configuring. In DOS, Windows 3.1, or Windows95 a program called msd.exe will determine available IRQs. On Windows NT, Under Administrative tools, use Windows NT Diagnostic Tool, or issue the command "WINMSD.EXE".

Typical IRQ Uses

IRQUse
0System Timer
1Keyboard
2Secondary IRQ controller or video
3COM2, COM4, or bus mouse
4COM1, COM3
5LPT2 or sound
6Floppy
7Parallel Port
8Real time clock
9Unassigned, Redirected IRQ2*, sound card, third IRQ controller
10Primary SCSI controller
11Secondary SCSI controller
12PS/2 Mouse
13Math Coprocessor
14Primary Hard Drive Controller
15Secondary Hard Drive Controller

I/O Ports

I/O Ports serve as the address that the microprocessor uses when communication with the device

PortUse
200Game Port
210
220
230Bus Mouse
240
250
260
270LPT3
280
290
2a0
2b0
2c0
2d0
2e0
2f0COM2
300Network Interface card
310Network Interface card
320Hard disk controller
330
340
350
360
370LPT2
380
390
3a0
3b0LPT1
3c0EGA/VGA video adapter
3d0CGA(Obsolete) video adapter
3e0
3f0floppy disk controller
3f8COM1

Network cards typically use port hexadecimal addresses 280, 300, 320, or 360.

Memory buffer

Some cards such as the network interface card will require a buffer memory area due to the speed and quantity of information that must be transferred between the card and the rest of the system. These addresses are normally unique for each card. Network interface cards typically use D8000 for their base memory address.

Other card enhancements to improve throughput to/from the card

  • Direct Memory Access (DMA) - A controller that can transfer information between system memory and the card. This relieves the microprocessor of performing this activity thus speeding up operation of the computer.
  • Bus mastering - The card moves data into system memory by taking control of the computer system data bus. The microprocessor does not need to be involved. This is similar to DMA.
  • Shared memory - Memory that is on the card that the computer system can see the same as system memory. Both the microprocessor and the card can read and write information from and to this memory.
  • RAM buffering - This involves a high speed RAM (Random Access Memory) buffer on the card where data from the computer system can be stored while waiting for transmission on the network.
  • Onboard microprocessor - The card may include its own microprocessor handling card operations and data transfer. The computer system does not need to process data from the network since it may be done on the card.

Card Drivers

Most operating systems today use drivers that work with the operating system to interface with the various cards that are installed. Usually when a card in installed on a system, a driver program must also be installed to enable the computer to use the card.