webpointmorpheus Computer Info
Boards & BIOS

     Overview      Devices      POST Codes      Expansion Slots      DMA

©2005 - material compiled by Bob Carnaghi, www.webpointmorpheus.com

Overview     Top of Page

Inside a computer case (the box, or tower) the base component is the Motherboard. The Motherboard has slots for the system memory, the processor, CD-ROM, hard drive, floppy drive, keyboard, mouse, monitor, and all other input/output devices. All the devices connect to the Motherboard. This incredible maze of devices is integrated in a remarkably ordered fashion by a series of busses, controllers, chipsets, BIOS (Basic Input/Output System) and other means as necessary.

The initial and base operation of the computer as it boots into operation is controlled by a CMOS (Complimentary Metal Oxide Semiconductor) chip which holds specific information about the computer's hardware. (Hardware is defined as anything you can touch, software is defined as a program or set of instructions digitally placed on a disk.) The CMOS settings govern how the computer basically operates and is configured. The basic system device drivers are held in ROM (Read Only Memory) BIOS, which is loaded when the computer first boots.

Devices     Top of Page

How are all the devices on the computer able to commuinciate in an orderly fashion? They each make a request of the CPU using an IRQ (Interrupt Request) number. When a particular set of instructions is sent to the CPU with the IRQ, the computer knows where it comes from, and how it needs to be handled. In this fashion, the computer is able to make sense of all the attached devices and their functions.

POST Error Codes     Top of Page

POST (Power On Self Test) is the method that the computer uses at boot to check the workability of the basic hardware devices. As the computer rises into operation, each device has an inherent routine to test itself, and place an error code on the screen if necessary. Listed below are some of the more common error codes.

Expansion Slots     Top of Page

Expansion slots are the means of extending functionality of the computer. Commonly there are modems, network cards, video cards, ATA expansion cards, and many other types of PCI or other expansion cards avaliable. The list below shows the popular types of expansion slots and their capabilities. In essence, the list below is a historical progression of the modes of expansion slot capabilities.

DMA & Bus Mastering     Top of Page

DMA (Direct Memory Access) is the method where the CPU is relieved of certain data transfer functions by allowing peripherals to directly access the system memory. In a system with DMA there are typically two 8237 chips with 7 DMA channels to move data directly to the memory addresses. Due to certain inherent limitations, the practice of DMA has grown into what is now known as Bus Mastering. Bus Mastering is also known as Ultra DMA, and most EIDE devices are capable of Bus Mastering. Bus Mastering enables a device to bypass the 8237 DMA controller chip and access the address bus when it is open. The process uses the address bus when it is open, senses when there is data moving to/from the CPU, and intellegently adjusts its data transfer accordingly to increase speed and efficiency.