* BIOS: The first program activated during boot. * BIOS is asset of instructions written as ROM on a chip on the motherboard * It is permanent , cannot be edited , and does not require power to maintain content * Startup BIOS activates the bootstrap loader which runs the POST or Power On Self-Test * Which checks memory and assigns system resources * CMOS also checked by startup BIOS and compares to hardware found during POST * CMOS settings are stored in RAM and are not permanent and may be changed by the user * BIOS and CMOS are used interchangeably by term but are different * BIOS is stored in ROM and is permanent and cannot be edited * CMOS is stored in RAM is volatile and can be edited * Both stored in different chips * CMOS battery saves settings for configurations during power outages * If the battery starts to die the computers system clock will start to lose time * If the battery is dead you will get a checksum error during boot * You can still boot simply clear the checksum error And let the startup BIOS use the default CMOS setting stored in the BIOS which is ROM and not disturbed by power outages * Flashing the BIOS * BIOS cannot be edited but can be change by replacing the motherboard or Flashing the BIOS * BIOS is firmware not hardware or software * BIOS uses EEPROM or Electronically Erasable Programmable ROM * Old instructions are replaced with new ones * The BIOS is very important to the startup of the computer. These instruction are permanently written and are always there as a default. Once the startup BIOS is activated and the POST start the computer does a lot of self-test and checks that the user never realizes is happening. And as the CMOS is included in these series of checks the BIOS is looking for any hardware as well. System Resources ; which are (4) * IRQ * I/O ADDRESSES * MEMORY ADDRESSES * DMA * IRQ or Interrupt request; it’s the communication channel from hardware devices to CPU * Each device is assigned its own IRQ channel * When a device wants to communicate to the CPU the CPU knows which device is communicating because it knows which IRQ signal was sent * IRQ * IRQ3 – comport 2 , comport 4 * IRQ4 – comport 1 , comport 3 * IRQ5 – LPT 2 or sound card * IRQ7 – LPT 1 (printer) * I/O Address * Input Output addresses ; each device is assigned its own I/O address * When the CPU needs to send instructions to addresses it uses the I/O address to communicate * All devices listen and respond to their own I/O address * I/O address is similar to the devices name * Example : the CPU calls out the hard drives name to let it know it has instructions for it * Each hardware device is assigned its own memory address which it uses to communicate with the CPU , this is where information and instructions are stored and where work gets done * DMA –Direct Memory Access * Transfers info directly between devices and does not have to go through the CPU this allows faster access time , but not all devices uses DMA * Sound cards and joystick use DMA the reduces response time * IRQ communicates ;device to CPU * Memory Addresses ; instructions and work stored here * DMA ; device to memory * You can see System Resources Assignments in System Information or Device Manager * Use Device Manager to troubleshoot hardware and resolve resource conflicts
The System Resources make up the communicating and working functions of the computer. The IRQ has the devices like in military format waiting for and giving instructions to the CPU, but having to wait to speak until instructed to. The DMA helps the device gain faster access time by bypassing the CPU. The input/output address is most important in storing instruction and processing work for further work.