Video summary 4

BIOS and System Resources BIOS is Firmware and the very first program initiated during the boot process of a PC. BIOS is a set of instructions written as ROM which is "Read Only Memory"; this means that it is permanent and cannot be edited although it can be changed by flashing or by installing an entirely new motherboard; in my opining that should be referred to as replacing, as I feel that term is more accurate when a new motherboard is required to change the BIOS: Bios also does not need a power supply to maintain. BIOS initiates POST which is "Power-On Self Test": POST checks basic systems, hardware, memory and assigns system resources; BIOS also checks CMOS settings. When comparing to POST which is RAM and therefore not permanent; it can be changed by the user: With CMOS being RAM and BIOS being ROM allowing CMOS editable. Although CMOS is RAM it is able to sustain memory and survive computer shutdown while RAM is normally lost during power failure; this is because CMOS uses a coin battery to maintain its configuration, so be on the look out of a dying batter. To change the permanent instructions by replacing them, the BIOS uses a technology known as EEPROM "Electronically Erasable Programmable" ROM. Moving onto the topic of System Resources, there are four; the four resources are IRQ, I/O and Memory addresses, and DMA. IRQ "Interrupt Request" communication channel from Hardware devices to CPU; each device has its own address. Most common conflicts are; IRQ 3-com 2, com 4; IRQ 4-com 1, com 3; IRQ 5-LPT2 or sound card, and IRQ7-LPT1 (printer). I/O has addresses are similar to the device name. Memory Address is used to communicate with the CPU, and lastly DMA "Direct Memory Access", which is a direct communication channel between a device and the system menu. DMA does not require a CPU, which reduces response time; yet not all devices use DMA, but a couple of devices that use DMA are sound cards and joysticks.