Search results
Results from the WOW.Com Content Network
Unix, Linux, OS/2, Windows NT are considered modern OS's as they switch the CPU into protected mode at startup, never return to real mode and provide all of the benefits of protected mode all of the time. 64-bit operating systems use real mode only at startup stage, and the OS kernel will switch the CPU into long mode. [2]
Some earlier computer systems, upon receiving a boot signal from a human operator or a peripheral device, may load a very small number of fixed instructions into memory at a specific location, initialize at least one CPU, and then point the CPU to the instructions and start their execution.
The startup function startup_32() for the kernel (also called the swapper or process 0) establishes memory management (paging tables and memory paging), detects the type of CPU and any additional functionality such as floating point capabilities, and then switches to non-architecture specific Linux kernel functionality via a call to start ...
The CPU uses the values of CS and IP registers to find the location of the next instruction to execute. Location of next instruction is calculated using this simple equation: Location of next instruction = (CS<<4) + (IP) This implies that after the hardware reset, the CPU will start execution at the physical address 0xFFFF0.
Researchers Anibal Sacco [75] and Alfredo Ortega, from Core Security Technologies, demonstrated how to insert malicious code into the decompression routines in the BIOS, allowing for nearly full control of the PC at start-up, even before the operating system is booted. The proof-of-concept does not exploit a flaw in the BIOS implementation, but ...
The BIOS begins its POST when the CPU is reset. The first memory location the CPU tries to execute is known as the reset vector. In the case of a hard reboot, the northbridge will direct a code fetch request to the BIOS located on the system flash memory.
When a CPU wishes to send an interrupt to another CPU, it stores the interrupt vector and the identifier of the target's local APIC in the Interrupt Command Register (ICR) of its own local APIC. A message is then sent via the APIC bus to the target's local APIC, which then issues a corresponding interrupt to its own CPU.
The instruction cycle (also known as the fetch–decode–execute cycle, or simply the fetch–execute cycle) is the cycle that the central processing unit (CPU) follows from boot-up until the computer has shut down in order to process instructions. It is composed of three main stages: the fetch stage, the decode stage, and the execute stage.