some memory locations can only be modified by the kernel itself. You can call it a kind of a lock. So kernel mode basically is the "power" to modify those memory locations. when people say kernel mode is not available on fw 1.5x and above, it means you dont have the power to change the values of those memory locations.
A processor privilege level where the processor is capable of accessing resources directly.
Kernel mode is the CPU mode that the UNIX kernel runs in. In this mode, the CPU has unrestricted access to all system resources (including disks, memory, etc.). The CPU usually enters kernel mode during system calls and during the normal timeslicing operations of the UNIX operating system.
The most privileged processor access mode. The operating system's most privileged services, such as I/O drivers and the pager, run in kernel mode. When in kernel mode, the processor has complete control of, and responsibility for, the system.
A highly privileged mode of operation where program code has direct access to all memory, including the address spaces of all user-mode processes and applications, and to hardware. Kernel mode is also known as supervisor mode, protected mode, or Ring 0.
The privileged mode of the operating system where the kernel runs. This mode gives the kernel complete access to the computer.
The state in which a process runs kernel code. Contrast with user mode.