CPU modes

CPU modes (also called processor modes, CPU states, CPU privilege levels and other names) are operating modes for the central processing unit of some computer architectures that place restrictions on the type and scope of operations that can be performed by certain processes being run by the CPU. This design allows the operating system to run with more privileges than application software.

Ideally, only highly trusted kernel code is allowed to execute in the unrestricted mode; everything else (including non-supervisory portions of the operating system) runs in a restricted mode and must use a system call to request the kernel perform on its behalf any operation that could damage or compromise the system, making it impossible for untrusted programs to alter or damage other programs (or the computing system itself).

In practice, however, system calls take time and can hurt the performance of a computing system, so it is not uncommon for system designers to allow some time-critical software (especially device drivers) to run with full kernel privileges.

Mode

Mode (Latin: modus meaning "manner, tune, measure, due measure, rhythm, melody") may refer to:

Language

Music

Modes (Unix)

Modes are the file system permissions given to "user", "group" and "others" classes to access files.

Modes are shown when listing files in long format, or, if Access Control Lists are in use, using getfacl.

Modes can be changed with chmod (for traditional Unix permissions) or with setfacl (for Access Control Lists).

For traditional Unix permissions, the symbolic mode is composed of three components, which are combined to form a single string of text:

The references (or classes) are used to distinguish the users to whom the permissions apply. If no references are specified it defaults to "all". They are represented by one or more of the following letters:

The chmod program uses an operator to specify how the modes of a file should be adjusted. The following operators are accepted:

The modes indicate which permissions are to be granted or taken away from the specified classes. There are three basic modes which correspond to the basic permissions:

The combination of these three components produces a string that is understood by the chmod command. Multiple changes can be specified by separating multiple symbolic modes with commas.

Mode (music)

In the theory of Western music, mode (from Latin modus, "measure, standard, manner, way, size, limit of quantity, method") (Powers 2001, Introduction; OED) generally refers to a type of scale, coupled with a set of characteristic melodic behaviours. This use, still the most common in recent years, reflects a tradition dating to the Middle Ages, itself inspired by the theory of ancient Greek music.

Mode as a general concept

Regarding the concept of mode as applied to pitch relationships generally, Harold S. Powers proposed mode as a general term but limited for melody types, which were based on the modal interpretation of ancient Greek octave species called tonos (τόνος) or harmonia (ἁρμονία), with "most of the area between ... being in the domain of mode" (Powers 2001, §I,3). This synthesis between tonus as a church tone and the older meaning associated with an octave species was done by medieval theorists for the Western monodic plainchant tradition (see Hucbald and Aurelian). It is generally assumed that Carolingian theorists imported monastic Octoechos propagated in the patriarchates of Jerusalem (Mar Saba) and Constantinople (Stoudios Monastery) which meant the eight echoi they used for the composition of hymns (e.g., Wellesz 1954, 41 ff.), though direct adaptations of Byzantine chants in the survived Gregorian repertoire are extremely rare.

Central processing unit

A central processing unit (CPU) is the electronic circuitry within a computer that carries out the instructions of a computer program by performing the basic arithmetic, logical, control and input/output (I/O) operations specified by the instructions. The term has been used in the computer industry at least since the early 1960s. Traditionally, the term "CPU" refers to a processor, more specifically to its processing unit and control unit (CU), distinguishing these core elements of a computer from external components such as main memory and I/O circuitry.

The form, design and implementation of CPUs have changed over the course of their history, but their fundamental operation remains almost unchanged. Principal components of a CPU include the arithmetic logic unit (ALU) that performs arithmetic and logic operations, processor registers that supply operands to the ALU and store the results of ALU operations, and a control unit that fetches instructions from memory and "executes" them by directing the coordinated operations of the ALU, registers and other components.

Freescale 683XX

The Freescale 683xx (formerly Motorola 683xx) is a family of compatible microcontrollers that use a Freescale 68000-based CPU core. The family was designed using a hardware description language, making the parts synthesizable, and amenable to improved fabrication processes, such as die shrinks.

There are two CPU cores used in the 683xx family: the 68EC000 and the CPU32. The instruction set of the CPU32 core is similar to the 68020 without bitfield instructions, and with a few instructions unique to the CPU32 core, such as table lookup and interpolate instructions, and a low-power stop mode.

The modules of the microcontroller were designed independently and released as new CPUs could be tested. This process let the architects perform "design-ahead" so that when silicon technologies were available, Motorola had designs ready to implement and go to market. Many of these submodules have been carried forward into the Coldfire line of processors.

The microcontrollers consist of a series of modules, connected by an internal bus:

Rodney (New Glasgow) Airport

Rodney (New Glasgow) Airport, (TC LID: CPU3), is located 4 nautical miles (7.4 km; 4.6 mi) southeast of Rodney, Ontario, Canada.

References