Message Queue Service, Checkpoint Agent

NetPlane Core Services	Message Queue Service

2.5.2.2.2Checkpoint Node Director

The Checkpoint Node Director (CPND) runs as process both on payload blades and on the two system manager nodes. Its tasks are:

z Accepting checkpoint requests from Checkpoint Agents and streamline requests from applications to checkpoints

z Maintaining and controlling the state information pertaining to checkpoints

z Coordinating read and write accesses to/from checkpoint applications across the cluster

z Keeping track of CPNDs on other nodes in order to update the local data if a CPND that is managing the active checkpoint goes down

z Maintaining local replicas in shared memory

z Storing checkpoint control information in the shared memory so that it may be retrieved after a CPND restart

z Managing accesses to sister replicas and coordinating accesses from other applications to the replicas within the scope of the CPND

2.5.2.2.3Checkpoint Agent

The Checkpoint Agent (CPA) is a linkable library available to applications that want to use checkpoint services.

2.5.3Message Queue Service

The Message Queue Service (MQSv) implements the SAF Message service API.

2.5.3.1Basic Functionality

Sender application(s) which use this service, send messages to queues and queue groups managed by MQSv and not to receiving application(s) directly. This means, if a process dies, the message persists in the queue and can be read by the restarted application or by another process.

Applications may create and destroy queues, where each queue has a globally unique name. Multiple senders may then direct messages to a queue, while a single receiver may read messages from the named queue.

Applications may group several queues into a system-wide named queue group. When sending a message to a queue group, a group policy dictates which queue actually receives the message. The sender does not know how many queues are in the group or what the policy is.

2.5.3.2Architecture

The MQSv service consists of the following three subparts:

zMessage Queue Director

zMessage Queue Node Director

zMessage Queue Agent

30	NetPlane Core Services Overview User’s Guide (6806800C08B)

6806800C08B specifications

The Motorola 68000 microprocessor, particularly the revision marked as 68000C08B, stands out as a seminal component in the evolution of computing technology. Introduced in 1979, the 68000 architecture laid the groundwork for many advanced systems, influencing a multitude of platforms, from personal computers to game consoles.

The Motorola 68000C08B features a 16-bit data bus and a 24-bit address bus, allowing for a memory addressing capability of up to 16 MB. This architecture was pioneering for its time, enabling more extensive and complex software applications than its predecessors. The C08 revision particularly emphasized optimizing power consumption while maintaining performance, making it ideal for embedded systems and portable devices.

One of the 68000's key characteristics is its unique register set, which allows for a versatile range of operations. It consists of 8 general-purpose data registers and 8 address registers. The architecture supports both integer and floating-point operations, thanks to an integrated instruction set that facilitates complex mathematical computations, crucial for applications in graphics and gaming.

In terms of performance, the 68000 processor operates at clock speeds ranging from 8 MHz to 16 MHz, depending on the specific variant. The instruction set architecture (ISA) is known for its orthogonality, meaning that most instructions can be used interchangeably across different registers. This design simplicity allows for efficient coding and faster execution times, a significant advantage for developers.

Another remarkable feature of the 68000C08B is its capability for multitasking and improved context switching. Its advanced memory management, combined with support for virtual memory in later implementations, catered to the needs of operating systems and real-time applications, making it suitable for both consumer electronics and industrial machinery.

The Motorola 68000 family also supports a variety of peripherals, enhancing its flexibility as a microcontroller. This compatibility allowed manufacturers to create diverse product lines, from keypads and mice to modems and hard drives.

In summary, the Motorola 68000C08B microprocessor not only advanced the landscape of computer technology in the late 20th century but also helped set the stage for future innovations through its architecture, performance capabilities, and versatility in numerous applications. Its legacy continues to influence modern computing paradigms, ensuring the 68000 remains an essential chapter in the history of microprocessors.