Draft Document for Review April 7, 2004 6:15 pm

6947ch02.fm

z990

Image

Mode

Modes

Operating

Systems

z/OS

Linux on zSeries

Addressing

Modes

64-bit

Architecture

ESA/390 Mode

CPs

z/VM OS/390 R10

Operating System

Option

Mode

CPs and zAAPs

(z/OS 1.6 and above only)

z/VSE

31-bit

Architecture

VSE/ESA

Mode

Linux for S/390

 

 

 

ESA/390 TPF Mode TPF

CPs only

Logically

 

 

Partitioned

Coupling Facility Mode

CFCC

Mode

ICFs and/or CPs

 

Linux on zSeries

Linux Only Mode

IFLs or CPs

z/VM

 

Linux for S/390

31-bit

Architecture

Mode

64-bit

Architecture

Mode

64-bit

Architecture Mode

Operating System

Option

31-bit

Architecture

Mode

Figure 2-15 z990 Modes of Operation diagram

Logical Partitioning overview

Logical Partitioning is a function implemented by the Processor Resource/Systems Manager (PR/SM), available on all z990 servers.

The z990 only runs in LPAR mode. This means that virtually all system aspects are now controlled by PR/SM functions.

PR/SM is very much aware of the book structure introduced on the z990. However, logical partitions do not have this awareness. Logical partitions have resources allocated to them coming from a variety of physical resources, and have no control over these physical resources from a systems standpoint—but the PR/SM functions do have.

PR/SM manages and optimizes allocation and dispatching work on the physical topology. Most physical topology knowledge that was previously handled to the operating systems is now the responsibility of PR/SM.

PR/SM always attempts to allocate all real storage for a logical partition within one book, and attempts to dispatch a logical PU on a physical PU in a book that also has the central storage for that logical partition. If not possible, a PU in an adjacent book is chosen. In general, PR/SM tries to minimize the number of books required to allocate the resources of a given logical partition. In addition, PR/SM always tries to re-dispatch a logical PU on the same physical PU to assure that as much as possible of the L1 cache content can be reused.

Chapter 2. System structure and design 57

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Page 71
Image 71
IBM 990 manual Logical Partitioning overview, Vse/Esa
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990 specifications

The IBM 990 series, often referred to in the context of IBM's pioneering efforts in the realm of mainframe computing, represents a unique chapter in the history of information technology. Introduced in the late 1960s, the IBM 990 series was designed as a powerful tool for enterprise-level data processing and scientific calculations, showcasing the company's commitment to advancing computing capabilities.

One of the main features of the IBM 990 was its architecture, which was built to support a wide range of applications, from business processing to complex scientific computations. The system employed a 32-bit word length, which was advanced for its time, allowing for more flexible and efficient data handling. CPUs in the IBM 990 series supported multiple instructions per cycle, which contributed significantly to the overall efficiency and processing power of the machines.

The technology behind the IBM 990 was also notable for its use of solid-state technology. This provided a shift away from vacuum tube systems that were prevalent in earlier computing systems, enhancing the reliability and longevity of the hardware. The IBM 990 series utilized core memory, which was faster and more reliable than the magnetic drum memory systems that had been standard up to that point.

Another defining characteristic of the IBM 990 was its extensibility. Organizations could configure the machine to suit their specific needs by adding memory, storage, and peripheral devices as required. This modular approach facilitated the growth of systems alongside the technological and operational demands of the business environments they served.

In terms of software, the IBM 990 series was compatible with a variety of operating systems and programming environments, including FORTRAN and COBOL, enabling users to access a broader array of applications. This versatility was a significant advantage, making the IBM 990 an appealing choice for educational institutions, research facilities, and enterprises alike.

Moreover, the IBM 990 was engineered to support multiprocessing, which allowed multiple processes to run simultaneously, further increasing its effectiveness in tackling complex computing tasks.

In summary, the IBM 990 series represents a significant advancement in computing technology during the late 20th century. With a robust architecture, versatile configuration options, and a focus on solid-state technology, the IBM 990 facilitated substantial improvements in data processing capabilities, making it a cornerstone for many businesses and academic institutions of its time. Its impact can still be seen today in the continued evolution of mainframe computing.
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