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

6947ch08.fm

IBM utilizes the Large Systems Performance Reference (LSPR) method to provide relative capacity information, which takes into account processor design sensitivities to workload type.

LSPR benchmarks are laboratory controlled tests of representative workload environments, objectively measured and analyzed.

8.8.1 Large Systems Performance Reference (LSPR)

IBM’s Large Systems Performance Reference (LSPR) method is intended to provide comprehensive S/370™, S/390 and zSeries arch itecture processor capacity data across a wide variety of operating systems, or System Control Programs (SCPs), and workload environments.

To assure that the processor is the LSPR’s primary focus, the processor capacity data reported assume sufficient external resources, such as storage size, or number of channels, control units and I/O devices, so as to prevent any significant external resource constraints.

LSPR data is based on a set of measured benchmarks and analysis, and is intended to be used to estimate the capacity expectation for a given production workload when considering a move to a new processor.

The average rate that a processors execute instructions is quoted as Millions of Instructions Per Second (MIPS). With today’s high-performance processors, the actual MIPS rate achieved is extremely sensitive to the workload type being run, and its relationship to underlying processor design. Therefore, the relative capacity of one processor to other will be very dependent on the type of the work being run.

For this reason, IBM has chosen to provide capacity data in terms of work accomplished, or throughput, in various operating systems and workloads environments, rather than in MIPS or instruction execution rates.

Internal Throughput Rate (ITR) and ITR Ratio (ITRR)

LSPR uses the Internal Throughput Rate (ITR) metric to measure work done on different workloads environments. ITR is computed as:

ITR = Units of Work / Processor Busy Time

The “Processor Busy Time” is normalized to 00%1 utilization. “Units of Work” are normally expressed as jobs for batch workloads, and as transactions or commands for on-line workloads.

ITR characterizes processor capacity, since it is a CPU busy time measurement. ITRs are useful for determining the relative capacity between two processors running the exact same workload environment. However, the absolute ITR values from one workload cannot be compared to those of a different workload environment.

The relative capacity between processor for a given workload is done by dividing the ITR of one processor by the ITR of another to produce an ITR ratio, called ITRR. For example, to determine the capacity of processor B relative to that of processor A, the ITR Ratio (ITRR) is calculated as follows:

ITRR = ITR for Processor B / ITR for Processor A

ITR values used in this calculation must be for identical workloads environments.

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IBM 990 manual Large Systems Performance Reference Lspr, Internal Throughput Rate ITR and ITR Ratio Itrr
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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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