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

6947ch03.fm

Depending on the number of I/O slots plugged into the cage, there may be from one to seven eSTI-M cards plugged into a z990 I/O cage. The eSTI-M card can be installed or replaced concurrently.

STI-2 Extender card

The STI-2 Extender card (Feature Code 3992) takes the 2 GB/sec link from an MBA’s STI and creates two secondary 333 MB/sec STI links, which are used to connect ICB-2 links. ICB-2 are supported only for connection to G5/G6 servers

The number of STI-2 Extender cards depends on the number of ICB-2 links in a configuration. Usually the number of STI-2 Extender cards is half the number of ICB-2 links, but for availability reasons, two ICB-2 links are connected to two STI-2 Extender cards, each one having one active ICB-2 link port.

The maximum number of STI-2 Extender cards in a z990 server is 4 cards, resulting in up to 8 ICB-2 ports. All of them can be installed in a single I/O cage. The STI-2 Extender card can be installed or replaced concurrently.

STI-3 Extender card

The STI-3 Extender card (Feature Code 3993) takes the 2 GB/sec link from an MBA’s STI and creates two secondary 1 GB/sec STI links, which are used to connect ICB-3 links.

The number of STI-3 Extender cards depends on the number of ICB-3 links in a configuration. Usually the number of STI-3 Extender cards is half the number of ICB-3 links, but for availability reasons, two ICB-3 links are connected to two STI-3 Extender cards, each one having one active ICB-3 link port.

The maximum number of STI-3 Extender cards in a z990 server is 8 cards, resulting in up to 16 ICB-3 ports. All of them can be installed in a single I/O cage. The STI-3 Extender card can be installed or replaced concurrently.

3.2.3 Balancing I/O connections

The z990 server’s multi-book structure results in multiple MBAs, therefore there are multiple STI sets. This means that an I/O distribution over books, MBAs, STIs, I/O cages, and I/O cards is desirable for both performance and availability purposes.

The STI links balancing across a book’s MBAs, I/O cages, and I/O cards is done by IBM at the server’s initial configuration time. Follow-on upgrades of the initial server configuration, including additional book(s) and/or I/O cage(s), may undo the balance of the original STI links distribution.

The optional upgrade feature STI Rebalance (Feature Code 2400) can be requested at upgrade configuration time to rebalance STI links across the new total number of books and I/O cages. However, STI rebalancing is disruptive, requiring a server outage.

The processor I/O ports balancing across I/O cards, I/O cages, STI links, and a book’s MBAs is done by the customer at I/O definition time. This is done by either the use of the CHPID Mapping Tool to assign CHPIDs to PCHIDs, or manually by assigning installed PCHIDs to CHPIDs. The use of the CHPID Mapping tool is strongly recommended.

The balancing may also be affected by the STI Rebalance feature (FC 2400) after a server upgrade.

Chapter 3. I/O system structure

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IBM 990 manual Balancing I/O connections, STI-2 Extender card, STI-3 Extender card
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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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