S/390 CMOS server I/O: The continuing evolution

IBM has developed a strategy to achieve the high I/O demands of large servers. In a new environment of industry-standard peripheral component interconnect (PCI) attached adapters conforming to open I/O interfaces, S/390® has developed an efficient method of quickly integrating disk storage, communications, and future adapters. Preserving the S/390 I/O programming model and the high level of data integrity expected in S/390 products and reducing development cycle time and resources have further constrained design options. At the same time, S/390 developers have redesigned the traditional I/O components into the latest chip technologies. The developers have also designed a new internal link (STI) to meet the increased I/O bandwidth and connectivity required by the high processor performance of the third and fourth generations of S/390 CMOS servers. This paper describes this strategy and how it has led to systems that retain the differentiating features of S/390 products.