Importance

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Abstract

An apparatus for and a method of Dynamic Subchannel Allocation permitting easily field modifiable assignment of Input/Output (I/O) subchannels to I/O channels. Many present day medium-to-large scale computers have an I/O unit(s) with a fixed number of I/O ports or I/O channels for the transmission of information between the computer and peripheral devices. Improvements to these I/O channels, now common in the art, permit multiple peripheral devices to be coupled to the computer through a single I/O channel. Each of these multiple peripheral devices may be said to communicate through an I/O subchannel. A given I/O subchannel designation logically specifies the hardware within the shared I/O channel that is dedicated to communication with the corresponding one of the multiple peripheral devices coupled to that shared I/O channel. The present invention is an improvement which provides for allocation of I/O subchannels to I/O channels in the field rather than at time of manufacture. A random access memory (RAM) is employed which provides the correlation between each I/O subchannel and the I/O channel to which it has been allocated. The RAM is called the Channel Descriptor Stack (CDS). The CDS may be loaded using a variety of techniques. In the preferred embodiment, the CDS is loaded via a specialized processor, called a system support processor (SSP), which also performs those tasks normally associated with system control (e.g., system reconfiguration, interface to the system operator, casualty recovery, etc.).

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First Claim