Abstract: A computer system I/O node. An input/output node for a computer system includes a first receiver unit configured to receive a first command on a first communication path and a first transmitter unit coupled to transmit a first corresponding command that corresponds to the first command on a second communication path. The input/output node also includes a second receiver unit configured to receive a second command on a third communication path and a second transmitter unit coupled to transmit a second corresponding command that corresponds to the second command on a fourth communication path. Further, the input/output node includes a bridge unit coupled to receive selected commands from the first receiver and the second receiver and configured to transmit commands corresponding to the selected commands upon a peripheral bus.

Abstract: A tagging and arbitration mechanism in an input/output node of a computer system. A mechanism for tagging commands in an input/output node of a computer system includes a tag circuit configured to receive a plurality of control commands. The tag circuit may also be configured to generate a tag value for each of the control commands. The tagging mechanism may also include a buffer circuit which is coupled to the tag circuit. The buffer circuit may include a plurality of buffers each corresponding to a respective virtual channel of a plurality of virtual channels for storing selected control commands that belong to the respective virtual channel. Further the tagging mechanism may include an arbitration circuit that is coupled to the buffer circuit and is configured to arbitrate between the plurality of buffers depending upon the tag value for each of the control commands.

Abstract: A virtual channel buffer bypass in a computer system input/output node. A control unit of an input/output node for a computer system includes a buffer circuit configured to receive control commands. The buffer circuit may include a plurality of buffers each corresponding to a respective virtual channel of a plurality of virtual channels for storing selected control commands that belong to the respective virtual channel. The buffer circuit may also be configured to determine whether each of the plurality of buffers is empty prior to storing a particular control command corresponding to a given one of the plurality of buffers. In addition, the buffer circuit may be configured to cause the particular control command to bypass the given one of the plurality of buffers in response to determining that each of the plurality of buffers is empty.