Interconnection network parameters

flitsize

This parameter specifies the number of bytes in each network flit, which is equivalent to the width of the network in bytes. Defaults to 8.

flitdelay

This parameter gives the latency for each flit to pass through a network switch, in processor cycles. Defaults to 4 (with a 300 MHz processor, this delay indicates a 13 ns flit latency).

arbdelay

This parameter gives the delay invoked by arbitration at each network multiplexer for the head flit of any packet. Defaults to 4.

pipelinedsw

This parameter allows the use of pipelined network switches, in which the flit delay of multiple flits can be partially overlapped. With pipelined switches, the flit delay for each successive flit in a packet will begin pipelinedsw number of cycles after the start of the previous flit delay. If the number 0 or a number greater than the flit delay is specified here, the switches are not pipelined. Defaults to 2 (with an assumption of 300 MHz processors, this implies a 150 MHz network cycle for a fully pipelined switch.)

netbufsize

This parameter specifies the number of flits that can be buffered in each network switch. Defaults to 64.

netportsize

This parameter specifies the network interface buffer sizes, in packets. Each node has 2 network interfaces, one for sending messages to the network, and one for receiving messages from the network. Each network interface has 2 port queues (described in Section 12.1) connecting the network interface to the bus (one for requests and one for replies). This parameter specifies the number of entries available in each port queue. This parameter is also used to specify the number of internal buffer entries in each network interface for actually sending messages to the network or receiving messages from the network. Each network interface has two internal buffers: one for requests and one for replies. The total number of packets in these two internal buffers is set by the parameter netportsize, split evenly between requests and replies. The network interface and interconnection network is described more thoroughly in Chapter 15.3.