Figure 6.5: Area comparison between storage area and wire area in the fully buffered architecture.
Figure 6.6: Hierarchical Crossbar ( k =4) built from smaller subswitches ( p =2).
crossbar switch into subswitches where only the inputs and outputs of the subswitch are buffered.
A crossbar switch with k ports that has a subswitch of size p is made up of (k/p) 2 p
each with its own input and output buffers.
By implementing a subswitch design the total amount of buffer area grows as O(vk 2 /p) ,so
by adjusting p ¸ the buffer area can be significantly reduced from the fully-buffered design. This
architecture also provides a natural hierarchy in the control logic — local control logic only needs to
consider information within a subswitch and global control logic coordinates the subswitches.