Question

Figure B.8.8 on page B-55 illustrates the implementation of the register file for the MIPS datapath. Pretend that a new register file is to be built, but that there are only two registers and only one read port, and that each register has only 2 bits of data. Redraw Figure B.8.8 so that every wire in your diagram corresponds to only 1 bit of data (unlike the diagram in Figure B.8.8, in which some wires are 5 bits and some wires are 32 bits). Redraw the registers using D flipflops. You do not need to show how to implement a D flip-flop or a multiplexor.

Short answer

The figure B8.8 would be redrawn for 2 -bit register file using D flipflops is as follows:

Step-by-step solution

Determine register file

A register file will have two read ports and the one write port. Five inputs will be given to the register file, whereas the outputs will be two. A register file will have the set of registers that can be read and written. The array of registers can be build using the D flip-flops. For reading register there will be no state change occur. For writing, it needs three inputs such as register number, write data and the clock signal.

Redraw the fig B.8.8. by using D flip-flops

Given that the new register file has two registers and only one read port. Each registers have only 2 bits of data.

Refer Fig B.8.8 to know the implementation of a register file.

The redrawn diagram using D flip-flops with one bit data.