Question

In a MIPS processor I/O address space 0xffff0000 to 0xffffffff is reserved for memory-mapped I/O. Assuming that an I/O device needs 3, 1, and 4 32-bit words for control, status, and data registers respectively, how many I/O devices can be supported?

a) 16
b) 32
c) 64
d) 128

Answer 1

Each I/O device requires 8 32-bit words, equaling 32 bytes of space. With 65536 bytes available, a total of 2048 I/O devices could be theoretically supported, which is not among the provided answer options.

Step-by-step explanation:

The student is asking about the address space allocation for I/O devices within a MIPS processor. The address space reserved for memory-mapped I/O is from 0xffff0000 to 0xffffffff. Each I/O device requires 3 + 1 + 4 = 8 32-bit words for its control, status, and data registers, respectively. Since each 32-bit word occupies 4 bytes, each device needs 8 * 4 = 32 bytes. The total addressable space is 0xffffffff - 0xffff0000 + 1 = 65536 bytes. Dividing this by the space required per device (32 bytes), we can support 65536 / 32 = 2048 devices

However, the options provided in the question do not include this number, indicating that there's likely a constraint or error in the question's options.