ECE 2030 C Computer Engineering Spring 2001
5 problems, 5 pages Exam Three 19 April 2001
1
Problem 1 (3 parts, 24 points) Memory Systems
Imagine using a 4 Mbit DRAM organized as 1 million addresses of 4-bit words to build three memory
systems. The following three parts consider memory systems built using this chip.
Part A (8 points) Consider a 16 Mbit memory system organized as 4 million addresses of 4-bit words.
number of chips needed in one bank 4bits/bank / 4bits/chip = 1 chip/bank
number of banks for memory system 4M/system / 1M/bank = 4 banks/system
memory decoder required (n to m)2 to 4
number of DRAM chips required 1 chip/bank * 4 banks/sys = 4 chips
Part B (8 points) Consider a 16 Mbit memory system organized as 1 million addresses of 16-bit words.
number of chips needed in one bank 16bits/bank / 4bits/chip = 4 chips/bank
number of banks for memory system 1M/system / 1M/bank = 1 banks/system
memory decoder required (n to m)not required
number of DRAM chips required 4 chip/bank * 1 bank/sys = 4 chips
Part C (8 points) Consider an 256 Mbit memory system organized as 32 million addresses of 8-bit
words.
number of chips needed in one bank 8bits/bank / 4bits/chip = 2 chips/bank
number of banks for memory system 32M/system / 1M/bank = 32 banks/system
memory decoder required (n to m)5 to 32
number of DRAM chips required 2 chip/bank * 32 banks/sys = 64 chips
Problem 2 (1 part, 10 points) Instruction Formats
Suppose a datapath has three operand busses (two source, one destination), 100 instruction types, and
64 registers where each register is 32 bits wide. Immediate operands can be in the range of ±4K.
Determine the following values for the resulting instruction format. For the last two questions, assume the
same operand number and types used in the MIPS format.
bits needed to specify an opcode 7
bits needed to specify a register operand 6
bits needed to specify an immediate operand 13
bits needed to specify an R-format instruction 7 + 6 + 6 + 6 = 25
bits needed to specify an I-format instruction 7 + 6 + 6 + 13 = 32
