ECE 2030 10:00am Computer Engineering Fall 2003
4 problems, 3 pages Exam Three Solution 19 November 2003
1
Problem 1 (3 parts, 12 points) Instruction Formats
An instruction format has the following field lengths for R-type and I-type instructions. Answer
the following questions:
opcode RD R
S1 R
S2
8 bits 7 bits 7 bits 7 bits
opcode RD R
S1 immediate value
8 bits 7 bits 7 bits 21 bits
Part A (4 points) How many registers are there? 128
Part B (4 points) How many instruction types are there? 256
Part C (4 points) What is the range of immediate values? -1M to +1M
Problem 2 (3 parts, 32 points) Memory Systems
Part A (12 points) Consider a 64 Mbit DRAM chip organized as 8 million addresses of 8 bit
words. Assume both the DRAM cell and the DRAM chip are square. The column number and
offset concatenate to form the memory address. Using the organization approach discussed in
class, answer the following questions about the chip. Express all answers in decimal.
number of columns K822 1326 ==
column decoder required (n to m) 13 to 8K
type of mux required (n to m) 8K / 8 = 1K to 1
number of muxes required 8
number of address lines in column number log2(8K) = 13
number of address lines in column offset log2(1K) = 10
Part B (10 points) Consider a 256 Mbyte memory system with 64 million addresses of 4 byte
words using 64 Mbit DRAM chips organized as 8 Million addresses by 8 bit words.
word address lines for memory system log2(64M) = 26
chips needed in one bank 4*8 / 8 = 4
banks for memory system 64M / 8M = 8
memory decoder required (n to m) 3 to 8
DRAM chips required 4 * 8 = 32
