ECE 2030 11:00am Computer Engineering Fall 2003
4 problems, 3 pages Exam Three Solution 19 November 2003
1
Problem 1 (3 part, 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
12 bits 9 bits 9 bits 9 bits
opcode RD R
S1 immediate value
12 bits 9 bits 9 bits 28 bits
Part A (4 points) How many registers are there? 512
Part B (4 points) How many instruction types are there? 4K
Part C (4 points) What is the range of immediate values? -127M to +128M
Problem 2 (3 parts, 32 points) Memory Systems
Part A (12 points) Consider a 4 Gbit DRAM chip organized as 512 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 K6422 1632 ==
column decoder required (n to m) 16 to 64K
type of mux required (n to m) 64K / 8 = 8K to 1
number of muxes required 8
number of address lines in column number log2(64K) = 16
number of address lines in column offset log2(8K) = 13
Part B (10 points) Consider a 256 Mbyte memory system with 64 million addresses of 4 byte
words using 16 Mbit DRAM chips organized as 4 million addresses by 4 bit words.
word address lines for memory system log2(64M) = 26
chips needed in one bank 4*8 / 4 = 8
banks for memory system 64M / 4M = 16
memory decoder required (n to m) 4 to 16
DRAM chips required 8 * 16 = 128
