ECE 2030 2:00pm Computer Engineering Spring 2001
4 problems, 3 pages Exam Three 18 April 2001
1
Problem 1 (3 parts, 30 points) Memory Systems
Imagine using a 16 Kbit DRAM (the dynamic memory chip of choice when I graduated from
Tech) organized as 4 thousand addresses of 4-bit words to build three memory systems. The
following three parts consider memory systems built using this chip.
Part A (10 points) Consider 64 thousand addresses of 8-bit words memory system.
number of chips needed in one bank 8bit/bank / 4bits/chip = 2 chips/bank
number of banks for memory system 64K/system / 4K/bank = 16 banks/system
memory decoder required (n to m) 4 to 16
number of DRAM chips required 2 chips/bank * 16 banks/sys = 32 chips
Part B (10 points) Consider 1 million addresses of 16-bit words memory system.
number of chips needed in one bank 16bit/bank / 4bits/chip = 4 chips/bank
number of banks for memory system 1M/system / 4K/bank = 256 banks/system
memory decoder required (n to m) 8 to 256
number of DRAM chips required 4 chips/bank * 256 banks/sys = 1024 chips
Part C (10 points) Consider 256 million addresses of 32-bit words memory system.
number of chips needed in one bank 32bit/bank / 4bits/chip = 8 chips/bank
number of banks for memory system 256M/system / 4K/bank = 64K banks
memory decoder required (n to m) 16 to 64K
number of DRAM chips required 8 chips/bank * 64K banks/sys = 512K chips
Problem 2 (1 part, 15 points) Instruction Formats
An ancient Egyptian hieroglyphic tablet has been found which may be the earliest record of an
instruction set architecture (perhaps alien?). The example shown below has all fields shown with
zeros. Do your best to interpret its meaning and answer the questions below.
000 000 000 000 000 000 000 000 000 000 000 000
opcode dest. reg. source 1 reg. immediate value
What is the maximum number of opcodes? 29 = 512
What is the number of registers? 26 = 64
What is the range of the signed immediate value? 215 = ±16K
How many bits would an R-type instruction use? 9 + 6 + 6 + 6 = 27
