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4 problems, 4 pages Exam Three 19 April 2000
Instructions: This is a closed book, closed note exam. Calculators are not permitted. If you have a question, raise your hand and I will come to you. If you finish early, please check your work until the bell rings so as not to disturb others that are still working. Please work the exam in pencil and do not separate the pages of the exam. For maximum credit, show your work. Good Luck!
Your Name ( please print ) ________________________________________________
1 2 3 4 total
4 problems, 4 pages Exam Three 19 April 2000
Problem 1 (3 parts, 30 points) Memory Systems
Imagine using a 256 Mbit DRAM organized as 32 million addresses of eight bit words to build three memory systems. The following three parts consider memory systems built using this chip.
Part A (10 points) Consider a 128 Mbyte memory system organized as 32 million addresses of 32 bit words.
number of chips needed in one bank number of banks for memory system
memory decoder required ( n to m ) number of DRAM chips required
Part B (10 points) Consider a 512 Mbyte memory system organized as 64 million addresses of 64 bit words.
number of chips needed in one bank number of banks for memory system memory decoder required ( n to m )
number of DRAM chips required
Part C (10 points) Consider an 8 Gbyte memory system organized as 256 million addresses of 256 bit words.
number of chips needed in one bank number of banks for memory system memory decoder required ( n to m )
number of DRAM chips required
Problem 2 (1 part, 15 points) Instruction Formats
Suppose a datapath has three operand busses (two source, one destination), 256 instruction types, and 128 registers where each register is 64 bits wide. Immediate operands can be in the range of ±128K. 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
bits needed to specify a register operand
bits needed to specify an immediate operand
bits needed to specify an R-format instruction
bits needed to specify an I-format instruction
4 problems, 4 pages Exam Three 19 April 2000
Problem 4 (5 parts, 30 points) Microcode Reverse Engineering
The microcode fragment below comes from a color scanner control program that runs on the datapath discussed in class (see exam handout). The scanner samples red, blue, and green intensities for each pixel (spot) of the image. These intensities are converted into ten bit unsigned values using an analog to digital converter. For each question below, describe the meaning of the specified microcode cycle. Unfortunately, don’t care values (X) have been converted to zeros. For maximum points, be as specific and concise as you can (e.g., list shift types, amounts, and directions, logical functions, memory addresses and operations, etc.)
Example: Describes the operation that occurs during cycle 8. R2 <- R0 + R2 or R0 and R2 are added and stored in R
cycle X Y Z rwe im en im va au en -a/s lu en lf su en st ld en st en r/-w msel 1 0 0 0 1 1 100 0 0 1 C 0 0 0 0 0 0 2 0 0 0 1 0 0 0 0 0 0 0 0 1 0 1 1 3 0 0 2 1 1 3FF 0 0 1 8 0 0 0 0 0 0 4 0 0 0 1 1 A 0 0 0 0 1 0 0 0 0 0 5 0 0 1 1 1 3FF 0 0 1 8 0 0 0 0 0 0 6 1 2 2 1 0 0 1 0 0 0 0 0 0 0 0 0 7 0 0 0 1 1 A 0 0 0 0 1 0 0 0 0 0 8 0 2 2 1 0 0 1 0 0 0 0 0 0 0 0 0
Part A (5 points) Describes the operation that occurs during cycle 1 (be specific).
Part B (5 points) Describes the operation that occurs during cycle 2 (be specific).
Part C (5 points) Describes the operation that occurs during cycle 4 (be specific).
Part D (5 points) Describes the operation that occurs during cycle 5 (be specific).
Part E (10 points) Describes the operation of this microcode fragment (be specific).
