(Spring 2004 - Wawrzynek & Patterson): "1) Power and Energy in Microprocessors a) Give us a metric for expressing energy efficiency of a microprocessor for a particular workload. (would expect MIPS/watt or joules/instruction, ...) b) If I gave you a microprocessor and that workload, how would you measure its average energy efficiency? (needs to understand P=IV and think about using a current meter. Then measure time and number of instructions, ..., ) c) What are the factors that effect/determine power consumption in this experiment and how could you influence each factor? (P = Cv^2f, c is process and wire lengths, v is process and user set,...) 2) Microprocessor Limitaions a) What do you think some of the technological limitations to increasing microprocessor performance in the next 3 to 7 years? b) How do recent 80x86 microprocessor designs match up to those limitations? c) How would you expect such limitations will change the microarchitectures in this time period? 3) Networks of processors Suppose you were engineering a multiprocessor on a chip (a homogeneous array of simple processing units with local memory each). Think about what structure you would use to connect the processors together. a) What network topologies would you consider and why? (Should be able to describe meshes, trees, busses, xbar, etc.) What factors would you consider in choosing one versus another? What other factors would come into the design? (need to consider area cost, control and routing complexity, packet switched or circuit swithed, cross-section bandwidth, scaling) How would you go about determining the best design for this network?"
(Fall 2003 - Culler & Kubiatowicz): "Q1: For the first question, we were looking for concise definition of precise interrupts, followed by clear illuminations of mechanisms for achieving precise interrupts in both 5-stage and out of order pipelines. Q2: The second question focused on evaluating design tradeoffs. It centered on energy efficiency. Q3: The third question focused on instruction set design. The specific context was communication on a chip based multiprocessor. We asked for a list of possible forms of communication and then to discuss how to extend the ISA for each. Q4: For the final question, we were looking to explore the design space for a NAS (network attached storage) system."
(Fall 2002 - Culler & Patterson): "Q1: Vector processing Q2: Power and energy Q3: Errors in computers Q4: Branch prediction"
(Spring 2002 - Kubiatowicz & Wawrzynek): "Q1: RISC/CISC Q2: Power consumption Q3: Networked multiprocessors Q4: Multi-threading"
(Fall 2001 - Kubiatowicz & Patterson): "Q1: modern processor design Q2: trace caches Q3: VLSI scaling Q4: high-transaction rate server"
(Spring 2001 - Wawrzynek & Kubiatowicz): "Q1: What are precise interrupts? Why are they useful? Discuss how to implement precise interrupts in a modern processor (superscalar, out-of-order) of your choice. What is branch prediction? Why is it useful? How does it fit into your example processor? What other things do people try to predict? Q2: Draw the floorplan for a processor (real or imaginary but realistic). Include the major functional blocks and their approximate sizes. Imagine you now have a merged DRAM/logic process. Assuming an identical organization and memory hierarchy, how would this affect the floorplan? How would the floorplan differ if you could change the organization or memory hierarchy? Q3: What is memory coherency in multiprocessors? Discuss coherency in a snoopy bus model. Describe a series of reads and writes in this model. What is consistency? What is sequential consistency and how can it be modelled? Describe the limitation of snoopy-based coherency models? What is/are the solutions? Describe a series of reads and writes in that model? Q4: We want to create a network router from a standard PC. (For our purposes, a router will input a packet, examine the packet, make a decision about where to route the packet based on stored state, and send the packet out that port.) Draw a diagram of this system and trace a packet through this system. How do we determine the number of ports that a single PC can support? What is the bottleneck? How do you justify this? Estimate various execution times, bandwidths, and latencies."
(Fall 2000 - Wawrzynek & Patterson): "Q1: Identify the critical paths in microprocessor design. What is the effect of carry logic on adder delay? Discuss fast adder techniques. Q2: Discuss issues related to disk drives, trends, today's spec, and future specs. Reason about read times for an entire disk and how this relates to RAIDs and other disk arrays. Q3: Discuss the basic issues involved with system implementation alternatives. Q4: Identify some out-of-order (OOO) execution processors. Select one and describe its operations."
(Spring 2000 - Wawrzynek & Kubiatowicz): "Q1: Discuss the distinctions between RISC and CISC; compare and contrast the advantages of one over the other. Discuss whether the RISC/CISC distinction is still valid today. Q2: Discuss the detailing of overheads of message communication. How would you optimize communication? Q3: Account for the large difference in energy observed between solving a problem with custom hardware vs. a general purpose processor. List some of the metrics one might use to decide between a custom ASIC, an FPGA, or a general purpose processor. Q4: What is the cache-coherence problem? What are the definitions of sequential consistency? Discuss the details of snoopy protocols. and about the typical bus bandwidth. Estimate the maximum number of processors that would fit on a bus."
(Fall 1999 - Wawrzynek & Kubiatowicz): "Q1. Describe precise interrupt. Why is it useful? Describe exactly how you would implement it on a 5 stage pipeline. Draw a rough block diagram of an out-of-order execution processor. Describe how you implement precise interrupt with respect to that block diagram. What happens to the precise interrupt scheme when there is branch mispredictions? Q2: Given a very simple processor with no cache, no floating point unit, single issue, everything in order, pipelined processor, estimate the number of transistors it will use. Given the number of transistors you just came up with, can you implement it using some state-of-the art FPGA? What is the rough capacity of the FPGA? What are some pros and cons of implementing such a processor on a FPGA if it is possible? Why would someone ever want to do such thing in the real world? Q3: Suppose you want to implement a multiprocessor over the conventional network (like ethernet), describe all the mechanisms you need to pass a message from one user to another user. Estimate the time it takes for the message to go through each part of the process. Given the time you just estimated, is it fast enough to meet the need of implementing multiprocessor? How can you improve the speed? How can you protect users from interfering each other if they have control over the network hardware? Q4: Define energy efficiency. Given that you have a 4-way super-scalar processor, a program, and the data input, describe how (including hardware setup) you can measure the energy efficiency of this processor. What would be the issue if you want to compare this energy efficiency number with other processors? If you are a chief architect, what kind of processor you would design to optimize energy efficiency?"
(Spring 1999 - Patterson & Kubiatowicz): "Q1: What are the causes of cache misses (three C's)? Describe how to remove these. Under what circumstances would they be advantageous? Q2: What is the definition of precise interrupts and the implementation of precise interrupts in a five-stage pipeline? Discuss modern superscalar processors. Q3: Discuss some of the issues behind the replacement of buses with routers. What are some advantages of router-like architectures? Q4: Discuss computational paint."
(Fall 1998 - Patterson & Kubiatowicz): "Q1: What is the definition of precise interrupts and the implementation of precise interrupts in a five-stage pipeline? Discuss modern superscalar processors. Q2: What are the consequences of increased wire delay? How would you evaluate ambiguous design alternatives? Q3: Discuss the basic message communication path. Why would a separate network be needed to avoid protocal overhead? Q4: (A database design problem was given.) Calculate the numbers of disks and CPUs for 100% utilization as well as bus organization. What does the queueing theory suggest?"
August 2000