DD Exam 3: Comprehensive Study Guide and Review
In general, FPGA synthesis tools convert tri-state buffers into multiplexors. Briefly explain why the tools
perform this conversion. - correct answer ✔✔FPGAs don't internally have tri-state buffers
How long does it take for a metastable signal to stabilize? - correct answer ✔✔Unknown
Write enables for a bus often use a one-hot encoding, where at most one source is assumed to be given
access at any time. For a 4-source bus, what component can be added to guarantee this assumption is
always true? - correct answer ✔✔2:4 decoder
Explain why a dual-flop synchronizer provides a shorter mean-time between failures as the destination
clock frequency increases. - correct answer ✔✔One cycle is a shorter amount of time at higher
frequencies
Describe when to use a FIFO instead of a handshake synchronizer - correct answer ✔✔When
bandwidth/throughput is important
Explain why a dual-flop synchronizer can be used to synchronize multiple bits when only a single input
bit changes - correct answer ✔✔The output is either the previous value or the correct value, but never
an incorrect value
What is the name of the emerging area of research that looks at sacrificing accuracy to improve
performance and/or energy? - correct answer ✔✔Approximate computing
FPGA virtualization addresses - correct answer ✔✔Productivity, computing time, and application
portability
For the MIPS, a function call is usually implemented with what instruction? - correct answer ✔✔JAL
For the MIPS, a return from a function uses what instruction? - correct answer ✔✔JR
In general, FPGA synthesis tools convert tri-state buffers into multiplexors. Briefly explain why the tools
perform this conversion. - correct answer ✔✔FPGAs don't internally have tri-state buffers
How long does it take for a metastable signal to stabilize? - correct answer ✔✔Unknown
Write enables for a bus often use a one-hot encoding, where at most one source is assumed to be given
access at any time. For a 4-source bus, what component can be added to guarantee this assumption is
always true? - correct answer ✔✔2:4 decoder
Explain why a dual-flop synchronizer provides a shorter mean-time between failures as the destination
clock frequency increases. - correct answer ✔✔One cycle is a shorter amount of time at higher
frequencies
Describe when to use a FIFO instead of a handshake synchronizer - correct answer ✔✔When
bandwidth/throughput is important
Explain why a dual-flop synchronizer can be used to synchronize multiple bits when only a single input
bit changes - correct answer ✔✔The output is either the previous value or the correct value, but never
an incorrect value
What is the name of the emerging area of research that looks at sacrificing accuracy to improve
performance and/or energy? - correct answer ✔✔Approximate computing
FPGA virtualization addresses - correct answer ✔✔Productivity, computing time, and application
portability
For the MIPS, a function call is usually implemented with what instruction? - correct answer ✔✔JAL
For the MIPS, a return from a function uses what instruction? - correct answer ✔✔JR
