EEL6323-S10-HLec07-MultiStageLE-P2-4spp

H f i d f i p p if d ddp out in c c h on path of path

Info icon This preview shows pages 4–5. Sign up to view the full content.

View Full Document Right Arrow Icon
H F i D f i P p iF D dDP out in C C h on-path of -path on-path CC C b f gh f p dfp g 1
Image of page 4

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
5 Method of Logical Effort 1) Compute path effort 2) Estimate best number of stages 3) Sketch path with N stages 4) Estimate least delay 5) Determine best stage effort 6) Find gate sizes FG B H 4 log NF 1 N D NF P 1 ˆ N f F ˆ i i i out in g C C f Limits of Logical Effort Chicken and egg problem – Need path to compute G – But don’t know number of stages without G Simplistic delay model – Neglects input rise time effects Interconnect – Iteration required in designs with wire Maximum speed only – Not minimum area/power for constrained delay Summary Logical effort is useful for thinking of delay in circuits – Numeric logical effort characterizes gates – NANDs are faster than NORs in CMOS – Paths are fastest when effort delays are ~4 – Path delay is weakly sensitive to stages, sizes – But using fewer stages doesn’t mean faster paths – Delay of path is about log 4 F FO4 inverter delays (NxFO4 delay) – Inverters and NAND2 best for driving large caps
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern