Recollections of the "The Father of SPICE" Larry Nagel

From LTwiki-Wiki for LTspice

On Fri, 19 Jul 2013 at 10:47 AM, <analogspiceman> wrote:

Hello Dr. Nagel,

I am a user and fan of SPICE (LTspice, to be precise) and a major contributor to the LTwiki and the LTspice users' group.

I have compiled a bulleted history of SPICE and the road to its popularization (culminating in LTspice).  Please see:

I hope I have the facts straight and would be happy to take any suggestions for corrections that you might have (if you are so inclined).  The wiki is a work in progress and I intend to fill it out with references to your website and pertinent publications.  Also, with your permission, the owner and host of the LTwiki would likely be willing to directly archive copies of some of your publications.

Best Regards

On Tue, 30 Jul 2013 at 12:22 PM, Larry Nagel wrote:

I apologize for taking so long in responding to your inquiry.  I've had a lot of consulting work lately, and then I just finished with a visit from grandchildren from Boston.  The dust hasn't yet settled!

First of all, let me congratulate you on doing an excellent job on the history of SPICE.  I don't know whether you were ever connected with the SPICE effort at Berkeley, but you certainly seemed to sort out most of the facts in a very clear and concise manner.  Job well done!

Here are a few comments/corrections:

  • CANCER wasn't a derivative of the class project program, it WAS the class project program.  After the class project was over, CANCER became my Master's Project, and Ron Rohrer was my research adviser for my Master's program.  You are correct that there was controversy between Don Pederson and Ron Rohrer regarding whether CANCER code was proprietary.
  • After I finished up my Master's degree with Ron Rohrer, and after Ron decided to leave Berkeley, and after a summer job working with Ron Rohrer at SofTech in Boston, I started on my PhD program with Don Pederson in the fall of 1971.  It was then that CANCER was renamed SPICE and version 1 of SPICE was released to friendly users shortly thereafter.
  • You are correct that CANCER and SPICE 1 did not use Modified Nodal Analysis, but they did implement both ideal voltage sources and inductors using a row-swap algorithm in addition to Nodal Analysis.
  • SPICE was officially released to the world in May 1972 and was officially announced at the 16th Midwest Symposium on Circuit Theory in April, 1973.  By this time SPICE contained the both Ebers-Moll and Gummel-Poon bipolar models, Shichman-Hodges JFET and MOSFET models, flicker noise models, sensitivity analysis using the adjoint network, distortion analysis of weakly nonlinear bipolar circuits using Volterra series models and the adjoint network, and numerous improvements intended to make the program more user-friendly and bulletproof.
  • There is this persistent rumor that Ellis Cohen added dynamic memory allocation to SPICE 2.  Both Ellis and I will tell you that it was I who added dynamic memory allocation to SPICE 2.  It's in my thesis.  Ellis was my roommate at the time and we certainly had many discussions about how to best implement dynamic memory allocation, but it was I who punched the cards and debugged the monster.  I will never again try to implement dynamic memory allocation in a FORTRAN program!
  • SPICE 2B had subcircuits (it's in my thesis) but Ellis Cohen reworked the implementation in his version of SPICE.  Ellis was solely responsible for the addition of poly sources and transmission lines.
  • I think that Ellis Cohen would agree with me that SPICE 2G6 was mainly the work of Andrei Vladimirescu.  Much of the MOSFET modeling work in SPICE 2G6 was due to Sally Liu.  The statement that "Ellis Cohen becomes primary contributor with later help from Andrei Vladimirescu" may be a little unfair to Andrei.
  • The P in PSpice stands for Personal Computer, not micro Processor.  PSpice was the first commercial simulator that ran on a personal computer.  PSpice may have originally evolved from SPICE2, but quickly migrated to the SPICE3 code base.  I don't know if there ever was a FORTRAN version of PSpice.

I hope this helps you in your history exercise.  It's always fun delving back forty years ago in my lifetime!



Laurence Nagel
Omega Enterprises Consulting
251 Stanford Avenue
Kensington, CA 94708
(510) 558-0842

On Fri, 2 Aug 2013 at 10:01 AM, <analogspiceman> wrote:

Thanks ever so much for your comments!  It really is best to get the facts directly from "the horse's mouth" so to speak. :-)  I have now incorporated your comments and corrections into the wiki's history page.  In case something got garbled in the process, please don't hesitate to provide further corrections.

Best Regards