Brad I think there are ways of getting at the basics of the model vs. measurements. It would be very difficult to measure the predriver current in a large processor but it may be much simpler to measure it in a single gate package. We could perform a series of ever more increasing complexity systems and determine if the models are correct and at what point the measurements get swamped out because of on die and on package bypassing. Regards, Tom Dagostino Teraspeed Labs 9999 SW Wilshire St. Suite 102 Portland, OR 97225 USA 971-279-5325 Office 971-279-5326 FAX 503-430-1065 Cell tom@teraspeed.com www.teraspeed.com <http://www.teraspeed.com/> Teraspeed Consulting Group LLC 16 Stormy Brook Road Falmouth, ME 04105 401-284-1827 From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf Of Bradley Brim Sent: Monday, February 03, 2014 1:58 PM To: Scott McMorrow; Joy Li Cc: Rinsha Reghunath; ibis@eda.org; ibis-users@eda.org Subject: [IBIS-Users] RE: [IBIS] Overclocking effect with composite current Hi Scott, We began to discuss this topic last Friday afternoon at the IBIS Summit in Santa Clara . I understand your points now and then as: (1) Even a transistor-level model may not represent all the relevant behavior of some buffers (2) Converting a transistor-level model to an IBIS model does not address (1) (3) To address (1) a more complex nonlinear transistor-level model is likely required Completely agree with all these points. Your points are not specific to the contribution of the paper cited by Rinsha originally presented in Japan or the follow-up paper presented last Friday in Santa Clara. We believe it is highly interesting and much more than an academic exercise to enable the application of IBIS models instead of transistor-level models. Why? Because for analyses such as SSO where multiple buffers are applied transient circuit simulation times may be literally days when transistor-level models are applied versus minutes when IBIS buffers are applied. Memory consumption is also dramatically reduced. For specific example please refer to Romi Mayder's paper from DesignCon 2013: "Simulating Simultaneous Switching Noise with IBIS v5.0 Models". That paper demonstrates the successful application of BIRDs 95 and 98 for power-aware IBIS models with quantitative comparisons. The paper cited by Rinsha and the similar paper in last Friday's IBIS Summit discuss an extension to over-clocking for such power-aware models. Correlation to physical measurements would help judge the quality of present transistor-level models and guide the development of more complex nonlinear transistor-level models. However, the efforts of enabling more efficient (w.r.t both time and memory) simulations with IBIS models should be judged on correlation between existing transistor-level models and the IBIS macromodels applied in their stead. One could envision producing power-aware IBIS models directly from measurements, but as your colleague Tom Dagostino pointed out last Friday in the IBIS Summit, the required PDN current measurements are extremely difficult (if not impossible) to perform with the required accuracy. The correlation with which you seem to be concerned is less the added detail of overclocking and more one of the core IBIS macromodel itself. I don't recall the effects you cited as specific concern last Friday but another common concern is that pre-driver currents may be from a different power rail than for the analog portion of the buffer. This is not supported by the IBIS topology with its present single-rail power. Suggest you document your specific concerns with transistor-level and IBIS macromodel representation for consideration by IBIS-ATM. Best regards, -Brad From: owner-ibis@eda.org [mailto:owner-ibis@eda.org] On Behalf Of Scott McMorrow Sent: Monday, February 03, 2014 12:50 PM To: Joy Li Cc: Rinsha Reghunath; ibis@eda.org; ibis-users@eda.org Subject: Re: [IBIS] Overclocking effect with composite current joy we at Teraspeed would like to see comparisons between physical measurements and simulation that validate your proposed approach. Without this, your approach is an interesting academic exercise in translating from one approximate modeling format (Spice) to another approximate modeling format (Cadence-IBIS-Spice). You may be solving a problem, but not "the problem." I recognize that "the problem" may not be solved without non-linear modeling. regards, Scott On Mon, Feb 3, 2014 at 2:45 PM, Joy Li <joyli@cadence.com> wrote: Hi Rinsha, At this time, there is no further documentation available publicly. To enable the industry to consolidate on a single approach, we may at some time in the future disclose more details concerning our approach to the IBIS committee for consideration as part of the standard or best practices documentation. Joy Li Cadence From: owner-ibis@eda.org [mailto:owner-ibis@eda.org] On Behalf Of Rinsha Reghunath Sent: Monday, February 03, 2014 9:29 AM To: ibis@eda.org; ibis-users@eda.org Subject: [IBIS] Overclocking effect with composite current Hello, The following paper discusses about the solution for overclocking with composite current: http://www.eda.org/ibis/summits/nov13c/sun.pdf Is there any other documentation further explaining this technique or could someone please give more insight on this? Thanks, Rinsha -- This message has been scanned for viruses and dangerous content by <http://www.mailscanner.info/> MailScanner, and is believed to be clean. -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail mikelabonte@eda-stds.org |or ibis-request@eda-stds.org | |IBIS reflector archives exist under: | | http://www.eda-stds.org/ibis/email_archive/ Recent | http://www.eda-stds.org/ibis/users_archive/ Recent | http://www.eda-stds.org/ibis/email/ E-mail since 1993Received on Mon Feb 3 15:10:30 2014
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