All, I would disagree somewhat with the conclusions regarding accuracy and IBIS vs. SPICE models. We must be very careful in how the words "buffer delay" are being used here. For system analyses, many tools define "buffer delay" as the time elapsed between the start of *simulation* and the crossing of a defined measurement voltage, using a defined measurement load. For a well-constructed IBIS model, even using traditional V-t and I-V tables, excellent correlation to SPICE transistor-level models may be obtained for buffer delay in this sense. As a result, IBIS could be -- and is -- used for system timing analysis where the timing equations use buffer delay. Timings for driver outputs relative to an incoming clock signal -- for example, "Tvalid" or "Tco" (Time clock to out) -- could not be directly simulated under traditional IBIS, as the format does not include the data path from the incoming clock node to the driver, to "latch" the signal out. =20 Advanced IBIS models, such as those under IBIS 4.1 and 4.2 using multi-lingual extensions, may contain these driver clock-to-out connections and paths, should the model author choose to include them. A direct comparison of clock-to-out waveforms between this kind of advanced IBIS model and a SPICE transistor model may then be obtained. I hope this helps! - Michael Mirmak Intel Corp. Chair, EIA IBIS Open Forum -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of raj singh Sent: Friday, November 17, 2006 01:34 To: yang@xxxxxxxxxx; si-list@xxxxxxxxxxxxx Cc: liuweidong@xxxxxxxxxx Subject: [SI-LIST] Re: Buffer delay Hspice delays should be accurate and in general more than ibis. Better to use ibis only for SI sims and not for timing. =20 regards Raj yan hang <yang@xxxxxxxxxx> wrote: =20 Hi All, Now I do some board timing simulations . I got the hspice model and ibis model for same buffer. Then I set a test fixture(Ex. Cref=3D15pf,Rref=3D1E6,Vref=3D3.3V),I contrast the simulation result of = buffer delay using hspice model and ibis model. I found there is a little big diffrence between them. So when translate hspice model to ibis model,how to consider about the buffer deley issue?=20 Should I trust the buffer delay value from ibis model simulation? Best Regards. Yan Hang Huawei Technology 086-21=3DA3=3DAD68644808=3DA3=3DAD24043 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu