Re: [SI-LIST] : receiver jitter

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From: Jonathan Dowling (jdowlin2@yahoo.com)
Date: Tue Jan 18 2000 - 17:57:18 PST


Newbies: Time for a history lesson...

I would be willing to bet Chris' sentiments today were issued
verbatim by critics of behavioral modeling at the folks who
developed behavioral simulators in the 1980's (or before).
Proponents of SPICE have long criticized IBIS-like simulators,
even when signal quality not an issue (only timing).

If we go back in time we would hear:
"We are going to be running at 4MHz this year. You can't correctly
predict timing with a behavioral model. This is 5V logic. You will
have to use SPICE. Specifically, you can't model the receiver well
enough."

The true test is time-to-market. Almost without exception, all
the companies that excel at time-to-market in the digital world
have boatloads of behavioral simulator licenses. Intel is the
best example of this fact because they make the most money.
Their behavioral simulator licenses number in the 100's. If you
claim your company excels at time-to-market without behavioral
simulation, I claim your company is not as successful as Intel.

Rambus's SPICE bigotry certainly contributed to their poor
time-to-market showing last year. Maybe they don't have a single
behavioral simulator in-house. They were generous enough to make
an IBIS model, but it was pooh-poohed by the 'experts' who claimed
(on this reflector list) that only the SPICE model would do.
Simulation with the simple IBIS model is enough to show timing
marginality at 800MT/s. (By the way, it looks great at 600MT/s
if you're lucky enough to avoid the resonances.)

Jonathan Dowling

--- Chris Cheng <hycheng@3pardata.com> wrote:
> as core and signal swing getting smaller and smaller, this
> problem is getting worst. compound this with source sync
> buses where the strobes and data can behave differently
> (true differential vs. pseudo differential), i believe
> predicting the response of the receiver under different
> waveforms input will be as important as simulating
> the propagation of signal in the interconnect
> environment. this will be the final nail in the coffin for
> behavioral models like ibis which is totally incapable of
> handling such analysis. i have seen pitiful attempts to
> qualitatively describe it in ring back or edge rate
> extrapolation but without the ability to simulate the
> receiver behavior, those specs are just fancy words with
> no meaningful insight into the response of the true
> receiver.
> can i spell SPICE again.
> chris
>

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