Re: [IBIS-Users] Re: [IBIS] RE: BIRD95: Power Integrity Analysis Using IBIS

Hi Arpad,

Thanks for your comments. Please see my replies in your e-mail. Thanks.

Best regards,

Zhiping
----- Original Message -----
From: "Muranyi, Arpad" <arpad.muranyi@intel.com>
To: <ibis@eda.org>; "ibis-users" <ibis-users@eda.org>
Sent: Wednesday, January 05, 2005 4:03 PM
Subject: RE: [IBIS-Users] Re: [IBIS] RE: BIRD95: Power Integrity Analysis
Using IBIS

> Zhiping,
>
> I would like to comment on your paragraph on the gate modulation
> effect. I think your statement "For the current IBIS, the power
> is assumed to be perfect" is not entirely true. Think about the
> "Vcc relative" IV curves and the package modeling, for example.
> The origin of each IV curve is associated with a corresponding
> [XYZ Reference] keyword. Using appropriate package parasitics and
> [Pin Mapping], these reference voltages are allowed to bounce as
> the buffers are switching. So the power of the buffers do not
> have to be perfect in the IBIS world.

Yes. I understood that some EDA tools could let IBIS to simulate the SSO,
but my concern is that their results may not be correct. Besides the "gate
modulation effect" which we talked about, my personal understanding is that
even the SSO noice can be simulated with exisiting IBIS model, but the noise
coupling mechanism from power to signal pin may not be implemented or not
implemented correctly. In another word, could the power noise impact on the
rising/falling edge in IBIS simulation match to the HSPICE simulation? I
could be wrong and I am working on some simulations in HSPICE to verify it.

>
> It is a different story that the strength of the buffer is not
> modulated in most IBIS simulators based on the bouncing rail
> voltages. But this capability would not be very difficult to
> add. We could get started by just adding two parameters to
> the IBIS specification which would have the same meaning that
> I mentioned before in the HSPICE B-element.

I just read the HSPICE manual on these two parameters (spu_scal and
spd_scal) you mentioned. I didn't see any detailed explainations on how to
use them. Do you have any examples to show their impact on the IBIS
performance? Personally I feel it may improve the IBIS performance, but it
still can not completely solve the "gate modulation effects" in IBIS.

>
> The first thing to decide is whether these should be part of
> BIRD95. If yes, we can continue on this thread and discuss
> how it should be defined. If not, we can start another thread
> and BIRD to do it separately. Any takers to write it up?
>
> Arpad
> =================================================================
>
> -----Original Message-----
> From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf
Of Zhiping Yang
> Sent: Wednesday, January 05, 2005 3:30 PM
> To: Roy Leventhal; twesterh@cisco.com; ibis@eda.org; 'ibis-users'
> Subject: [IBIS-Users] Re: [IBIS] RE: BIRD95: Power Integrity Analysis
Using IBIS
>
> Hi Roy,
>
> Very well said about the IBIS model.
>
> For current BIRD95, our intention was not to completely solving the power
> integrity problem in one proposal. As a first step to improve the IBIS
> model capability and accuracy in SSO simulation, we proposed to add IvsT
> information of the I/O power pin into existing IBIS model. We think this
> IvsT table will provide enough info on Xbar current, Pre-driver current
from
> VDDQ, internal termination current and embedded decoupling current within
> I/O cell which are neglected in current IBIS model. We really not expect
> IBIS model with added IvsT info could complete replace the SPICE model in
> SSO simulation, but we do think it can greatly reduce the simulation
> accuracy gap between the SPICE model and IBIS model.
>
> About the "gate modulation effect" Arpad and Todd mentioned, I think it is
> more like a problem which can be correctly addressed by EDA tool vendor.
> Certainly in order to correctly solve this problem in IBIS, the IBIS model
> should provide enough information for the EDA tool vendor to use them.
For
> the current IBIS, the power is assumed to be perfect, so there is no
correct
> way to consider this effect in the EDA tool. With the introduction of
> BIRD95, EDA tool vendors could think how to simulate power noise due to
I/O
> switching (as a first step, the mutual impact between the I/O network and
> power network may not be able to fully considered). I think it is
> relatively easily to implement the impact of I/O noise to the power
network,
> but it is relatively hard to implement the impact of power noise to the
I/O
> network by using IBIS model. I may be wrong. There are a lot of smart
> people in the EDA industry and they may be able to figure out how to
> implement it correctly (or closer to the SPICE model).
>
> Best regards,
>
> Zhiping
>
> -----------------------------------------------------------------
> |For help or to subscribe/unsubscribe, email majordomo@eda.org
> |with the appropriate command message(s) in the body:
> |
> | help
> | subscribe ibis <optional e-mail address, if different>
> | subscribe ibis-users <optional e-mail address, if different>
> | unsubscribe ibis <optional e-mail address, if different>
> | unsubscribe ibis-users <optional e-mail address, if different>
> |
> |or email a request to ibis-request@eda.org.
> |
> |IBIS reflector archives exist under:
> |
> | http://www.eda.org/pub/ibis/email_archive/ Recent
> | http://www.eda.org/pub/ibis/users_archive/ Recent
> | http://www.eda.org/pub/ibis/email/ E-mail since 1993
-----------------------------------------------------------------
|For help or to subscribe/unsubscribe, email majordomo@eda.org
|with the appropriate command message(s) in the body:
|
| help
| subscribe ibis <optional e-mail address, if different>
| subscribe ibis-users <optional e-mail address, if different>
| unsubscribe ibis <optional e-mail address, if different>
| unsubscribe ibis-users <optional e-mail address, if different>
|
|or email a request to ibis-request@eda.org.
|
|IBIS reflector archives exist under:
|
| http://www.eda.org/pub/ibis/email_archive/ Recent
| http://www.eda.org/pub/ibis/users_archive/ Recent
| http://www.eda.org/pub/ibis/email/ E-mail since 1993
Received on Mon Jan 10 12:02:46 2005