Hello Walter, Regarding your recommendation to reject BIRD 144: 1) IBIS draws clear boundaries between (a) AMI (the dll, which is a blackbox to model equalization, CDR, etc), (b) the analog I/O Buffer itself, and (c) the package parasitics. 2) Currently, the analog I/O buffer is always defined in block (b) above i.e., in between the AMI and package parasitics blocks. 3) Also, the I/O buffer itself can be represented using the regular VT/VI tables or using a SPICE-like subckt in the [External Model] section. Based on the above IBIS boarder lines, I think that the most suitable place to point to a linear/analog I/O buffer that is represented using S-parameter data (in a Touchstone file) is from the [External Model] section. Unlike BIRD 122, both BIRDs 116 and 144 conform with the above IBIS hierarchy. BIRD 116 suggests referencing a Touchstone file from within an ISS SPICE subckt wrapper (which is OK). While BIRD 144 augments BIRD 116 by allowing the user to DIRECTLY reference the Touchstone file (i.e., without the need to wrap it inside a SPICE-like subckt) from either an [External Model] or an [External Circuit]. Referencing the Touchstone from the [External Model]/[External Circuit] sections allows the user to use a linear/analog I/O buffer represented using S-parameter data WITH/WITHOUT the AMI block (i.e., in a general manner). Hence, it does not limit the usage of Touchstone files with the existence of the AMI block in the IBIS file. So, our approach is more general and allows the user to use a Touchstone S-parameter file: - From the right IBIS block - Independently from the AMI block - With/Without the AMI and package parasitics blocks - To represent a linear I/O buffer when referenced from an [External Model] section - To represent other passive blocks (e.g., RDL, ODT) when referenced from an [External Circuit] section In addition, like BIRD 122, BIRD 144 proposes the idea to allow the user to specify various Touchstone S-parameter files (that represent many user defined corners other than the typical min/max/typ corners). The effort to specify those corners is comparable in both BIRDs. However, BIRD 122 suggests doing that in the AMI configuration file, which: 1) limits the usage of the Touchstone files to the existence of the AMI block, 2) adds extra baggage to the AMI configuration file as that file is supposed to be used to define the parameters to the AMI block (the dll block). Conversely, BIRD 144 proposes to add the user defined corners (to reference many Touchstone files) in the right IBIS blocks (i.e., [External Model] and [External Circuit] sections), which again will allow the usage of those files in a general fashion with/without the AMI block. Best regards, Feras Al-Hawari Cadence Design Systems Chelmsford, MA