Subject: BIG BIRD COMMENTS

From: [email-masked] ( Bob Ross)
Date: Tue, 22 Mar 94 22:59:24 PST

To IBIS Committee and Eric:

First, you did an impressive job, Eric, in presenting and packaging Bird10.
Most of the considerations here already have some resolution within the
proposal, but they are still items for comment and possible refinement.

(1) The .pkg file is structured very much like the .ibs file.  The header and
clarification sections are identical.  One difference is that .ibs requires
an [End] at the end of the file, but .pkg does not.  For parallelism [End]
could be required even though each [Define Package Model] section contains
an [End Model Data] statement.  So the question is, for parallelism,
should [End] be required?  This is more a format style question than one
of required functionality.  I am happy with the proposal as is.

(2) Should the package model be required to reside in a separate file .pkg? 
The structure presented from [Define Package Model] through [End Model Data]
appear to be a self contained, complete grouping which would fit very
well within the same .ibs file as the component or components referencing
it.  The parser commands for .pkg would be the same for the .ibs file.  Also,
some components may be supplied with special, one of a kind packages.  The 
search order could be to look first within the .ibs file and then to other
..pkg files.  This may be an unnecessary complication beyond what is
needed, so I can accept the proposal as is.

(3) One concern I have is that the proposed .pkg formats allow PGA 
alphanumeric nomenclature "A1 ..  AA1 .. BB1 ..".  The existing .ibs files
allow such nomenclature.  Can [Row] numbers include alphanumeric arguments in
in addition to numerical arguments?  The column ordering would have to follow
the same order as the rows.  While not stated, this could be an additional
requirement for numerical entries as well.  In the Sparce Matrix format
both the [Row] and Index entries could name actual PGA pins.

(4) "Banded Matrix" should be "Banded_Matrix".  Similarly for "Full Matrix"
and "Sparce Matrix".  Only keywords within square brackets "[" and "]" 
allow spaces.

(5) Are the same set of units as in the .ibs file allowed in the .pkg file?
I assume so and that all of the relevant format conventions in .ibs apply
to .pkg.

Finally, Eric, you have presented documentation showing conclusively that
BIG BIRD really is larger than IBIS.  That by itself deserves a 10! 

Bob Ross, 
Interconnectix, Inc.

---

From: [email-masked]
Date: Thu, 24 Mar 94 22:14:52 -0500

Bob,

  Thanks for taking the time to read it!

  With regard to the several good points you brought up:

  1)  [End] keyword at end of file?

      Oops!  I'll put that in rev 10.1 of the BIRD.

  2)  Separate .PKG file?

      It seemed to me from voice discussions in the Forum that several
      people wanted a separate file for the package, perhaps to minimize
      the impact on the parser.  But since the package models won't 
      appear until Version 2.0 comes out, and since the parser will change
      a lot then anyway, I'd be happy to see this data encapsulated in
      the .IBS file.  One problem is that, if a tool doesn't do a detailed
      package analysis and only wants the data from the [Pin] section, it'll
      have to wade through tons o' package data to find what it wants, thus
      slowing it down.

      Comments, anyone else?

  3)  PGA alphanumeric pin names?

      Frankly, I didn't realize one could use names like "AA1" for pins.
      All of the models we have on vhdl.org are from Intel, and those 
      guys always seem to use "1", "2", "3", ..., even for big, nasty
      208-pin components.  

      I admit that, on reading the 1.1 spec, I don't see that alphanumeric
      names are prohibited.  Is this an oversight, or is it an intentional
      feature of the language?

      The only problem I see with alphanumerics is how to make it clear
      what the "ordering" of the pin identifiers is.  Remember that to
      exploit symmetry you need to know which matrix index is "bigger"
      so that you can decide whether an entry is in the upper or lower 
      half. I suppose that we could let the ordering be the same as the
      order in which the names are given in the [Pin] section of the .IBS
      file.

      Before I rewrite the BIRD, I'd like clarification from others on
      whether the alphanumerics are truly kosher or not.  

      Again, anyone care to comment?

  4)  "Banded Matrix" -> Banded_Matrix

      OK!  That would make life easier. I'll put it in rev 10.1.

  5)  Are metric suffixes allowed?

      Yes.  I'll make it explicit in rev 10.1.

--Eric