Use of femto scaling in IBIS models

Ibisians,

I have recently found a problem in the parser which affects both
versions of the parser when parsing version 1.x IBIS models which
contain values scaled using the femto(f) prefix.

As far as I know this only affects Intel models as everyone else
uses unscaled number in engineering/scientific format.

According to the IBIS 1.1 spec, the prefix f is not
a legal prefix, pico is the smallest allowed. As the Intel model is
set as version 1.1 it is not a valid IBIS model.
Also the IBIS2.1 parser does not pick it up as it uses the IBIS v1.1
parser checker.

Illegal scale characters in the IBIS file are set to ' ' i.e. scale=1.0
without any error message.

I fiexed it by adding the character f to the known_scales array
i.e Mkmunp -> Mkmunpf
If the IBIS version in the file is set to 2.1 it will work OK
as f is recognised.

This should only affect simulated models, as measured models are
somewhat difficult to measure to that degree of accuracy.
I did once see currents of magnitude e+41 in an Intel model which I
presumed was simulated otherwise most of California would have been
blacked out!

Here is a supplementary question. Why is not having the same file
name as that in the file classified as an error rather than a warning?
Even if the file has the right name and you access it through a full
path name you get the error.

Regards

Mike

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