Re: Free electronics simulation software

"Helmut Sennewald" <helmutsennewald@xxxxxxxxxxx> schrieb im Newsbeitrag
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"engr4fun" <engr4fun@xxxxxxxxx> schrieb im Newsbeitrag
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Helmut,

I tried to post this information previously but it doesn't seem to
have taken. My coworker tried one more circuit from the list since
then.

We can't provide the original circuits we used, but we found some on
the web called MCNC which are supposed to be SPICE benchmark
circuits. The three simulators tested were PSpice Ver 9, Micro-Cap 9,
and LTSpice 2.20k. I know PSpice is an older version but the guys who
use it love it and don't want to upgrade to the creature that Cadence
has created. Both PSpice and Micro-Cap are professional versions not
student versions. For the system we did this on, both Micro-Cap and
LTSpice were fresh installs so everything was defaulted. We set
PSpice back to its default conditions as best we could. We chose
circuits randomly from the set while ignoring the huge ones since we
can't put too much time into this. In each simulator, we just loaded
the circuit and simulated. That's all. The results were:

SQRT.CIR
PSpice - 100.98s
Micro-Cap - 99.06s
LTSpice - 207.046s

AROM.CIR
PSpice - 8.11s
Micro-Cap - 4.41s
LTSpice - 10.25s

ADD32.CIR
PSpice - 609.53s
Micro-Cap - 868.70s
LTSpice - 1917.749s

MUX8.CIR
PSpice - 15.06s
Micro-Cap - 7.52s
LTSpice - 15.25s

I must be missing some setting to change in LTSpice but this is how it
installs.

Alex


Hello Alex,

There is a default setting of trtol=7 for PSPICE and Micro-Cap.
LTspice has the more precise default setting trtol=1.
LTspice will run about two times faster if trtol is rised from 1 to 7.
If I divide your numbers by this factor, LTspice looks as fast as PSPICE
and Micro-Cap

Please add the following SPICE-line to the netlists for a comparable
result.

.options trtol=7


I tried the same netlists on my PC with LTspice.
AMD64-4000+(2.4GHz), 2GB
Benchmark files: http://www.intusoft.com/models/MCNC.zip


SQRT.sp
trtol=1 142.3sec
trtol=7 70.2sec

AROM.sp
trtol=1 4.8sec
trtol=7 2.1sec

ADD32.sp
trtol=1 1110sec
trtol=7 768sec
trtol=6 706sec
trtol=5 720sec

Hello again,

An additional cshunt-capacitance avoids numerical problems with
hyper-fast unreralistic transitions. Just think of it as a fraction of
the wiring capacitance.
trtol=7
cshunrt=1f
-> 605sec

Now we are back at about this factor 2 in speed compared to trtol=7.

Best regarsd,
Helmut


MUX8.sp
trtol=1 7.3sec
trtol=7 3.7sec


Best regards,
Helmut

PS: I don't expect it would be faster with a 2.4GHz Core-2 Duo.



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