#

## extresist

Patch the extraction `.ext` files with detailed route resistance information.

### Usage:

> extresist option

> > where option may be one of the following:
> > all
> >   Extract all the nets.
> > threshold [value]
> >   With no value given, returns the current lumped resistance threshold used to determine if a network will or will not be analyzed for resistance extraction, in milliohms. The default threshold value is 10000 milliohms (10 ohms). If value is given, then set the lumped resistance threshold to value milliohms.
> > mindelay [value]
> >   With no value given, returns the current delay time threshold used to determine if a network will or will not be analyzed for resistance extraction, in picoseconds. The default mindelay value is 1ps. If value is given, then set the delay threshold to value picoseconds.
> > minres [value]
> >   With no value given, returns the current absolute resistance threshold used to prune small resistances from a network when simplifying, in milliohms. The default minres value is 1000 milliohms (1 ohm). If value is given, then set the absolute resistance threshold to value milliohms. Note that resistances smaller than value may still appear in the output netlist if the algorithm is unable to simplify the network around the resistor.
> > simplify [on|off]
> >   Turn on/off simplification of resistor nets.
> > extout [on|off]
> >   Turn on/off writing of the `.res.ext` file.
> > lumped [on|off]
> >   Turn on/off writing of updated lumped resistances.
> > silent [on|off]
> >   Turn off/on printing of nets being processed.
> > debug [on|off]
> >   Turn off/on additional diagnostic information.
> > skip mask
> >   Don't extract types indicated in the comma-separated list mask
> > ignore [netname|none]
> >   Don't extract the net named netname. The list of ignored nets is global, cumulative, and persistent; it will only be cleared when the extresist ignore none command is issued (option available from version 8.3.207).
> > include [netname|all]
> >   Extract the net named netname. When this option is called at least once, the behavior of the extraction changes to extract only the nets that have been specified by extresist include commands. The list of included nets is global, cumulative, and persistent; it will only be cleared when the extresist include all command is issued (option available from version 8.3.213).
> > box type
> >   Extract the signal under the cursor box on layer type
> > cell cellname
> >   Extract the network for the cell named cellname
> > geometry
> >   Extract network geometry and present as a collection of line elements on the layout.
> > fasthenry [freq]
> >   Extract subcircuit network geometry into a fasthenry-format `.fh` file. If freq is specified, the file will be customized for fasthenry analysis at the indicated frequency (in Hz).
> > tolerance value
> >   Deprecated! This option is no longer used by extresist.
> > help
> >   Print help information

### Summary:

> The normal flow through layout extraction into a simulation file treats routes as nonphysical entities, that is, with infinitesimal impedence through the wires. Standard extraction generates "lumped resistance" values, a single resistance per network node that, along with the node capacitance to substrate, provides an RC time constant to approximately model the delay from point to point in the network node. The lumped resistance model is inappropriate for analog (i.e., SPICE) simulation, and for digital simulation, is a poor approximation for branching networks, where the delay between endpoints is different for each pair of endpoints in the network node.

> The extresist command provides a method for generating a more detailed model of resistance, in which long network routes and branching routes are replaced with resistor devices and device networks. This is known as "full R-C extraction".

> Using extresist as a standalone command is a multi-step process. It is first necessary to run extract to get the initial netlist. After a `.ext` file has been generated, the extresist command may be run. The output is a file `.res.ext` for each cell in the hierarchy. Finally, with the option extresist on set, ext2spice will generate the final, detailed simulation file.

> Prior to magic version 8.3.597, it was also necessary to run ext2sim labels on and ext2sim to write out a `.sim` and a `.node` file before running extresist. This is no longer necessary. There is since magic version 8.3.597 an option extract do resistance that runs the resistance extraction in sequence with the regular extraction, producing both the `.ext` and `.res.ext` files. When extract do resistance is used, there is no need to run extresist as a separate command. However, extresist may be run prior to extract to set the options that affect resistance network extraction, such as extresist threshold, extresist minres, etc.

> As of magic version 8.3.653, the extresist tolerance option is deprecated and has no effect on network resistance extraction. Instead, extraction is controlled by three main options:

> extresist threshold (value in milliohms) sets a cutoff for considering a network for detailed resistance extraction based on the lumped resistance estimate (see above). For point-to-point wires, the lumped resistance is approximately equal to the actual wire resistance. For branching networks, it will generally be an over-estimate. The default threshold value is set to 10 ohms.

> extresist minres (value in milliohms) sets a cutoff for individual resistors in the detailed resistor network. Resistors below this threshold will get pruned out of the network if the simplification algorithm is able to remove them. The default minres value is set to 1 ohm.

> extresist mindelay (value in picoseconds) sets a cutoff for considering a network for detailed resistance extraction based on the end-to-end delay calculated from the lumped resistance estimate. Once the network has been extracted, the mindelay value is again evaluated against a revised calculation of the delay to determine if the extracted detailed network should be output. The default mindelay value is set to 0, indicating that only the lumped resistance threshold should be used for determining when to extract a detailed resistance network. mindelay may be used in place of threshold, or both may be used together, in which case a network is only extracted if both threshold and mindelay are exceeded.

> More details on using extresist can be found in magic Tutorial number 8.

### Implementation Notes:

> extresist is implemented as a built-in command in magic.

### See Also:

> extract
> ext2sim
> ext2spice

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Last updated: May 29, 2026 at 11:33am