ncsim performance impact of -access +R vs +RC vs +RWC?

 Hello,

+R is the least impactive of the access options,

with the next most impactive being +W (note that +W also implies +R so -access+w is the same as -access+rw)

the most impactive is +C (which also implies +RW, so -access+c is equivalent to -access+rwc).

If you absolutely need to provide access, I would suggest using an access file.  This file applies specific access options to each level of hierarchy and/or instance, thereby offering the best performance when needing to specify an access option.  An easy way to create an access file is to first run a simulation with the following command line option:

-genafile myaccess.file

The result will be a full access (rwc) simulation, but the exception is that IUS will monitor the various design elements to determine the type of access requirement each needs.  At the end of the simulation a myaccess.file will be created (btw, you can name it whatever you would like).  Then on subsequent simulations use this created access file by removing the genafile option along with any other access option and instead include the access file by adding the following to the command line:

-afile myaccess.file

btw, the command line options above are related to using irun to run the simulation.  if you are using the three step mode of simulation (ncvlog/ncelab/ncsim) let me know.

Hope that helps,

Best regards,
Mickey

There is no precise answer to this. Mickey gave a good answer already, I'd just add that with the design access turned off, the ncelab code generator adds varying amounts of performance optimisations to the design. As you demand more access (R / W /C) less of these optimisations can be applied, hence the performance drop.

Every design is different, and some may benefit more from the optimisation than others, so it's pretty much impossible to predict what performance hit you'll see with access turned on.

You'll see bigger differentials with your wave probing options I reckon...

Cheers, Steve.