Category Archives: Architecture

64-bit Verilog Simulator on Windows

As expected, we didn’t see nearly the performance improvement on Windows that we did on Unix. Average speed improvement was probably 3% or less on our benchmark suite. However, the 64bit simulator is still useful when you’re working on a very large design that won’t compile or run within the memory limits of 32-bit Windows (either 2GB, generally).

Improved Coexistence With Firewalls

We’ve made a change in the way we build simulations to eliminate multiple warnings that used to be generated by some firewall software (the most annoying being the built-in firewall that comes with Windows, because it  even warns about completely safe local traffic between programs on your system). We no longer create an executable called simxsim.exe each time a simulation is built that needs a new validation by the firewall (for details, see my previous post about firewalls).

Now when you build a simulation, we create a shared library called simxsim.dll (or on Unix), instead. To perform a simulation, an executable program called simxloader.exe is run, and this exe loads and runs the simxsim shared library that represents the actual simulation. Simxloader doesn’t change, so once it’s been validated once by your firewall, it doesn’t have be revalidated again every time you build a new simulation. Peace between VeriLogger and overly picky firewalls has finally been declared!

If you’ve read the previous post on how the various programs communicate in Verilogger, the only change is that where it previously read simxsim.exe, now it should read simxloader.exe (simxloader.exe is installed in the bin subdirectory of the SynaptiCAD installation directory with our other pre-built programs). The Simxsim shared library is built in the current working directory (the directory where your project file is located if you’re building with the BugHunter debugging GUI).

VeriLogger Process Communication and Firewalls

In my last post, I discussed how the VeriLogger GUI can be configured to control different simulators. Today I’ll cover the executable programs used during a typical simulation run and how they communicate with each other.

It’s particularly important to note that these programs communicate via CORBA calls using network sockets, so any firewall software on your system needs to be configured to allow this communication. Please note that this “network communication” is all strictly local to the user’s computer: no internet activity is involved. Unfortunately, most windows-based firewalls do not, in their default configurations, differentiate between inter-process and inter-computer socket communication. Most firewalls will pop-up a warning when you build and run a simulation, and this is the the best time to allow the necessary socket access. However, there are some less commonly used firewalls that are not so friendly about notifying you when it begins blocking communications.

Syncad.exe, the BugHunter debugging GUI, is the program that the user typically interacts with. Syncad.exe launches simwrapd.exe when you first build a project by pressing the yellow “Build” button. Simwrapd.exe is a “simulation wrapper” that translates commands back and forth between the debugger GUI and the simulator, so that the debugger doesn’t need to know details of which simulator is being used. Simwrapd also theoretically allows remote simulations to be run transparently by the user, but this feature is not yet enabled in current versions of BugHunter.

Simwrapd, in turn, starts a simulator executable (vlogcmd.exe or simx.exe, for example). When
simx.exe (the VeriLogger Extreme command line simulator) is run, it then runs another exe called simxgen.exe. Simxgen is the “simulation generator” that compiles these user’s code to an simulation executable file called simxsim.exe. Simxsim.exe is then run to actually compute the results of the simulation.

All the above executables except simxsim.exe are located in the SynaptiCAD/bin directory. Unlike the other exe files, simxsim.exe is not shipped with the product, but is instead created based on the user’s source files, so it is generated into the project directory where the user’s project file (.hpj) is located.
Simxsim.exe is the simulation exe that gets run when you press one of the green “Run” buttons.

The socket communication channels when using VeriLogger Extreme are as follows:
syncad.exe <->simwrapd.exe

The socket communication channels when using the older vlogcmd simulation are as follow:
syncad.exe <->simwrapd.exe

The key difference, however, between simxsim.exe and vlogcmd.exe is that a new simxsim.exe is created with every compile and it is created in the project directory, whereas there’s only one vlogcmd.exe and it’s always located in SynaptiCAD/bin (because it’s an interpreted simulator, not a compiled one).