Add notes about alternative simulators in software README
[ci skip]
@@ -8,13 +8,17 @@ compile the program if needed before executing it.
- **run**: Execute the program in the emulator. This will pop up a
framebuffer window to display output if necessary.
-- **verirun**: Execute the program in the verilog simulator. This
+- **verirun**: Execute the program in the Verilator verilog simulator, which
+ is the default simulator that is installed by the install scripts. This
does not support a framebuffer, so you may need to make modifications to the
program to make it dump its output and stop after rendering one frame.
- **fpgarun**: Transfer it over the serial port to the FPGA board. Instructions
for setting up the FPGA are in hardware/fpga/de2-115/README.
- **debug**: Execute the program in the emulator and attach to it with the
debugger (lldb).
+- **vcsrun**: Execute program in
+ [VCS](https://www.synopsys.com/verification/simulation/vcs.html) Verilog
+ simulator if you have it installed.
For example:
