AMD SimNow

From coreboot
Jump to navigation Jump to search

The wiki is being retired!

Documentation is now handled by the same processes we use for code: Add something to the Documentation/ directory in the coreboot repo, and it will be rendered to Contributions welcome!

These are the steps I use to download, install, and use the AMD SimNow simulator. You may not want to do exactly what I did, but it should get you started. There is PDF documentation that you can download on the same page as the simulator.

Download SimNow

  1. Download SimNow from AMD's website
  2. Untar the .tar.gz file you download in a convenient place (You'll now have a directory called
  3. Follow the instructions from the help section "Setting up Linux" for the Simulator
    1. To get enough "mmap"able virtual address space, make sure you have a /etc/sysctl.conf file and that it contains the following line:
 vm.max_map_count = 1048576 

Run SimNow

  1. Run ./simnow from the simnow-linux64-4.5.xpub directory
  2. Inside the SimNow Main Window do File->Open BSD, browse to the simnow-linux64-4.5.xpub/bsds directory and load either cheetah_1p.bsd or cheetah_1pjh.bsd (jh is dual-core)
Now you have a single Opteron socket motherboard with:
AMD-8132 PCI-X controller, 
AMD-8111 I/O hub, 
and Winbond W83627HF SuperIO.
  1. Copy your coreboot ROM image to simnow-linux64-4.5.xpub/Images for convenience.
  2. Open the SimNow Device Window (View->Show Devices)
  3. Double click on Memory Device #5 (Your BIOS chip)
  4. Click on the Memory Configuration Tab, and change the Base Address, Size, and File (I use Base Address = fff00000 and Size = 32 because I use a 1 MB image)
  5. Click OK to save your changes
  6. Go to the main simulator window and hit Run Simulation (Play button)

Serial Port Configuration

In order to see the console output, go to the terminal you are running ./simnow in. Hit enter. You'll see a simnow> prompt.

  1. Type serial.SetCommPort pipe and hit enter.
  2. Type serial.GetCommPort and hit enter.

On my machine this returns path (/home/myles/.simnow/com1), mode (PIPE)

Open a new terminal and type cat /home/myles/.simnow/com1/simnow_out If you need to send input to the serial port, echo to /home/myles/.simnow/com1/simnow_in

Using the snserial tool

Alternatively, you can use a tool called 'snserial' to interact with the serial ports. snserial will combine the input and output, and provide access to the combined stream through either a psuedo tty, or a telenet port.

  1. Download the snserial tool from
  2. Extract it: tar -zxvf snserial-1.0.tar.gz
  3. Build it: cd snserial/; make

Before running the tool, make sure that you have enabled the serial pipes as detailed above.

To enable serial through a pseudo TTY, start your simulation and type ./snserial comX in another Linux terminal window (where X is 1 or 2). The program will respond with:

SimNow Serial pipe Muxer

Connection established.
Type 'target remote /dev/pts/2' in GDB to connect.
(Press CTRL-C to exit)

You can now connect your serial application (minicom, or GDB for debugging) to the specified pseudo-tty.

To enable serial interaction through telnet, start the simulation and type ./snserial -t comX. The program will respond with:

SimNow Serial pipe Muxer

COM 1: Listening on port 9000
(Press CTRL-C to exit)

You can now connect to the serial stream by typing 'telnet localhost 9000' in a Linux terminal window.

Note: It is a quirk of SimNow that the pipes are not created until the simulation for the BSD is started for the first time. Make sure you start the simulation before running snserial, otherwise you will see this: Couldn't stat /home/<user>/.simnow/com1/simnow_out: No such file or directory. The best course of action is to start the simulation quickly, attach the snserial program, and then restart the simulation to see the early serial output.

Add disks

  1. Hit the Stop Simulation button if the simulation is running
    1. File->Set IDE Primary Master Image
      1. Browse to your hard drive (.HDD) image
    2. File->Set IDE Secondary Master Image
      1. Browse to a CD (.ISO) image
  2. Hit Run Simulation again

You should get output from the serial port scrolling in one terminal, and be able to watch the VGA output in the main window.

If you used buildrom to get a BIOS image with coreboot + LAB, you'll end up at a linux prompt where you can mount the disks, etc.

Creative Commons License
Creative Commons Attribution iconCreative Commons Share Alike icon
This file is licensed under the Creative Commons Attribution ShareAlike 3.0 License.
In short: you are free to share and make derivative works of the file under the conditions that you appropriately attribute it, and that you distribute it only under a license identical to this one.