Introduction

SPIM and XSPIM are simulators for the MIPS Assembly Language (MAL) described Appendix B of Computer Organization & Design, by David A. Patterson and John L. Hennessy. SPIM has a command-line user interface, while XSPIM has a X-Windows based graphical user interface. SPIM and XSPIM were written by James R. Larus. There is also a PCSPIM program for the Windows platform. If you want to install any of these programs on your own machine, see SPIM: A MIPS32 Simulator.

Setting Up for Using SPIM and XSPIM

At UMD, SPIM and XSPIM are compiled to run directly on the UNIX workstations. SPIM can be run from other machines via remote login. XSPIM can be run remotely via secure login or an XWin-32 connection. If you are not familiar with UNIX, see A UNIX Reference. Also, print out these instructions so that you will have them available in case something goes wrong.

On UNIX workstations, you will often need to enter UNIX commands. These commands can be entered into an xterm window or another type of command window. Ask a lab consultant to show you how to open one of these windows.

Starting SPIM and XSPIM

To start up the xspim program, give the following command:

    xspim &
      

To start up the spim program, give the following command:

    spim
      

Assembling and Running MAL Programs with XSPIM

Each time you run a MAL program, you need to

• clear memory and registers: press the clear button and release it on "registers & memory".
• load a program named sums.s: click on the load button, enter sum.s in the dialog box, and click on "assembly" or hit the return key>
• run the program: click the run button and click on "ok" in the dialog box.

Be sure to check the status pane at the bottom of the xspim window after the load step - this is where assembly errors are reported. If you try to run a program that did not assemble correctly, you will get strange behavior.

When you are done with your xspim session,

• terminate xspim: click the quit button and click on "quit" in the dialog box.

Assembling and Running MAL Programs with SPIM

For making typescript or remote logins, you should run spim rather than xspim. spim has the same functionality as xspim, but it uses a command-line user interface. The most frequently used commands are

• clear memory and registers: enter the command reinit.
• load a program named sums.s: enter the command load "sums.s".
• run the program: enter the command run, and
• terminate spim: enter the command exit.

Using SPIM and XSPIM in Parallel with an Editor

While writing and running assembly language programs, you will often repeat an edit-clear-load-run cycle several times during a session. This is easier if you run both spim or xspim and an editor simultaneously. You can do this with xspim by starting it up with the command

    xspim &
      

and then starting up your favorite editor. The ampersand tells UNIX to run the program as a background process so that you get a new prompt. After editing, be sure to save changes before clearing, loading, and running in xspim.

You can also use spim in parallel with an editor, but you will need to open two xterm windows, starting spim in one and the editor in the other.