Web Resources for CS3650 (Computer Systems)

Final exam: Dec. 16:
The registrar listed our final exam at:
    8:00 am - 10:00 am (online), Wednesday, Dec. 16, 2020
The final exam is open book, open notes, open online texts (ostep.org, xv6), but otherwise closed Internet.

NOTE for Fall, 2020:
This web page is for the section of Prof. Cooperman, only.
Specially for this semester, I have included a statistics web page linking to Coronavirus cases and deaths for Northeastern U., Massachusetts, the United States, and around the world.

Instructor: Gene Cooperman
Fall Semester, 2020

The office hours are as stated on the syllabus (Mon. and Thurs., 2:00 - 3:15; for Fall, 2020), and by appointment.


Course basics: Here are some immediate resources in the course for doing homework, following the readings, etc.

Course home:
The course materials will always be available either from this web page or from the course directory on the Khoury Linux computers: /course/cs3650/.
The course is based on Linux (the third of the three popular operating systems). If you do not yet have a Khoury Linux account, get one. If you are not fluent in the basics of Linux/UNIX, please go to any of the good tutorials on the Web. Personally, I like: *** this Linux tutorial *** (from M. Stonebank, U. of Surrey, England), or this *** updated one for Linux/bash *** (by C. Tothill)
Other useful tips on Linux:
  1. Productivity tip: In most settings: the four cursor keys work (for editing the current or previous commands); and the <TAB> key works (for auto-completion of filenames and commands).
  2. If you're using Apple (the second most popular operating system), the terminal window provides you with a UNIX-like environment.
  3. If you're using Windows (the most popular operating system), you can install WSL2 (Windows Subsytem for Linux, version 2). This gives you a Linux virtual machine side-by-side with Windows. If you are unsure of which Linux distribution to use, Ubuntu is a common first choice for those unfamiliar with Linux.
    (When I followed the instructions for WSL2, I got Error 0x1bc and I fixed it by downloading the MSI package listed here. I then needed to enter "Windows Features" in the search bar, and then select "Windows Hypervisor Platform", and then go back to following the Microsoft Windows instructions. Some people may also need to turn on virtualization in their BIOS. After entering BIOS, examine all options in all tabs with the letter 'v'. For me, the option was "AMD SVM".)
    (Another option is Ubuntu Multipass, which requires VirtualBox, not necessarily compatible with WSLs's use of Hyper-V. And here is a good article on installing the full Linux desktop for WSL2. However, once WSL2 grabs RAM for the desktop, it seems to not want to give it back to the rest of Windows. So, you'll want to limit RAM for WSL2 as in the guide.)
  4. But if you insist on not using WSL2, then please try putty (substitute for 'ssh') and WinSCP (substitute for 'scp').
  5. Regardless of whether you are using Linux, Apple, or Windows/WSL2 on your laptop, practice using ssh USERNAME@login.ccs.neu.edu and scp myfile.txt USERNAME@login.ccs.neu.edu: (and notice the final colon with the 'scp' command line). For help, try: man ssh and man scp.
The syllabus contains the required readings in the textbook. It's available from the link or from /course/cs3650/ (the course directory) on Khoury Linux computers. Note especially our online textbook ostep.org.
The homework subdirectory of the course directory contains all course homework, and the course directory contains all handouts.
Help directory:
The course directory includes a help directory. There are two older reviews of UNIX there. But please consider this excellent modern introduction to UNIX by M. Stonebank. (or alt, with updates to Linux/bash by C. Tothill)
Linux editors:
Please also note the directory for UNIX (Linux) editors. On Khoury Linux, try: cd /course/cs3650/unix-editors. The editor vi is a popular choice. To learn vi (estimated time: one hour), login to Khoury Linux and do:
    vi /course/cs3650/editors-unix/vitutor.vi
and follow the on-screen instructions.
MIPS assembly language:
The assembly portion of the course will be based on MIPS. Please download the MARS Simulator for use with MIPS assembly. You can find the textbook's "Green Card" online. You can find a manual for MIPS as Appendix A in the textbook or else Appendix A online. Read this, and re-read it. The latter requires your Khoury Linux password. Some other possibly useful resources from the web are this quick reference sheet and this old introduction to the MARS Simulator. The course will also heavily use the MIPS simulator.
C language:
We will briefly review the C  language (the core of Java, but including primitive types, only). For a more extensive overview of C, consider a good, free on-line C book by Mike Banahan, Declan Brady and Mark Doran.
GDB debugger, gcc compiler, etc.:
Some help files for Linux and its compilers, editors, etc. are also available. As you use Linux, please especially practice using GDB (GNU debugger). This will help when you test your homeworks under Linux. It will also reward you with more productive debugging for the rest of your computer science career.
See materials on Python, and the Python subdirectory
UNIX xv6
The original UNIX was small enough that one can read all of the code, with the right guidance. The UNIX xv6 subdirectory has an easy-to-read hyperlinked version of UNIX xv6, with about 7,000 lines of code (about 100 pages of code).
Undergraduate tutoring:
Khoury College used to offer free undergraduate upper-class tutoriing. I don't see a link to it right now (as of Sept., 2020). If someone knows more about the current status of this resource, tell me, and I'll update a link to it.

Going beyond: enrichment material:

Texts for second half of course:

MIPS Simulator for Assembly Language homework (MARS):

  1. There is a MIPS Assembly language simulator with free downloads available and online documentation. For your convenience, a copy of the simulator is at: MIPS-simulator. There is also an online video demo of the Mars simulator.
  2. To begin running the simulator, go inside the folder, and double-click on the Mars.jar icon. Alternatively, if running from the command line in Linux, type: java -jar Mars.jar If you download Mars.jar for your computer, there are also suggestions on that page for running Mars.
  3. The syntax of the assembly language is intended to be compatible with Appendix B of our textbook (also available online (requires CCIS password)).
  4. The software is distributed as a Java .jar file. It requires Java J2SE 1.5 or later. Depending on your configuration, you may be able to directly open it from the download menu.

    If you have trouble, or if you prefer to run from the command line on your own computer, the Java SDK is is also available for free download from the same download page. The instructions for running it from Windows or DOS should work equally well on Linux. The CCIS machines should already have the necessary Java SDK installed.

  5. GOTCHAS: There are several important things to watch out for.
    1. When you hit the "Assemble" menu item, any error messages about failure to assemble are in the bottom window pane, tab: "Mars Messages". Input/Output is in the bottom window pane, tab: "Run I/O"
    2. If you paste assembly code into the edit window pane, you must save that code to a file before Mars will let you assemble it.
    3. If you have selected a box with your mouse (e.g. "Value" box in the data window pane, or "Register" box), then Mars will not update the value in that box. Mars assumes you prefer to write your own value into that box, and not to allow the assembly program to use that box.
    4. If your program stops at an error, read the "Mars Messages" for the cause of the error, and then hit the "Backstep" menu item to see what caused that error. Continue hitting "Backstep" or "Singlestep" in order to identify the error.
    5. Your main routine must call the "exit" system call to terminate. It may not simply call return ("jr $ra"). Note that page B-44 of Appendix B of the text (fourth edition) has a table of "system services" (system calls). These allow you to do "exit" and also I/O.
  6. One of the nicer features of this software is a limited backstep capability (opposite of single-step) for debugging. In addition, the help menu includes a short summary of the MIPS assembly instructions. In general, I like this IDE for assembly even better than some of the IDEs that I have seen for C/C++/Java. (The one feature that I found a little unintuitive is that if you want to look at the stack (for example) instead of data, you must go to the Data Segment window pane, and use the drop-down menu at the bottom of that pane to choose "current $sp" instead of ".data".)
  7. Please note the three sample assembly programs, along with an accompanying tutorial on the same web page.
  8. I'd appreciate if if you could be on the lookout for any unusual issues, and report them promptly (along with possible workarounds), so the rest of the class can benefit. Thanks very much for your help on this.


Current Events

NEWS (from Fall, 2020):
SPECULATION ABOUT FUTURE CHIPS AND THE END OF MOORE'S LAW: (Many of these articles are from digitimes.com.)
      For context, note the Wikipedia Silicon article on the covalent radius of silicon is 0.111 nm. So, the distance between adjacent silicon atoms is the diameter (0.222 nm).
       7 nm is approximately 31.5 silicon atom diameters. 5 nm is approximately 22.5 silicon atom diameters. 3 nm is approximately 13.5 silicon atom diameters. 2 nm is approximately 9.0 silicon atom diameters.
OLD NEWS (from Spring, 2018):
Razer Phone 2 (with youtube video of two-phase vapor chamber in second half of video)

Two security bugs, recently discovered, that affect most CPUs (technical paper released on Jan. 3, 2018):

  1. Meltdown paper (potentially affects CPUs implementing out-of-order execution, a feature that has been present on many CPUs since 1995)
  2. Spectre paper (potentially read the data in the address space of a different user process)

OLDER NEWS (from Spring, 2016 and earlier):
New memory technology: Optane(3D XPoint) (Intel/Micron, from press release)
     (non-volatile memory (like Flash/SSD), but 1,000 times faster and byte-addressable; at a price between Flash and RAM ??; available now in small quantities for special applications)

OLDER NEWS from Spring, 2015:
NEWS: Talk by Yale Patt (famous researcher in Computer Architecture)
NEWS: 2015 CCIS Colloquia (research talks by invited guests to CCIS: topics including security, big data, social networks, robotics, natural language, etc.)
NEWS: Android Apps that Never Die (talk by me, Gene Cooperman, and Rohan Garg, at ACM undergrad chapter: 6 p.m., Wed., Feb. 25, 104 WVG) (pizza included)
NEWS: One VLSI fabrication facility: $6.2 billion as of 2014 (from digitimes.com): UMC to build 12-inch fab in Xiamen


What are the largest supercomputers today?


Deep Learning on NVIDIA GPUs

DeepMind Beats Human Champion at Game of Go (in 2015)

"[The deep learning algorithm of] AlphaGo doesn't actually use that much hardware in play, but we needed a lot of hardware to train it and do all the different versions and have them play each other in tournaments on the cloud. That takes quite a lot of hardware to do efficiently, so we couldn't have done it in this time frame without those resources."
NEWS: El Capitan, Frontier, and Aurora: exascale supercomputers (appearing from 2021--2023; see especially the table, lower down in this article) Coral supercomputers (appearing from 2016--2018; see especially the table, lower down in this article)

What are some popular programming languages today?

Relative Popularity of Different Languages

Benchmark Games (Which is faster, C, Java, or Python?):
(Benchmarks are notoriously variable. Be careful about how you interpret this.)

Three Newer Languages (with lessons from Scheme/Java/C/C++)

A Brief Glimpse at Some Other Assembly Languages


The GNU debugger

  A Few Simple Debugging Commands Save You Hours of Work

        INVOKING gdb:
          gdb --args  
          Example:  gdb --args ./a.out
        COMMON gdb COMMANDS:
          BREAKPOINTS:  break, continue
          STARTING:  break main, run
          WHERE AM I:  info threads, thread 1; where, frame 2; list
          PRINT:  ptype, print  (   ptype argv[0]; print argv[0]   )
          EXECUTING:  next, step, finish, continue
            (next line, step inside fnc, finish current fnc, cont. to next breakpoint)
          EXIT:  quit
          < Cursor keys work, TAB provides auto-complete >
            set follow-fork-mode child
              (after call to fork(), switch to debugging child process)
            run; TYPE ^C (ctrl-C) TO TALK TO gdb; where; print var1; etc.
          HELP:  help    e.g.: (gdb) help continue

        ADVANCED gdb:
          info function 
            IF DEBUGGING C++ CODE, you will find this useful, in order
            to discover the full GDB name of your target method.
          macro expand MACRO_FNC(ARG)
          debugging after fork:
            set detach-on-fork off
            break ...
            info inferiors
            info inferiors; inferior 2
            info threads; thread 1
            where; frame 2
            list; print myvariable
For digging deeper into GDB, try "gdb - customize it the way you want".
  NOTE: For those who like a full-screen display of the current code, try the command ^Xa (ctrl-X a) to turn full-screen mode on and off.

  NOTE: For those who like to try a reversible version of GDB, see rr-project.org (for GDB with reverse execution)



There are some good introductory materials for Python in the instructor's directory. After trying those out, here are some other Python background materials:


Virtual memory

The following note by Rob Landley is a truly excellent summary of the most important points of virtual memory as it's really used (not just the textbook theoretical synopsis):