JamesHagerman

Disassembling 1bitsy examples using radare2

Note that because radare2 uses Capstone to disassemble ARM code, there are issues with the disassembly. arm-none-eabi-objdump -d compiledbinary.elf actually does a better job in some cases. For example, msr isn't decompiled correctly...

First, you have to either strip the default ELF binaries the default Makefiles build when you run make OR you need to just compile .bin files using something like:

make binaryname.bin

wkjagt

;  ___           _        __ ___  __ ___
; / __|_ _  __ _| |_____ / /| __|/  \_  )
; \__ \ ' \/ _` | / / -_) _ \__ \ () / /
; |___/_||_\__,_|_\_\___\___/___/\__/___|

; An annotated version of the snake example from Nick Morgan's 6502 assembly tutorial
; on http://skilldrick.github.io/easy6502/ that I created as an exercise for myself
; to learn a little bit about assembly. I **think** I understood everything, but I may
; also be completely wrong :-)

FiloSottile

; /usr/local/bin/nasm -f macho 32.asm && ld -macosx_version_min 10.7.0 -o 32 32.o && ./32

global start

section .text
start:
    push    dword msg.len
    push    dword msg
    push    dword 1
    mov     eax, 4

hellerbarde

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

jboner

Latency Comparison Numbers (~2012)
----------------------------------
L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns                      14x L1 cache
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy             3,000   ns        3 us
Send 1K bytes over 1 Gbps network       10,000   ns       10 us
Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD

rakhmad

Setting Up Clojure on OS X

I spent a lot of time trying to find a pretty optimal (for me) setup for Clojure… at the same time I was trying to dive in and learn it. This is never optimal; you shouldn't be fighting the environment while trying to learn something.

I feel like I went through a lot of pain searching Google, StackOverflow, blogs, and other sites for random tidbits of information and instructions.

This is a comprehensive "what I learned and what I ended up doing" that will hopefully be of use to others and act as a journal for myself if I ever have to do it again. I want to be very step-by-step and explain what's happening (and why) at each step.

Step 1: Getting Clojure (1.3)