Here’s an excerpt:

The concert hall at the Sydney Opera House holds 2,700 people. This blog was viewed about 21,000 times in 2011. If it were a concert at Sydney Opera House, it would take about 8 sold-out performances for that many people to see it.

Click here to see the complete report.

MIPS isn’t generally considered a useful measure of performance – it’s typically quoted based on choosing the fastest (likely one of the least capable) instructions on a machine, with no regard to the capabilities of that machine.

Consider, if I built a machine that could only execute NOP, but could execute 200 million NOPs a second, it would be a 200 MIPS machine, however, if I built an entire fully feature CPU that could execute only 100 million NOPs per second (and NOP was the fastest instruction) but could also execute loads, stores, adds, multiplies etc. etc., it would be a 100 MIPS machine – however, the NOP-only machine appears (using the MIPS measure) to be twice as “good” despite being useless.

DMIPS is based on the time taken to execute a particular benchmark, something which might be considered representative of a real workload, namely Dhrystone. The DMIPS figure for a given machine is the relative speed a VAX 11/780 (a particular “1 MIPS” machine) would have to run at to complete the benchmark in the same amount of time as the machine being measured. For example, if a 100MHz CPU completes the benchmark 200 times faster than the VAX 11/780 does, then it would be considered a 200 DMIPS machine. For CPUs that can be run at various frequencies, then you’ll often see this value reported divided through by MHz, e.g. 2 DMIPS/MHz

Both are utterly useless when you want to determine whether a special device will provide enough performance to execute a given task. to be fair though, MIPS are even a little bit more useless than DMIPs.

Use a small program that represents an important part of your task and execute that one on an evaluation board. That’s the way to go.

To run Qt Linux applications, we must first start one process to act as a GUI server. Most of the Linux distributions run X11 as the default GUI server. X11 runs in the background. Once the X11 is started it takes care of framebuffer (the memory area associated with the video display) and becomes a server. The server is responsible for allocating screen regions to clients and for generating mouse and keyboard events.

When you launch a GUI application (client), the client applications communicate with the GUI server using shared memory and Unix pipes. The clients draw themselves into the Linux framebuffer and are responsible for painting their own window decorations, etc.

But in embedded such as mobile, PDA, car infotainment, etc., generally will have slower processors, less permanent storage (flash memory or hard disk), less memory, and smaller displays than desktop computers. In such case QT can come into rescue.

Unlike Qt/X11, it does not need the X Window System; instead, it implements its own window system QWS (Qt Window System), enabling significant storage and memory savings. To reduce its memory footprint even more, Qt/Embedded Linux can be recompiled to exclude unused features. If the applications and components used on a device are known in advance, they can be compiled together into a single executable that links statically against the Qt/Embedded Linux libraries.

Qt draws directly to the Linux framebuffer Make sure the /dev/fb0 device have write permissions to access the framebuffer, otherwise it may though permission denied errors.

QApplication app(argc, &argv0, QApplication::GuiServer);

If you are running only one application then simply passing -qws or else if you are planning to run multiple GUI application then passing QApplication::GuiServer to QApplication constructor is good option.

Else if there are more than one QT application to be executed at a time, then having a QT GUI server running in the background and multiple clients connecting to that server and using the framebuffer is better choice. where the server will take care of sharing the desktop between devices.

Here is a simple QT GUI server code.

#include

int main(int argc, char *argv[])
{
  // Start the qtapp thread in server mode
  QApplication app(argc, argv, QApplication::GuiServer);
  return app.exec();
}

Compile this application and execute it in background in the target board

$ ./qt_server &

Our QT GUI server is running in the background and ready to service the QT clients, So now start you QT app, may be a simple hello app to test.

All the best.

http://free-electrons.com/blog/elce-2011-videos/

Thanks to the free-electrons.com for making this available to the world.

CentOS, Debian/Ubuntu method

But by default OpenJDK based java was installed in my system.

[root@server2 sandbox]# java -version
java version “1.6.0_17″
OpenJDK Runtime Environment (IcedTea6 1.7.9) (rhel-1.36.b17.el6_0-x86_64)
OpenJDK 64-Bit Server VM (build 14.0-b16, mixed mode)

Step 1: Donwload JDK from http://www.java.com. I got JDK version 7 in rpm format.

mohamed@SilentStorm $ ls *.rpm
jdk-7-linux-x64.rpm

Step 2: Install the RPM.

[root@server2 sandbox]# rpm -i jdk-7-linux-x64.rpm
Unpacking JAR files…
rt.jar…
jsse.jar…
charsets.jar…
tools.jar…
localedata.jar…

By default Java will be installed to /usr/java/jdk1.7.0/

Step 3:  Add this new java to the alternatives configuration & Update the java alternatives

[root@server2 sandbox]# alternatives - -install /usr/bin/java java /usr/java/jdk1.7.0/bin/java 2
[root@server2 sandbox]# alternatives – -config java

There are 3 programs which provide ‘java’.

Selection Command
———————————————–
*+ 1 /usr/lib/jvm/jre-1.6.0-openjdk.x86_64/bin/java
2 /usr/lib/jvm/jre-1.5.0-gcj/bin/java
3 /usr/java/jdk1.7.0/bin/java

Enter to keep the current selection[+], or type selection number: 3

Step 4: Now verify the java version

[root@server2 sandbox]# java -version
java version “1.7.0″
Java(TM) SE Runtime Environment (build 1.7.0-b147)
Java HotSpot(TM) 64-Bit Server VM (build 21.0-b17, mixed mode)

OpenSUSE way is here

# rpm -i jdk-7-linux-i586.rpm
Unpacking JAR files…
rt.jar…
jsse.jar…
charsets.jar…
tools.jar…
localedata.jar…
plugin.jar…
javaws.jar…
deploy.jar…

# update-alternatives – -install /usr/bin/java java /usr/java/jdk1.7.0/bin/java 2
# update-alternatives – -config java

There are 3 alternatives which provide `java’.
Selection    Alternative
———————————————–
*+        1    /usr/lib/jvm/jre-1.6.0-openjdk/bin/java
2    /usr/lib/jvm/jre-1.5.0-gcj/bin/java
3    /usr/java/jdk1.7.0/bin/java
Press enter to keep the default[*], or type selection number: 3
Using ‘/usr/java/jdk1.7.0/bin/java’ to provide ‘java’.
# java -version
java version “1.7.0″

Congrats! you have made it.

Open /etc/inittab in the editor (I use vim).

su -c ‘vim -w /etc/inittab’

You will see line similar to the below on

id:5:initdefault:

You simply change the “5″ to the runlevel you desire. 
Since my machine is a server I changed it to “3″
Save the file and exit.

Unfortunately, it omits such influential languages as Lisp, ALGOL 60 and Smalltalk. But including every important language ever would make for a pretty long infographic.

http://www.rackspace.com/cloud/blog/2011/05/17/infographic-evolution-of-computer-languages/

Safe mode in Android is something equivalent to Safe mode in Widows OS. In this mode the installed application and services will not start by default. The device will be booted into default mode, so you can uninstall the bugy software that causes the issue.

Since I am using LG Optimus One P500, The instruction to enter safe mode as per the user manual is below. Refer your mobiles user manual for how to enter into safe mode.

1. Turn off your phone

2. Turn on your phone. Press and hold the menu key during Android Logo is displayed

3. Your phone will boot all the way in to main screen and dispaly “Safe mode” in lower left corner.

To turn off safe mode, simply reboot your device.

Usualy this can be due to buggy application that you have installed recently.

If your system has more than one version of Java, type the following command in a terminal window:

sudo update-alternatives –config java

Choose the version that you want to use.