Raspberry PI 3 is here!

Some days ago the Raspberry PI 3 arrived home as I had ordered one when I heard of its launch. It's certainly a faster PI than the PI 2 due to the ARM Cortex-A53 cores. More or less the +50% performance ratio is true, depending on the application of course. There are some other additions as well like WiFi and bluetooth.

The Raspberry PI 3

A closer look of the PI 3

As usual, I am providing some nbench execution results. These are consistent with the +50% performance claim. For those interested I had published nbench results on the PI 2 in the past.

BYTEmark* Native Mode Benchmark ver. 2 (10/95)
Index-split by Andrew D. Balsa (11/97)
Linux/Unix* port by Uwe F. Mayer (12/96,11/97)

TEST                : Iterations/sec.  : Old Index   : New Index
                    :                  : Pentium 90* : AMD K6/233*
--------------------:------------------:-------------:------------
NUMERIC SORT        :          654.04  :      16.77  :       5.51
STRING SORT         :          72.459  :      32.38  :       5.01
BITFIELD            :      1.9972e+08  :      34.26  :       7.16
FP EMULATION        :          134.28  :      64.44  :      14.87
FOURIER             :          6677.3  :       7.59  :       4.27
ASSIGNMENT          :          10.381  :      39.50  :      10.25
IDEA                :          2740.7  :      41.92  :      12.45
HUFFMAN             :          1008.9  :      27.98  :       8.93
NEURAL NET          :          9.8057  :      15.75  :       6.63
LU DECOMPOSITION    :          365.38  :      18.93  :      13.67
==========================ORIGINAL BYTEMARK RESULTS==========================
INTEGER INDEX       : 34.272
FLOATING-POINT INDEX: 13.131
Baseline (MSDOS*)   : Pentium* 90, 256 KB L2-cache, Watcom* compiler 10.0
==============================LINUX DATA BELOW===============================
CPU                 : 4 CPU ARMv7 Processor rev 4 (v7l)
L2 Cache            :
OS                  : Linux 4.1.18-v7+
C compiler          : gcc-4.9
libc                : libc-2.19.so
MEMORY INDEX        : 7.162
INTEGER INDEX       : 9.769
FLOATING-POINT INDEX: 7.283
Baseline (LINUX)    : AMD K6/233*, 512 KB L2-cache, gcc 2.7.2.3, libc-5.4.38
* Trademarks are property of their respective holder.

As I crossed some reports on temperature issues of PI 3 I wanted to execute some experiments on power consumption of the PI 3. I used a power meter on which I plugged the power supply unit feeding the PI. I run a few experiments and I got the following power consumption ratings:

PI running state	Power consumption
Idle	1.4W
Single threaded benchmark	2.2W
Multithreaded benchmark	4.0W
After running "poweroff"	0.5W

So, for my case it doesn't seem consume to much power. However, a comparison with the PI 2 should be performed in order to have a better picture.

OpenCL on the Raspberry PI 2

OpenCL can be enabled on the Raspberry PI 2! However, you'll be disappointed to know that I'm referring to the utilization of its CPU, not GPU. Nevertheless, running OpenCL on the PI could be useful for development and experimentation on an embedded platform.

You'll need the POCL implementation (Portable OpenCL) which relies on the LLVM. I used the just released v0.12 of POCL and the Raspbian Jessie supplied LLVM v.3.5.

After compiling and installing POCL with the natural procedure (you might need to install some libraries from the raspbian repositories, e.g. libhwloc-dev, libclang-dev or mesa-common-dev) you'll be able to compile OpenCL programs on the PI. I tested the clpeak benchmark program but the compute results were rather poor:

Platform: Portable Computing Language
Device: pthread
Driver version : 0.12-pre (Linux ARM)
Compute units : 4
Clock frequency : 900 MHz

Global memory bandwidth (GBPS)
float : 0.85
float2 : 0.87
float4 : 0.76
float8 : 0.75
float16 : 0.81

Single-precision compute (GFLOPS)
float : 0.03
float2 : 0.03
float4 : 0.03
float8 : 0.03
float16 : 0.03

Transfer bandwidth (GBPS)
enqueueWriteBuffer : 0.79
enqueueReadBuffer : 0.69
enqueueMapBuffer(for read) : 12427.57
memcpy from mapped ptr : 0.69
enqueueUnmap(after write) : 18970.70
memcpy to mapped ptr : 0.70

Kernel launch latency : 190270.91 us

In addition, the integer benchmark could not be executed for some reason. However, memory bandwidth result was decent and using a personal benchmark tool I could measure more than 1.4GB/sec memory bandwidth which is really nice for a PI!

Raspberry Pi 2 is here!

Well, it's here! Raspberry PI 2 looks very similar to it's predecessor, the Raspberry PI B+, except of two things. The rather old ARM11 core is upgraded to not one but four Cortex-A7 cores (900MHz). The Cortex-A7 is an upgrade by itself as benchmarks has shown that it is 1.5-3 times faster than the old CPU core. Four CPU cores do a decent upgrade for the same power envelope and the same price ($35). And this is not all of the changes. The new PI features double the amount of RAM which now reaches to 1GB.

To summarize it is a great upgrade of the old PI. I would say that it is the most affordable 4 core computer for applying parallel programming paradigms, e.g. OpenMP.

One can compare these nbench output to the original Raspberry PI nbench results. Keep in your mind that nbench is a single threaded benchmark.

BYTEmark* Native Mode Benchmark ver. 2 (10/95)
Index-split by Andrew D. Balsa (11/97)
Linux/Unix* port by Uwe F. Mayer (12/96,11/97)

TEST                : Iterations/sec.  : Old Index   : New Index
                    :                  : Pentium 90* : AMD K6/233*
--------------------:------------------:-------------:------------
NUMERIC SORT        :           453.9  :      11.64  :       3.82
STRING SORT         :          36.298  :      16.22  :       2.51
BITFIELD            :      1.1028e+08  :      18.92  :       3.95
FP EMULATION        :          82.381  :      39.53  :       9.12
FOURIER             :          4877.8  :       5.55  :       3.12
ASSIGNMENT          :          7.1713  :      27.29  :       7.08
IDEA                :          1364.7  :      20.87  :       6.20
HUFFMAN             :           663.8  :      18.41  :       5.88
NEURAL NET          :          5.7769  :       9.28  :       3.90
LU DECOMPOSITION    :          224.96  :      11.65  :       8.42
==========================ORIGINAL BYTEMARK RESULTS==========================
INTEGER INDEX       : 20.419
FLOATING-POINT INDEX: 8.434
Baseline (MSDOS*)   : Pentium* 90, 256 KB L2-cache, Watcom* compiler 10.0
==============================LINUX DATA BELOW===============================
CPU                 : 4 CPU ARMv7 Processor rev 5 (v7l)
L2 Cache            : 
OS                  : Linux 3.18.5-v7+
C compiler          : gcc-4.7
libc                : /lib/arm-linux-gnueabihf/libgcc_s.so.1
MEMORY INDEX        : 4.125
INTEGER INDEX       : 5.970
FLOATING-POINT INDEX: 4.678
Baseline (LINUX)    : AMD K6/233*, 512 KB L2-cache, gcc 2.7.2.3, libc-5.4.38
* Trademarks are property of their respective holder.

FUSE emulator on CRT TV screen

The FUSE emulator looks more realistic when run on a CRT TV screen. That's because the original ZX-Spectrum featured a TV tuner in order to use an ordinary TV as a monitor. Here I use a Raspberry PI to run the emulator and it runs really well!

nbench on small linux devices

One of the benchmark programs that I find most convenient to use is nbench. The reason is that it's applicable on almost every device that can execute plain C code. This means that it can run on a desktop computer as well as on a smartphone (nbench is freely available on Google Play) or a flashed router with a custom firmware (e.g. DD-Wrt with optware).

Here are three devices that I have tried it on:

Raspberry PI

ASUS RT-N16

Linksys NSLU2 

RaspPI and NSLU2 are ARM based where the RT-N16 is MIPS based.

Here you can see the results running it on a Raspberry PI (Raspbian OS):

BYTEmark* Native Mode Benchmark ver. 2 (10/95)
Index-split by Andrew D. Balsa (11/97)
Linux/Unix* port by Uwe F. Mayer (12/96,11/97)

TEST                : Iterations/sec.  : Old Index   : New Index
                    :                  : Pentium 90* : AMD K6/233*
--------------------:------------------:-------------:------------
NUMERIC SORT        :          221.64  :       5.68  :       1.87
STRING SORT         :          31.709  :      14.17  :       2.19
BITFIELD            :      8.4099e+07  :      14.43  :       3.01
FP EMULATION        :          46.363  :      22.25  :       5.13
FOURIER             :          2372.8  :       2.70  :       1.52
ASSIGNMENT          :          2.4781  :       9.43  :       2.45
IDEA                :           696.1  :      10.65  :       3.16
HUFFMAN             :          424.38  :      11.77  :       3.76
NEURAL NET          :          3.0098  :       4.83  :       2.03
LU DECOMPOSITION    :           78.72  :       4.08  :       2.94
==========================ORIGINAL BYTEMARK RESULTS==========================
INTEGER INDEX       : 11.729
FLOATING-POINT INDEX: 3.761
Baseline (MSDOS*)   : Pentium* 90, 256 KB L2-cache, Watcom* compiler 10.0
==============================LINUX DATA BELOW===============================
CPU                 :
L2 Cache            :
OS                  : Linux 3.2.27+
C compiler          : gcc-4.7
libc                : /lib/arm-linux-gnueabihf/libgcc_s.so.1
MEMORY INDEX        : 2.528
INTEGER INDEX       : 3.266
FLOATING-POINT INDEX: 2.086
Baseline (LINUX)    : AMD K6/233*, 512 KB L2-cache, gcc 2.7.2.3, libc-5.4.38
* Trademarks are property of their respective holder.

Here running it on Linksys nslu2 fileserver (flashed with SlugOS):

BYTEmark* Native Mode Benchmark ver. 2 (10/95)
Index-split by Andrew D. Balsa (11/97)
Linux/Unix* port by Uwe F. Mayer (12/96,11/97)

TEST                : Iterations/sec.  : Old Index   : New Index
                    :                  : Pentium 90* : AMD K6/233*
--------------------:------------------:-------------:------------
NUMERIC SORT        :          74.271  :       1.90  :       0.63
STRING SORT         :          6.9679  :       3.11  :       0.48
BITFIELD            :      1.8159e+07  :       3.11  :       0.65
FP EMULATION        :          17.645  :       8.47  :       1.95
FOURIER             :          75.723  :       0.09  :       0.05
ASSIGNMENT          :         0.96228  :       3.66  :       0.95
IDEA                :          176.19  :       2.69  :       0.80
HUFFMAN             :          104.82  :       2.91  :       0.93
NEURAL NET          :         0.10509  :       0.17  :       0.07
LU DECOMPOSITION    :          3.3757  :       0.17  :       0.13
==========================ORIGINAL BYTEMARK RESULTS==========================
INTEGER INDEX       : 3.324
FLOATING-POINT INDEX: 0.136
Baseline (MSDOS*)   : Pentium* 90, 256 KB L2-cache, Watcom* compiler 10.0
==============================LINUX DATA BELOW===============================
CPU                 :
L2 Cache            :
OS                  : Linux 2.6.27.8
C compiler          : gcc version 4.2.4
libc                :
MEMORY INDEX        : 0.668
INTEGER INDEX       : 0.976
FLOATING-POINT INDEX: 0.076
Baseline (LINUX)    : AMD K6/233*, 512 KB L2-cache, gcc 2.7.2.3, libc-5.4.38
* Trademarks are property of their respective holder.

And finally here running it on a Asus RT-N16 router (flashed with DD-Wrt with optware):

BYTEmark* Native Mode Benchmark ver. 2 (10/95)
Index-split by Andrew D. Balsa (11/97)
Linux/Unix* port by Uwe F. Mayer (12/96,11/97)

TEST                : Iterations/sec.  : Old Index   : New Index
                    :                  : Pentium 90* : AMD K6/233*
--------------------:------------------:-------------:------------
NUMERIC SORT        :           160.6  :       4.12  :       1.35
STRING SORT         :          3.7864  :       1.69  :       0.26
BITFIELD            :      6.3597e+07  :      10.91  :       2.28
FP EMULATION        :            28.6  :      13.72  :       3.17
FOURIER             :          19.904  :       0.02  :       0.01
ASSIGNMENT          :           1.753  :       6.67  :       1.73
IDEA                :          670.35  :      10.25  :       3.04
HUFFMAN             :          40.453  :       1.12  :       0.36
NEURAL NET          :        0.015345  :       0.02  :       0.01
LU DECOMPOSITION    :         0.43656  :       0.02  :       0.02
==========================ORIGINAL BYTEMARK RESULTS==========================
INTEGER INDEX       : 5.017
FLOATING-POINT INDEX: 0.023
Baseline (MSDOS*)   : Pentium* 90, 256 KB L2-cache, Watcom* compiler 10.0
==============================LINUX DATA BELOW===============================
CPU                 :
L2 Cache            :
OS                  : Linux 2.6.24.111
C compiler          : gcc version 4.1.1
libc                : ld-uClibc-0.9.28.so
MEMORY INDEX        : 1.011
INTEGER INDEX       : 1.470
FLOATING-POINT INDEX: 0.013
Baseline (LINUX)    : AMD K6/233*, 512 KB L2-cache, gcc 2.7.2.3, libc-5.4.38
* Trademarks are property of their respective holder.

It should be noted that the latter two devices do not feature a floating point unit and thus the performance on floating point intensive is extremely low.

One of the drawbacks of nbench application is that it is written as a single threaded application so it cannot exploit the extra cores of a multicore CPU. One of my future hobby projects could be porting nbench program to OpenMP or even OpenCL in order to exploit the full capabilities of a contemporary CPU or even a GPU. It would be fun of comparing a Raspberry PI with a GTX580 on nbench!

Raspberry PI as a home server

Now, this is my very first post.
Here is my new low energy server known as the Raspberry PI. Here it serves web pages via lighttpd and VOIP telephony via asterisk. It's definitely a low power server so one does not have to mind turning it on and off in order to save energy.

It's also very cheap (~35$) and quite popular.