1. IOWA STATE UNIVERSITY
TEAM PROJECT:
PROPOSAL/REPORT
BLUEBERRY STRUDEL: THE QUEST FOR A BETTER BOARD
An analysis of the projected effectiveness of the BeagleBoard, PandaBoard, and Raspberry Pi
ENGLISH 314: TECHNICAL WRITING
SECTION ENGL 314 - 6
PROFESSOR MICHAEL SATTERWHITE
BY
SESHAPPA, ABHISHEK
SCHNIEDERS, THOMAS
SHRADER, BRYAN
AMES, IOWA
26 JULY 2012
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Letter of Transmittal
TO: Mr. Joe Holub, Advisor of LVC at VRAC
FROM: Mr. Seshappa, Abhishek; Mr. Schnieders, Thomas; Mr. Shrader, Bryan
DATE: 31 July 2012
SUBJECT: Team Project Letter of Transmittal
Enclosed is a report on three different low-power, open source hardware, single-board computers
– the BeagleBoard, the PandaBoard, and the Raspberry Pi as well as the team’s recommendation.
The recommendation is based on each respective board’s power consumption, ease of use,
functionality, size, price, and processing power in accordance with the specifications for the
Department of Defense Project -- Homunculus Camera (HomCam), carried out by the Live,
Virtual, and Constructive (LVC) training department within the Virtual Reality Applications
Center (VRAC).
Please look over this proposal. The team welcomes any feedback you may have.
Thank you for your time. You may contact any of the team members by email.
Mr. Abhishek Seshappa
Mechanical Engineering
seshappa@iastate.edu
Mr. Thomas Schnieders
Mechanical Engineering
Research Assistant -- VRAC
tms@iastate.edu
Mr. Bryan Shrader
Computer Science
Lab Consultant -- COB Labs
shrader@iastate.edu
Enclosed: Proposal for Homunculus Camera
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Table of Contents
Letter of Transmittal......................................................................................................................i
Table of Contents.........................................................................................................................ii
Abstract .......................................................................................................................................1
I. Problem....................................................................................................................................2
II. Device Attributes......................................................................................................................3
A. Preliminary Information........................................................................................................3
1. System on a Chip.............................................................................................................3
2. Single-Board Computer....................................................................................................3
B. Candidate Commonalities....................................................................................................3
1. ARM Architecture..............................................................................................................3
2. PowerVR SGX..................................................................................................................3
3. Operating Systems...........................................................................................................3
4. System on a Chip (SoC)...................................................................................................3
C. BeagleBoard.......................................................................................................................5
D. PandaBoard.........................................................................................................................7
E. Raspberry Pi........................................................................................................................9
III. Analysis................................................................................................................................10
IV. Conclusion............................................................................................................................11
V. Appendices............................................................................................................................12
Appendix A: Common Acronyms............................................................................................12
Appendix B: Glossary.............................................................................................................13
1. Processor/CPU (Central Processing Unit)......................................................................13
2. Accelerator......................................................................................................................13
3. GPU (Graphics Processing Unit)....................................................................................13
4. DSP (Digital Signal Processor).......................................................................................13
5. Single-board Computer...................................................................................................13
6. Open Source Hardware..................................................................................................13
7. SoC (System on Chip)....................................................................................................13
8. PoP (Package on Package)............................................................................................13
9. Memory...........................................................................................................................14
10. Instruction Set...............................................................................................................14
11. Clock Cycle...................................................................................................................14
12. Transistors and Binary..................................................................................................15
13. Logic Gates...................................................................................................................15
14. Pipelining......................................................................................................................15
15. SIMD (Single Instruction Multiple Data)........................................................................16
Appendix C. Common Input/Output (I/O) Ports......................................................................17
VI. Works Cited..........................................................................................................................18
VII. Other References................................................................................................................19
VIII. Image Sources...................................................................................................................22
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Abstract
The Homunculus Camera (HomCam) project, funded by the U.S. Department of Defense and
developed by the Live, Virtual, and Constructive department of the Virtual Reality Applications
Center at Iowa State University, attaches four cameras and a single-board computer to a helmet.
The assembled device records a full three-hundred-sixty-degree video stream of the wearer's
environment, saves it to an external storage device, and streams it to another location. In
upgrading the HomCam, three single-board computers (BeagleBoard, PandaBoard, Raspberry
Pi) were chosen for analysis. After analyzing the three computers on power consumption, ease
of use, functionality, size, price, and processing power, the BeagleBoard was chosen for the
upgrade.
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I. Problem
The Homunculus Camera (HomCam) project is an environment recording device funded by the
United States’ Department of Defense and developed by the Live, Virtual, and Constructive
(LVC) department of the Virtual Reality Applications Center (VRAC) at Iowa State University
(ISU). Four pinhole cameras are mounted to a helmet, and wired to a backpack containing frame
grabbers (not important to the report), a single-boarda
computer, and a power source. The
cameras collectively capture a 360° video stream of the wearer’s environment and send it to the
single-board computer in the backpack. The single-board computer stitches the individual
capture streams into one panoramic video, saves it to an external storage device, and streams it to
another location. The wiring transfers the data and power between the helmet cameras and the
backpack components. The project has been defunct for three years, but the LVC departmentb
has recently fixed it. The department is now looking to upgrade the HomCam's single-board
computer.
Based on prior research conducted by the LVC department, two new single-board computer
models, the PandaBoard and the Raspberry Pi, have been chosen for further analysis. The current
single-board computer, the BeagleBoard, will also be analyzed. These three computers will be
evaluated on the basis of processing power, A/V capture abilities, data storage and streaming
abilities, external connections, physical size and weight, and power consumption.
a. Single-Board Computer: a small computer condensed to a single board (see V.B.5)
b. LVC: Live, Virtual, and Constructive
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II. Device Attributes
A. Preliminary Information
1. System on a Chip
A System on a Chip (SoC)a
consists of several independent components that are
connected together and packaged as a single unit. SoC’s will typically contain a CPUb
, a
GPUc
, some RAMd
, and perhaps a DSP. Each of these components will have tech specs
just like a standalone component of that type. Packaging components together as an SoC
instead of separately reduces the cost and physical size of the unit, but prevents users
from swapping or replacing the individual components.
2. Single-Board Computer
A single-board computer contains all the common components of a normal computer on a
single circuit board. Single-board computers generally use an SoC for processing data;
this means that the unit that does the most work also has the smallest physical size. Most
of the board space is devoted to ports which allows the single-board computer to
communicate with other devices. A single-board computer is meant for specialized
projects such as this one rather than general computing and processing; less options are
required for a specialized project, and a single-board computer is smaller and cheaper
than a general-purpose computer.
B. Candidate Commonalities
1. ARM Architecture
ARM-Cortex is a processorb
which implements the ARM instruction set. Processors
based on ARM architecture are relatively less complex than that of traditional processors
and thus require relatively less power [1]. For this reason, ARM is analogous with “low
power consumption.” Since all three candidate devices implement some version of ARM,
they all meet the “low power” qualification.
2. PowerVR SGX
PowerVR SGX is a type of Graphics Processing Unit [15]. Both the BeagleBoard and
PandaBoard implement a version of PowerVR SGX [24][27]. This gives them both
enhanced graphics processing capabilities.
3. Operating Systems
All three devices are capable of running Linux [24][26][28]. Both the BeagleBoard and
PandaBoard are able to run Android as well [24][26].
4. System on a Chip (SoC)
a. SoC: System on Chip (see V.B.7)
b. Processor/CPU: Central Processing Unit (see V.B.1)
c. GPU: Graphics Processing Unit (see V.B.3)
d. DSP: Digital Signal Processor (see V.B.4)
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Both the BeagleBoard and the PandaBoard use an OMAP SoC, which is a specific series
of SoC's developed by Texas Instruments. An OMAP SoC generally contains an ARM-
Cortex CPU, which handles general processing, a TMS320 DSP, which processes
incoming audio and video signals, and a PowerVR SGX GPU, which processes graphical
data. The Raspberry Pi uses a Broadcom BCM2835 SoC, which uses different CPU's,
GPU's, and DSP's with lower performance.
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C. BeagleBoard
[P1]
The BeagleBoard is an open source hardwarea
single-board computer produced by Texas
Instruments (in association with Digi-Key) costing $149. The BeagleBoard processes data using
the ARM Cortex –A8, a processor core designed by ARM Holdings implementing the 7th
version instruction setb
architecturec
[1].It is a dual-issue superscalar, achieving roughly twice the
instruction executed per clock cycle. The ARM Cortex – A8 is capable of running the Linux
operating system[3], which is heavily used during software development in the LVC department
at the VRAC.
The BeagleBoard also implements the OMAP 3530, a proprietary SoC developed for portable
and mobile multimedia applications [30][8]. It is the third generation of OMAP with the OMAP
3530 being a variant of the 34x series intended for catalog distribution channels [30][31][8][10].
Each OMAP SoC contains an image, video, audio accelerator, or IVA2. Most OMAP SoC
sporting the IVA2 accelerator support 12 megapixel camera images and some support HD
imaging [8]. The OMAP 3530 has semiconductor technology at 65 nm, the ARMv7 CPU
instruction setb
, CPU running the ARM Cortex –A8 at 720 MHz, and GPU PowerVR SGX530
[30][31][10].
The PowerVR SGX530 graphics processing unit, developed by Imagination Technologies,
provides accelerated 2D and 3D rendering that supports OpenGL ES 2.0 [16].
The BeagleBoard also sports the TMS320C64x Digital Signal Processor (DSP) developed by
Texas Instruments. The TMS320C64x DSP is currently the fastest DSP on the market [13][12]
[14]. Its clock speed ranges from 300-1000 MHz [13][12][14]. The BeagleBoard uses this DSP
for accelerated video and audio recording.
The BeagleBoard houses four separate USB ports as well as a USB On-The-Go (OTG) port. It
also contains more standard I/O ports such as 2 stereo 3.5mm audio ports, composite video, S-
video, HDMI, SD card slot, and an Ethernet port. The BeagleBoard’s final I/O port is the RS-
232, which is the traditional name for a series of standards for serial binary single-ended data and
control signals connecting between a DTE and a DCE [18].
a. Open Source Hardware: The documentation is freely available to the public (see V.B.6)
b. Instruction Set: The set of instructions which a hardware device recognizes (see V.B.10)
c. See section II.A for additional information on ARM architecture.
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This single-board computer measures in at only 75x75 mm and has built in storage and memory
via PoPa
chip that includes 256 MB of NAND flash memoryb
and 256MB of RAM. Package on
Package, or PoP, is an integrated circuit packing method that combines “vertically discrete logic
and memory ball grid array (BGA) packages” [19]. Packages are installed on top of one another
which allows higher component density in devices [20]. The PoP circuit packing leads to space
savings on the motherboard which, in turns, allows the BeagleBoard to maintain its small size.
Electrically, the PoP minimizes track length between different interoperating parts which leads to
better electrical performance of devices, faster signal propagation, and reduced noise [20].
The BeagleBoard offers Joint Test Action Group (JTAG)c
standard test access port and
boundary-scan architecture. JTAG was initially developed for “testing printed circuit boards
using boundary scan” [21] and is still widely used for this application. However, JTAG is now
commonly used for IC debug ports [22]. Boundary scan itself is a method for testing
interconnects on printed circuit boards and is used as a debugging method [22].
The single-board computer also offers on-board NAND flash memory. NAND flash memoryb
implements floating-gate transistors that are connected in a way that resembles a NAND gated
,
that is, several transistorse
are connected in series [23].
a. PoP (Package-on-Package): a technique used to optimize physical space usage (see
V.B.8)
b. Flash Memory: a type memory used for long-term data storage (see V.B.9.ii)
c. JTAG: a tool used for debugging/error detection.
d. NAND Gate: a type of logic gate which is the complement of an AND Gate (see V.B.13.vi)
e. Transistors: the internal “switches” inside a computer (see V.B.12)
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D. PandaBoard
[P2]
The PandaBoard is a single-board computer (priced at ~$174) with a design layout based on
Texas Instruments’ OMAP 4430; therefore, it holds many similarities with respect to data
processing [27]. It sports two ARM Cortex-A9 processors at 1 GHz each as well as a
TMS320C64x digital signal processor at an additional 430 MHz. It also uses a 304MHz
PowerVR SG540X for enhanced 2D and 3D graphics accelerationa
[27]. These attributes make
the PandaBoard a very capable machine in terms of both audio and video processingb
.
Audio and video output on the PandaBoard are respectively handled by the means of 3.5 mm
audio and DVI ports as well as an HDMI port for high definition (both audio and video) [27].
The PandaBoard also features a memory card-reader slot, which supports SD cards up to 32
Gigabytes for optimal data storage [27]. In addition to Ethernet capabilities, the PandaBoard has
a USB On-the-Go port and two additional USB ports, adhering to the project specificationsc
[27].
The PandaBoard implements many structural policies and optimization techniques, which further
enhance its efficiency and performance. These policies/techniques are: Pipeliningd
, Speculative
Execution, Out-of-order Execution, and Superscalar architecture design [4][1]. The first three
techniques exploit the “assembly line” nature of the chip in effort to optimize hardware usage.
Under Superscalar architecture, as stated in Dr. William M. Johnson’s technical report from the
Stanford University Computer Systems Laboratory, “multiple, independent” instructions are
“executed in parallel,” effectively reducing the overall execution time [29]. The PandaBoard also
implements “Jazelle” which allows Java bytecode to be directly executed, increasing its
efficiency yet even further when Java is used [4][1]. These policies/techniques/features help to
hasten the operations of the PandaBoard.
a. Accelerator: any unit which helps to enhance processing (see V.B.2)
b. See section II.A for information regarding OMAP, ARM, TMS320C64x and PowerVR SGX.
c. See section V.C for illustrations of the Input/Output ports mentioned.
d. See section V.B.14 for a more in-depth explanation of Pipelining.
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PandaBoard includes several special features, which assist in its upkeep as well as general
testing. It is compatible with both JTAG and DMIPS, which are tools used for debugging and
performance assessment [27][4]. It also implements TrustZone security, which, according to the
ARM official website, creates a parallel, “secure” operating system in addition to the “normal”
one. This “secure world” is theoretically impervious to attack from the “normal world,” so in
event that an attacker gains full control of the “normal world,” the “secure world” is still
inaccessible [5]. The special features of the PandaBoard serve to preserve the integrity of the
machine.
PandaBoard uses the instructions sets ARMv7 and Thumb2 [4]. Thumb2 is a compact variant of
ARM (using 16 bits instead of 32). Its span of functionality is, accordingly, less than that of
ARM, requiring--in some cases--multiple instructions to simulate a single ARM instruction;
however, its shrunken nature can prove to significantly reduce the overall length of the
instruction code [1]. PandaBoard also uses advanced SIMDa
instructions (Single Instruction
Multiple Data), which allows for a single operation to be performed simultaneously on multiple
data elements [4].These instruction setsb
and policies enhance both the compatibility and
efficiency of the PandaBoard.
a. SIMD: Single Instruction Multiple Data (see V.B.15)
b. See section V.B.10 for supplementary information on instruction sets.
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E. Raspberry Pi
[P3] [P4]
The Raspberry Pi is a credit card-sized, single-board computer manufactured in the UK and sold
for $35 [28]. It is intended for general purpose computer processing on a personal scale.
The Raspberry Pi features a Broadcom BCM2835 SoC, which contains a 700 MHz
ARM1176JZF-S CPU core and a Broadcom VideoCore IV GPU/DSP. It has 256 MB of
SDRAM shared between the CPU and GPU. [17] These processors are not sufficiently powerful
on their own, but two processors can be connected to meet the necessary requirementsa
.
The Raspberry Pi accepts data through an HDMI port, an Ethernet port, a 3.5mm audio jack, and
2 USB ports. [28] For this project, only the USB ports will be used. Two single-board
computers can be connected together to accept data from all four cameras. In addition to the
previous I/O portsb
, the Raspberry Pi can also output a video feed through an RCA (composite)
connector. [28]
With physical dimensions of 85.60 × 53.98 mm (3.370 × 2.125 in) and a weight of 45 g (1.6 oz),
[28] the Raspberry Pi is very small and light. Using two computers to stream the video feed also
adds some independency, as one computer can still transmit half of the video stream if the other
computer fails. Implements pipelining, which is defined in the glossary. Supports ARM11
architecture.
a. See section II.A for additional information
b. See section V.C for an illustration of mentioned Input/Output ports.
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III. Analysis
In order to complete the Homunculus Camera project, the team requires a low power,
lightweight, single-board computer with approximately 1 GHz of video/audio processing power
(for storing and streaming), data storage capability, and multiple USB ports. Since all three
candidates are single-board computers that are lightweight and consume little energy [II.A.1,2],
the team’s focus is narrowed primarily to the respective processing, data storage, and USB
elements. Price is not viewed as an eliminating factor; however, a low price can sometimes make
other attributes become all the more appealing. The team’s duty is to analyze the data at hand,
having already in their possession (from a previous project) the model of BeagleBoard described
above, and determine if a change to either the PandaBoard or Raspberry Pi would prove
beneficial (see Table 1 on next page for an illustration of each board’s comparative attributes).
The BeagleBoard is a strong candidate. It has sufficient processing capabilities [II.B.1] as well as
four USB ports [II.B.2]. It can store data either by way of SD Card, USB flash drive, or simply
using its featured, on-board flash memory (almost like a mini, built-in hard drive). In addition,
the memory unit is detachable, so, in the event that it suffers irreparable damage, it can be
replaced individually rather than rendering the entire board unusable [II.B.4]. The BeagleBoard
would also be the cheapest option, given that one is already in the team’s possession (thus
requiring no additional cost). It is clear that the BeagleBoard dutifully fulfills all of the project
requirements.
The PandaBoard is another strong candidate. Its processing power rivals that of even the
BeagleBoard [II.C.1]. It also comes with additional built-in security features [II.C.4]. Though it
may surpass the BeagleBoard in sheer computational power, it lacks the means of on-board data
storage; however, this may not be too huge of an issue, since SD cards and USB flash drives can
provide effective and sufficient compensation [II.B.1][II.C.1][II.C.2][II.B.4]. In addition, the
PandaBoard is the most expensive of the three units, averaging around $174. It also comes
packaged with three USB ports (one less than the BeagleBoard) [II.C.2][II.B.2]. All of the above
statements and arguments serve as a testimony that the PandaBoard does indeed meet the project
requirements.
The Raspberry Pi is an extremely interesting device. It is only the size of a credit card, yet
despite its small stature, it manages to retain a decent amount of processing power, though this
power is significantly less than that of the BeagleBoard or PandaBoard [II.B.1][II.C.1][II.D.1]. It
is also, fittingly, an incredibly cheap unit, ranging from $25-$35. One of the major downfalls of
the Raspberry Pi is that it has only two USB ports, already making it a suboptimal choice by
comparison [II.D.2]. Though it is a very cool device, it would simply not be feasible--or would
be, at least, impractical--to integrate the Raspberry Pi into the HomCom project.
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Table 1: A comparative illustration of each board's attributes
IV. Conclusion
The team recommends staying with the BeagleBoard. It has already proven its effective use
fulfilling all of the project’s requirements when applied in the Haptics Lab in the LVC
department of VRAC. However, the team also firmly believes that the PandaBoard would also
make a fitting upgrade if and when the project moves on to its projected upgraded second phase
for the LVC department’s Department of Defense contract.
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V. Appendices
Appendix A: Common Acronyms
1. VRAC = Virtual Reality Applications Center
2. LVC = Live, Virtual, and Constructive
3. CPU = Central Processing Unit (i.e. Processor) [B.1]
4. GPU = Graphics Processing Unit [B.3]
5. DSP = Digital Signal Processor [B.4]
6. RAM = Random Access Memory [B.9.i]
7. I/O = Input/Output [C]
8. SoC = System on Chip [B.7]
9. PoP = Package on Package [B.8]
10. SIMD = Single Instruction Multiple Data [B.15]
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Appendix B: Glossary
1. Processor/CPU (Central Processing Unit)
The Processor/CPU is the unit of a computer/device responsible for the processing and
execution of instructions.
2. Accelerator
An “accelerator” is typically a specialized unit which effectively relieves some of the
burden placed on CPU in terms of processing. The term “accelerator” can refer to,
essentially, anything which enhances (or accelerates) a system’s ability to process data
(e.g. graphics, video, audio). GPUs and DSPs can both be considered accelerators. [B.3]
[B.4]
3. GPU (Graphics Processing Unit)
A GPU is a unit which specializes in the processing of graphics. It is typically given the
task of transforming internal graphics data into a form recognizable by the
monitor/display. In essence, it acts as the translator between the computer/device and
display unit (or I/O).
4. DSP (Digital Signal Processor)
A DSP is a unit which specializes in the processing of digital signals (e.g converting
between analog and digital signals). It is typically given the task of transforming raw data
(e.g from I/O ports) into a form which the computer/device can more easily manipulate
and understand.
5. Single-board Computer
A Single-board computer is just that--a functional computer condensed into a single
board/chip. It is a small computer complete with a processor [B.1], RAM [B.9.i], I/O
ports [C], and other necessary components.
6. Open Source Hardware
The term open source refers to any program or project, the source of which (i.e its
internal structure and means of creation) is freely accessible to the public. Open source
hardware takes this concept and applies it to hardware architecture, that is, the design and
layout of the device is well documented, and said documentation is easily accessible.
7. SoC (System on Chip)
SoC refers to the specific layout requirements of a single-board computer/device [B.5]. It
includes the type of processor(s) as well as the additional components (i.e the “system”)
on the chip/board.
8. PoP (Package on Package)
PoP is a physical space optimization technique whereby modules are strategically
mounted over top one another in effort to better utilize the occupied space on the
board/chip (see Figure 1 on next page)
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Figure 1: A visual illustration of “Package-on-Package” [P5].
9. Memory
Memory comes in many different flavors. Below are illustrated three different types of
system memory:
i. RAM (Random Access Memory)
RAM is most analogous with “short-term memory.” It is what the system
uses to, essentially, run. Due to its nature, RAM is not used for long-term
data storage. It can be likened unto “scratch paper” for the computer as it
performs its computations.
ii. Flash Memory
This is the kind of memory which is found in USB flash drives as well as
SD cards. The data is rather easily accessible and re-writable, making it
optimal for the relatively longer-term (and even not-so-long-term) data
storage needs.
iii. Instruction Memory
This is memory built into a unit for the sake of reference and is not
intended to be changed. It contains the means by which the machine is
able to decode/interpret given instructions [B.10].
10. Instruction Set
Every machine/unit/chip has a set of “instructions” which it understands. This is, in
essence, the “language” that the machine recognizes. Each of the instructions is relatively
simple in nature, featuring a primitive calculation/computation of some kind (e.g
add/subtract). When the source code for a program is compiled on a given machine, it is
essentially translated into a sequence of instructions from the machine’s respective
instruction set. Additionally, the term “Driver” refers to software with the purpose of (for
all intensive purposes) communicating between machines with different instruction sets.
A unit with a more encompassing instruction set typically has, in turn, a greater
compatibility threshold (i.e. it is likely to be compatible with a larger variety of devices).
11. Clock Cycle
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This is the unit of time measurement used internally by the machine. A computer is
essentially a complex collection of “conductive tissue” and glorified “wires”; therefore, it
follows that on any given moment in time, only one specific voltage of electricity is
capable of being transmitted through each “wire” [B.12]. Each of these moments is
referred to as a “clock cycle.” During a single clock cycle, each circuit is mapped to a
particular voltage (either ‘higher’ or ‘lower’). On each following clock cycle, this
mapping is reconfigured based on the impulses from the previous cycle (including
additional inputs). The greater the number of clock cycles per second, the greater the
number of instructions which can be executed per second (i.e. the faster the computation).
12. Transistors and Binary
A transistor is a glorified switch and is the lifeblood (well, probably more like lifeblood-
vessel) of the computing process. It simulates a basic, binary, decision problem. The
binary alphabet (‘0’ and ‘1’) is an abstraction for “computer language,” which is based on
two ranges of electric voltage flowing through its circuits (‘lower’ and ‘higher’
(relatively) which correspond respectively to ‘0’ and ‘1’). Different portions of computers
are designed to react differently to the higher voltage than they do to the lower. This
effectively allows them to, so to speak, “interpret and speak binary.” Transistors are key
to the functionality of logic gates [B.13].
13. Logic Gates
Logic gates are computational structures, implementing transistors [B.12] which perform
a primitive operation on binary inputs. The most common operations are: AND, OR,
NOT, XOR, NOR, and NAND. Each of these takes as input two binary values (with the
exception of NOT which takes one) and outputs a single binary value. Below is a brief
description of each logic gate operation (inputs are labeled as x and y). The output of
each operation is ‘0’ unless a condition is otherwise specified.
i. AND
outputs ‘1’ only if both x and y are ‘1’.
ii. OR
outputs ‘1’ if either x or y are ‘1’
iii. NOT
outputs the complement of x (i.e. ‘0’ if x is ‘1’ and ‘1’ if x is ‘0’)
iv. XOR
outputs ‘1’ if either x or y are ‘1’, but ‘0’ if both x and y are ‘1’
v. NOR
outputs ‘1’ if neither x nor y are ‘1’ (the complement of OR)
vi. NAND
outputs ‘1’ as long as x and y are not both ‘1’ (the complement of AND)
14. Pipelining
Pipelining is a method of utilizing the “assembly line” nature of a chip to begin the
processing of instructions before previous instructions have completely finished
execution. A chip is usually comprised of several modules, and the processing/execution
of an instruction is divided into several stages (normally these are: instruction fetch,
instruction decode, execution, memory query, and writeback). Each stage pertains to
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certain, independent modules and requires a clock cycle [B.11] for completion. Once an
instruction has passed the first stage, the corresponding, independent modules are
normally left to dormantly idle for the remainder of the process. Pipelining makes
intelligent use of this downtime by calling these idling modules back into action--by
preemptively initiating the process for the next instruction. This allows much of the
processing between instructions to overlap, giving the potential for drastic a increase in
performance. To illustrate this point, three instructions, which would normally require a
collective 15 clock cycles (5 clock cycles each), can theoretically be completed in only 7
(see Figure 2 below).
Figure 2: An illustration of three instructions being executed in 7 clock cycles by means of
pipelining
15. SIMD (Single Instruction Multiple Data)
This refers to the architecture policy in which an instruction is capable of performing a
single operation simultaneously on several independent, parallel portions of data.
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<http://www.raspberrypi.org/faqs>
[29] "Super-Scalar Processor Design". William M. Johnson (June 1989). Stanford University
Computer Systems Laboratory. Technical Report No. CSL-TR-89-383. Accessed
7/25/2012 <ftp://reports.stanford.edu/pub/cstr/reports/csl/tr/89/383/CSL-TR-89-383.pdf>
[30] “OMAP35x Processors Now Performance Optimized at 720MHz”. Accessed 7/15/2012
14:35 Texas Instruments. <http://www.ti.com/dsp/docs/dspcontent.tsp?
contentId=53403&DCMP=OMAP_Feb27_2008&HQS=Other+OT+omap35x>
[31] “OMAP3530 (ACTIVE) Applications Processor”. Texas Instruments. Accessed 7/15/2012
14:40. <http://www.ti.com/product/omap3530>
25. 22 Blueberry Strudel
The Quest for a Better Board
VIII. Image Sources
[P1] BeagleBoard Illustration
<http://en.wikipedia.org/wiki/File:BeagleBoard_described.jpg>
[P2] PandaBoard Illustration
<http://theallbox.com/wp-content/uploads/2010/10/PandaBoard_Setup1.png>
[P3] Raspberry Pi Blue-and-White Illustration
<http://www.raspberrypi.org/wp-content/uploads/2011/07/raspi_blue_white.png>
[P4] Raspberry Pi Illustration
<http://i.i.com.com/cnwk.1d/i/tim/2012/06/19/Raspberry_Pi_35332544_05_1.jpg>
[P5] PoP Illustration
<http://www.finetechusa.com/uploads/pics/PoP_principle.jpg>
[P6] RCA Composite and S-Video Female Connections
<http://img.tomshardware.com/us/2005/11/23/pc_interfaces_101/scart2.jpg>
[P7] RCA Composite and 3.5 mm Audio Male Connections
<https://www.mycablemart.com/store/images/products/1806_small.jpg>
[P8] HDMI and DVI Male Connections
<http://www.smelectronics.com/images2/S-HDMI-DVI-1.jpg>
[P9] HDMI Female Connection
<http://www.optimization-world.com/img/prod/hdmi_hdmi_coupler_small.jpg>
[P10] Composite Video Male Connection
<http://www.computergear.co.uk/userfiles/image/Composite.jpg>
[P11] SD Card
<http://www.photo-dictionary.com/photofiles/list/1354/1856SD_card.jpg>
[P12] USB and RS-232 Serial
<http://www.pacificgeek.com/productimages/xl/USB2RS232-2.jpg>
[P13] Ethernet
<http://c-more.automationdirect.com/images/ethernet_port.jpg>
26. Blueberry Strudel
The Quest for a Better Board
23
[P14] S-Video Male Connection
<http://pcwizkid.co.uk/images/s-video.jpg>
[P15] DVI Female Connection
<http://www.showmecables.com/images/catalog/product/DVI-Female-Female-
Adapter3.jpg>
[P16] Raspberry Pi DSI Callout
<http://i.imgur.com/k0Puu.jpg (DSI raspberry pi)>
