Chapter 1: Introducing Computer Architecture

Exercise 1

Using your favorite programming language, develop a simulation of a single-digit decimal adder that operates in the same manner as in Babbage’s Analytical Engine. First, prompt the user for two digits in the range 0-9: the addend and the accumulator. Display the addend, the accumulator, and the carry, which is initially zero. Perform a series of cycles as follows:

1. If the addend is zero, display the values of the addend, accumulator, and carry and terminate the program
2. Decrement the addend by one and increment the accumulator by one
3. If the accumulator incremented from nine to zero, increment the carry
4. Go back to step 1

Test your code with these sums: 0+0, 0+1, 1+0, 1+2, 5+5, 9+1, and 9+9.

Answer

The Ex__1_single_digit_adder.py Python file contains the adder code:

#!/usr/bin/env python
"""Ex__1_single_digit_adder.py: Answer to Ch 1 Ex 1."""...

Chapter 2: Digital Logic

Exercise 1

Rearrange the circuit in Figure 2.5 to convert the AND gate to a NAND gate. Hint: there is no need to add or remove components.

Answer

Relocate the R2 resistor and the output signal connection point as follows:

Figure 1: NAND gate circuit

Exercise 2

Create a circuit implementation of an OR gate by modifying the circuit in Figure 2.5. Wires, transistors, and resistors can be added as needed.

Answer

The OR gate circuit is as follows:

Figure 2: OR gate circuit

Exercise 3

Search the internet for free VHDL development software suites that include a simulator. Get one of these suites, set it up, and build any simple demo projects that come with the suite to ensure it is working properly.

Answer

Some freely available VHDL development suites are as follows:

1. Xilinx Vivado Design Suite is available at https://www.xilinx.com/support/download.html.
2. Intel® Quartus® Prime...

Chapter 3: Processor Elements

Exercise 1

Consider the addition of two signed 8-bit numbers (that is, numbers in the range -128 to +127) where one operand is positive and the other is negative. Is there any pair of 8-bit numbers of different signs that, when added together, will exceed the range -128 to +127? This would constitute a signed overflow. Note: we’re only looking at addition here because, as we’ve seen, subtraction in the 6502 architecture is the same as addition with the right operand’s bits inverted.

Answer

The range of the positive (or non-negative) numbers is 0 to 127. The range of negative numbers is -128 to -1. It is only necessary to consider the extremes of each of these ranges to cover all possibilities:

Sum	Result
0 + -128	-128
...

Chapter 4: Computer System Components

Exercise 1

Create a circuit implementation of a NAND gate using two CMOS transistor pairs. Unlike NPN transistor gate circuits, no resistors are required for this circuit.

Answer

The diagram for this circuit is as follows:

Figure 3: NAND gate circuit

Exercise 2

A 16-gigabit DRAM integrated circuit has two bank group selection inputs, two bank selection inputs, and 17 row address inputs. How many bits are in each row of a bank in this device?

Answer

The DRAM circuit contains 16 gigabits = 16 × 2³⁰ bits.

The number of address bits is 2 bank group bits + 2 bank bits + 17 row address bits = 21 bits.

The row dimension of each bank is therefore (16 × 2³⁰) ÷ 2²¹ = 8,192 bits.

Chapter 5: Hardware-Software Interface

Exercise 1

Restart your computer and enter the BIOS or UEFI settings. Examine each of the menus available in this environment. Does your computer have a BIOS or does it use UEFI? Does your motherboard support overclocking? When you are finished, be sure to select the option to quit without saving changes unless you are absolutely certain you want to make changes.

Answer

In Windows, you can enter the BIOS/UEFI settings by changing the startup options while Windows is running. To access these settings, perform the following steps:

1. In the Windows search box, type startup and select Change advanced startup options.
2. Select the Restart now button under Advanced startup.
3. When prompted to Choose an option, select Troubleshoot.
4. On the Troubleshoot screen, select Advanced options.
5. On the Advanced options screen, select UEFI Firmware Settings.
6. On the UEFI Firmware Settings screen, click the Restart button...

Chapter 6: Specialized Computing Domains

Exercise 1

Rate monotonic scheduling (RMS) is an algorithm for assigning thread priorities in preemptive, hard, real-time applications in which threads execute periodically. RMS assigns the highest priority to the thread with the shortest execution period, the next-highest priority to the thread with the next-shortest execution period, and so on. An RMS system is schedulable, meaning all tasks are guaranteed to meet their deadlines (assuming no inter-thread interactions or other activities such as interrupts, resulting in processing delays) if the following condition is met:

This formula represents the maximum fraction of available processing time that can be consumed by n threads. In this formula, C_i is the maximum execution time required for thread i, and T_i is the execution period of thread i.

Is the following system composed of three threads schedulable?

...

Thread

Chapter 7: Processor and Memory Architectures

Exercise 1

A 16-bit embedded processor has separate memory regions for code and data. Code is stored in flash memory and modifiable data is stored in RAM. Some data values, such as constants and initial values for RAM data items, are stored in the same flash memory region as the program instructions. RAM and ROM reside in the same address space. Which of the processor architectures discussed in Chapter 7, Processor and Memory Architectures, best describes this processor?

Answer

Because the code and data are located in the same address space, this is a von Neumann architecture.

The fact that the code and some data items are stored in ROM and other data items reside in RAM is not relevant to determining the architecture category.

Exercise 2

The processor described in Exercise 1 has memory security features that prevent executed code from modifying program instruction memory. The processor uses physical addresses to...

Chapter 8: Performance-Enhancing Techniques

Exercise 1

Consider a direct-mapped L1-I cache of 32 KB. Each cache line consists of 64 bytes and the system address space is 4 GB. How many bits are in the cache tag? Which bit numbers (bit 0 is the least significant bit) are they within the address word?

Answer

The cache contains 32,768 bytes with 64 bytes in each line. There are 32,768 ÷ 64 = 512 sets in the cache. 512 = 2⁹. The set number is thus 9 bits in length.

Each cache line contains 64 (2⁶) bytes, which means the lower 6 bits of each address represent the byte offset within the cache line.

A 4 GB address space requires 32-bit addresses. Subtracting the 9 bits in the set number and the 6 bits in the byte offset from the 32-bit address results in 32 – (9 + 6) = 17 bits in the cache tag.

The cache tag lies in the 17 most significant bits of the address, so the range of these bits within a 32-bit address runs from bit 15 to bit 31.

Exercise 2...

Chapter 9: Specialized Processor Extensions

Exercise 1

Using a programming language that allows access to the byte representation of floating-point data types (such as C or C++), write a function that accepts a 32-bit single-precision variable as input. Extract the sign, exponent, and mantissa from the bytes of the floating-point variable and display them. Remove the bias term from the exponent before displaying its value and display the mantissa as a decimal number. Test the program with the values 0, -0, 1, -1, 6.674e-11, 1.0e38, 1.0e39, 1.0e-38, and 1.0e-39. The numeric values listed here containing e are using the C/C++ text representation of floating-point numbers. For example, 6.674e-11 means 6.674 x 10^-11.

Answer

The Ex__1_float_format.cpp C++ file contains the code for this exercise:

// Ex__1_float_format.cpp
#include <iostream>
#include <cstdint>
void print_float(float f)
{
    const auto bytes = static_cast<uint8_t*>(static_cast<void...

Chapter 10: Modern Processor Architectures and Instruction Sets

Exercise 1

Install the free Visual Studio Community edition, available at https://visualstudio.microsoft.com/vs/community/, on a Windows PC. After installation is complete, open the Visual Studio IDE and select Get Tools and Features… under the Tools menu. Install the Desktop development with C++ workload:

1. In the Windows search box in the taskbar, begin typing Developer Command Prompt for VS 2022. When the app appears in the search menu, select it to open Command Prompt.
2. Create a file named hello_x86.asm with the content shown in the source listing in the x86 assembly language section of Chapter 10, Modern Processor Architectures and Instruction Sets.
3. Build the program using the command shown in the x86 assembly language section of Chapter 10, Modern Processor Architectures and Instruction Sets, and run it. Verify that the output Hello, Computer Architect! appears on the screen.

...

Chapter 11: The RISC-V Architecture and Instruction Set

Exercise 1

Visit https://www.sifive.com/software/ and download Freedom Studio. Freedom Studio is an Eclipse IDE-based development suite with a complete set of tools for building an RISC-V application and running it on a hardware RISC-V processor or in the emulation environment included with Freedom Studio. Follow the instructions in the Freedom Studio User Manual to complete the installation. Start Freedom Studio and create a new Freedom E SDK project. In the project creation dialog, select qemu-sifive-u54 as the target (this is a single-core 64-bit RISC-V processor in the RV64GC configuration). Select the hello example program and click on the Finish button. This will start a build of the example program and the RISC-V emulator. After the build completes, the Edit Configuration dialog box will appear. Click on Debug to start the program in the emulator debug environment. Single-step through the program and verify that the...

Chapter 12: Processor Virtualization

Exercise 1

Download and install the current version of VirtualBox. Download, install, and bring up Ubuntu Linux as a VM within VirtualBox.

Connect the guest OS to the internet using a bridged network adapter. Configure and enable clipboard sharing and file sharing between the Ubuntu guest and your host operating system.

Answer

Perform the following steps:

1. Download the VirtualBox 6.1 (or later version) installer from https://www.virtualbox.org/wiki/Downloads. Be sure to select the version appropriate for your host operating system.
2. Run the VirtualBox installer and accept the default prompts.
3. Download a VirtualBox image of 64-bit Ubuntu Linux. One source for such an image is https://www.osboxes.org/ubuntu/. If the image is in a compressed format, uncompress it. Use 7-Zip (https://www.7-zip.org/) if the filename ends with .7z. After unzipping, the VirtualBox disk image filename will have the extension .vdi.
...

Chapter 13: Domain-Specific Computer Architectures

Exercise 1

Draw a block diagram of the computing architecture for a system to measure and report weather data 24 hours a day at 5-minute intervals using SMS text messages. The system is battery-powered and relies on solar cells to recharge the battery during daylight hours. Assume the weather instrumentation consumes minimal average power, only requiring full power momentarily during each measurement cycle.

Answer

Based on the performance requirements, a processor capable of entering a very low power state for minutes at a time should be able to operate from a moderately sized battery for days at a time. By only powering weather sensors when necessary to take a measurement, and only powering the cellular transceiver when it is time to transmit data, power usage is minimized.

The following diagram represents one possible configuration for this system:

Figure 5: Initial weather data collection system diagram...

Chapter 14: Cybersecurity and Confidential Computing Architectures

Exercise 1

Where supported, set up two-factor authentication for all your internet-accessible accounts containing data that you care about. This includes bank accounts, email accounts, social media, code repositories (if you are a software developer), medical services, and anything else you value. Ensure at all stages that you are using only information and software applications from trusted sources.

Answer

A comprehensive list of websites and their support (or non-support) for two-factor authentication is available at 2FA Directory (https://2fa.directory/). 2FA is an abbreviation for two-factor authentication.

The most common method for implementing two-factor authentication is for the site to send an SMS text containing a code to the phone number associated with the account after the user enters a valid username and password.

The code is often a 6-digit number that the user must provide to the...

Chapter 15: Blockchain and Bitcoin Mining Architectures

Exercise 1

Visit the blockchain explorer at https://bitaps.com and locate the list of last blocks on that page. Click on a block number and you will be presented with a display containing the hexadecimal listing of the block header along with its SHA-256 hash. Copy both items and write a program to determine if the hash provided is the correct hash of the header. Remember to perform SHA-256 twice to compute the header hash.

Answer

The Python file Ex__1_compute_block_hash.py contains the block header hashing code:

#!/usr/bin/env python
"""Ex__1_compute_block_hash.py: Answer to Ch 15 Ex 1."""
# This is a solution for Bitcoin block 711735
# See https://bitaps.com/711735
import binascii
import hashlib    
# The block header copied from bitaps.com
header = '00000020505424e0dc22a7fb1598d3a048a31957315f' + \
    '737ec0d00b0000000000000000005f7fbc00ac45edd1f6ca7' + \...

Chapter 16: Self-Driving Vehicle Architectures

Exercise 1

If you do not already have Python installed on your computer, visit https://www.python.org/downloads/and install the current version. Ensure Python is in your search path by typing python –version at a system command prompt. You should receive a response similar to Python 3.10.3. Install TensorFlow (an open source platform for machine learning) with the command (also at the system command prompt) pip install tensorflow. You may need to use the Run as administrator option when opening the command prompt to get a successful installation. Install Matplotlib (a library for visualizing data) with the command pip install matplotlib.

Answer

The Windows batch file Ex__1_install_tensorflow.bat contains the commands to install TensorFlow and Matplotlib:

REM Ex__1_install_tensorflow.bat: Answer to Ch 16 Ex 1.
REM This batch file installs TensorFlow and Matplotlib in Windows.
REM Python must be installed (see https...

Chapter 17: Future Directions in Computer Architectures

Exercise 1

Install the Qiskit quantum processor software development framework by following the instructions at https://qiskit.org/documentation/getting_started.html. The instructions suggest installation of the Anaconda (https://www.anaconda.com/) data science and machine learning toolset. After installing Anaconda, create a Conda virtual environment named qiskitenv to contain your work on quantum code and install Qiskit in this environment with the command pip install qiskit. Be sure to install the optional visualization dependencies with the command pip install qiskit-terra[visualization].

Answer

1. Download the Anaconda installer from https://www.anaconda.com/distribution/. Select the current version and the appropriate 32-bit or 64-bit variant for your host computer.
2. Run the Anaconda installer and accept the defaults. Close the installer after it completes.
3. Start Anaconda from the Windows search...