3.1 - computer architecture 🏗

Question 1

what does a modern CPU have inside?

Answer 1

an ALU, CU, and some register buses

Question 2

who paved the way for CPUs to look like this and why?

Answer 2

John von Neumann - he did this to allow computers to operate with less human intervention through his stored program concept

Question 3

what does ALU stand for and what are its functions?

Answer 3

ALU = arithmetic + logic unit; it carries functions like logical shifts, subtractions, and logic gate operations while a program’s running on a device

Question 4

what does CU stand for and what are its functions?

Answer 4

CU = control unit; it reads instructions from the program counter to interpret them through a fetch-decode-execute cycle while also helping keep data flow in a device in sync

Question 5

how does the CPU access data and programs on a device?

Answer 5

it takes them from backing stores like HDDs and SSDs to temporarily put them into the RAM (aka IAS) to allow for faster R/W ops

Question 6

what special purpose registers are in a von Neumann-system CPU?

Answer 6

the CIR (current instruction register), ACC (accumulator), MAR (memory address register), MDR (memory data register), and program counter (PC)

Question 7

what does the CIR do?

Answer 7

it stores the instruction currently being decoded+executed

Question 8

what does the accumulator do?

Answer 8

it temporarily stores data during ALU calculations

Question 9

what does the MAR do?

Answer 9

it stores the memory location address being written to

Question 10

what does the MDR do?

Answer 10

it stores data that’s either already read or about to be written

Question 11

what does the PC do?

Answer 11

it stores the address of the next instruction to be read

Question 12

what do device memory partitions contain?

Answer 12

binary addresses that can be written into the MAR to have their contents put into the MDR

Question 13

what system buses exist in von Neumann architecture?

Answer 13

the address, data, and control buses

Question 14

what does the address bus do?

Answer 14

it unidirectionally carries addresses from the CPU to device memory and can address more memory locations simultaneously the wider it is

Question 15

what does the data bus do?

Answer 15

it bidirectionally carries data between the CPU and device memory and can process more bits simultaneously the wider it is

Question 16

what does the control bus do?

Answer 16

it bidirectionally carries signals between the control unit and other device components and is always 8 bits wide

Question 17

what’s meant by the “fetch” part of the FDE (fetch-decode-execute) cycle?

Answer 17

it’s when the MDR fetches the next instruction from a currently-stored memory address in the MAR and keeps it with itself so its contents can be copied to the CIR and the PC incremented by 1

Question 18

what’s meant by the “execute” part of the FDE cycle?

Answer 18

it’s when instructions that’ve already been decoded are passed as control signals by the CPU to the components where they’d be most appropriate

Question 19

how do system clock speeds affect device performance?

Answer 19

increasing them could potentially make a device work faster as long as they don’t exceed a certain limit beyond which overclocking occurs

Question 20

what could happen in the event of overclocking?

Answer 20

the device’s CPU could overheat and instructions could also end up being out-of-sync

Question 21

how does cache memory work?

Answer 21

it stores a set of frequently accessed instructions and data within the CPU itself so they can be accessed more quickly than if they were stored in the device RAM

Question 22

how does the number of cores in a CPU affect device performance?

Answer 22

increasing that number could potentially reduce the need for clock speed changes but might also be a burden on communication between CPU cores as well

Question 23

what are ops in a device’s low-level instruction set divided into?

Answer 23

the opcode (informs about the necessities to the CPU) and operand (contains the must-be-acted-on data/memory registers)

Question 24

what are some examples of device instruction sets?

Answer 24

x86 (32-bit), x64 (64-bit), i386 (32-bit), and Itanium (64-bit)

Question 25

what are embedded systems?

Answer 25

they’re hardware/software combos designed to carry some specific functions that’re easy to fit into devices but can be hard to upgrade to the advantage of next-gen tech

Question 26

where can some examples of embedded systems be found IRL?

Answer 26

washing machines, digital weighing scales, arcade machines, vending machines, lighting systems, security devices, dumb TVs, and vehicle satnav systems