Computer Architecture is the study of a computer's internal structure, focusing on the CPU, memory, and data paths. It defines how computers process, store, and communicate data. Understanding it helps optimize performance and is essential for system design, embedded development, and low-level programming. Think of it as a computer's blueprint.

MCQ questions

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1. Gray Code for decimal 7 is 100

Explanation: Gray code changes only one bit between successive values.
🔍 Mnemonic: Think "7 in binary is 111" → flip the last bit to get Gray → 100.

Reference: Binary to Gray

2. 9’s complement of 46 is 53

Explanation: 9's complement = 99 - number.
🧮 Mnemonic: "Subtract from 9 for each digit": 9-4=5, 9-6=3 → 53.

3. Cache memory is implemented using SRAM

Explanation: SRAM is faster and used for cache due to its low access time.
🧠 Mnemonic: "S" in SRAM for "Speed" → Cache.

4. Number of address lines required for 512 bytes RAM is 9

Explanation: 2⁹ = 512 → needs 9 address lines.
📏 Mnemonic: Remember "2ⁿ = memory size", so log₂(512) = 9.

5. Addressing mode in MOV A,B is Register Addressing

Explanation: Operands are CPU registers.
🎯 Mnemonic: MOV between registers = register mode.

6. Advantage of Modular programming is c) Change is local to module

Explanation: Only the module where the change is made is affected.
🧩 Mnemonic: Module = Isolated box → change inside won’t spill.

7. Program performs 3 × content of 2501H → store at 2502H

Explanation: ADD A adds accumulator twice → 3x original.
🔁 Mnemonic: LDA → ADD → ADD = 3×.

8. Multiplexer is also known as a Data Selector

Explanation: It selects one input from many.
📦 Mnemonic: MUX = Multiple Inputs, X = Selector.

9. CPU uses Bus Grant to signal high impedance state to DMA

Explanation: BG signals DMA to take control.
🎯 Mnemonic: BG = "Bus Given".

10. Memory is connected to address lines

Explanation: Address lines locate memory cells.
📡 Mnemonic: Address = Access memory.

11. Memory performance is measured by Access Time

Explanation: Time to read/write from memory.
⏱️ Mnemonic: Access time = speed of access.

12. Translator program is Compiler; BCD expresses decimal as 4-bit binary

Explanation: Compiler translates to machine code; BCD uses 4 bits per digit.
🧠 Mnemonic: BCD = Binary Coded Decimal → 4 bits/digit.

13. RISE = Reduced Instruction Set Execution

Explanation: Related to RISC.
🔤 Mnemonic: RISC = Reduced Instructions → RISE in speed.

14. Multiplexers for 8 registers, 4 bits = 4 multiplexers

Explanation: One 8:1 MUX per bit → 4 bits = 4 MUX.
📐 Mnemonic: Bits = number of MUX needed.

15. MAR = Memory Address Register

Explanation: Holds address of data to be fetched.
🏷️ Mnemonic: MAR → "Marks Address to Read".

16. Transfer R2 ← R1 executes when Enable Signal is active

Explanation: Needs control signal to trigger.
🎮 Mnemonic: No enable = No move.

17. DMA = Direct Memory Access

Explanation: Device accesses memory directly without CPU.
🔄 Mnemonic: DMA = Direct → Memory.

18. Logical shift transfers 0 through serial input

Explanation: Logical shift inserts zero.
🔢 Mnemonic: Logic is clean → always add 0.

19. Memory from 0000 to 7FFF = 32 KB

Explanation: 7FFF = 32767 + 1 = 32 KB.
📦 Mnemonic: 7FFF → 2¹⁵ locations → 32 KB.

20. 8085 Immediate mode: MVI A, 32H

Explanation: MVI loads immediate value.
📝 Mnemonic: MVI = Move Immediate.

21. 9’s complement of 546700 is 453299

Explanation: 999999 - 546700 = 453299.
🧮 Mnemonic: 9 - each digit.

22. Multiplexers for 8 registers, 16 bits = 16 multiplexers

Explanation: 1 per bit → 16 bits = 16 MUX.
📐 Mnemonic: Bits = number of MUX.

23. Multiprocessor system components: Processors + Shared Memory

Explanation: Multiple CPUs accessing common memory.
🔗 Mnemonic: Multi-core → multi-CPU.

24. CISC = Complex Instruction Set Computer

Explanation: Rich set of complex instructions.
📚 Mnemonic: CISC = Complex.

25. PC points to Next Instruction

Explanation: PC stores address of next instruction.
🧭 Mnemonic: PC = Program Counter → Next.

26. ROR = Rotate Right

Explanation: Bits rotate right.
🔄 Mnemonic: ROR = Right Over Rotate.

27. Overlapping instruction execution is Pipelining

Explanation: Concurrent instruction execution.
🚿 Mnemonic: Like water pipe – flow together.

28. Zero address instruction → Operands in Stack

Explanation: Implicit use of top of stack.
📚 Mnemonic: Zero address = Stack.

29. Physical memory is divided into Pages

Explanation: Virtual memory uses paging.
📖 Mnemonic: Memory = pages like book.

30. Bi-directional bus: Data bus

Explanation: Data flows in both directions.
🔁 Mnemonic: Data comes and goes.

31. Minimum time between reads = Memory Cycle Time

Explanation: Includes access + recovery time.
⏲️ Mnemonic: Cycle = Full round.

32. Arithmetic/logic results stored in Accumulator or Register

Explanation: ALU outputs go to accumulator.
📥 Mnemonic: Accumulates result.

33. Cache memory implemented using SRAM

Explanation: Fast and doesn’t need refreshing.
⚡ Mnemonic: Cache = Fast → SRAM.

34. Page replacement goal: Minimize Page Faults

Explanation: Avoid memory access delays.
🚫 Mnemonic: Less faults = fast.

35. Cache memory purpose: Speed up data access

Explanation: Stores frequently used data.
🏎️ Mnemonic: Cache = Speed boost.

36. Data hazards occur when Data not available for next instruction

Explanation: One instruction needs result of another.
🚧 Mnemonic: Hazard = Wait for data.

37. Transfer R2 ← R1 executes when Control signal active

Explanation: Needs timing/control.
🔒 Mnemonic: Controlled move.

38. Computer registers: R1, R2…

Explanation: Registers labeled for use.
🔢 Mnemonic: R = Register.

39. Selective-complement and clear = AND + NOT microoperations

Explanation: Clear = AND with 0; Complement = NOT.
🛠️ Mnemonic: A + N = AND + NOT.

40. Output = 1 when inputs = 0 → NOR gate

Explanation: NOR = NOT OR.
🔘 Mnemonic: All 0 = 1 only in NOR.

41. Special to temporal code via Counter

Explanation: Converts static to time-based code.
⏳ Mnemonic: Count time.

42. Simplified expression: (X + Y)(X + Z) = X + YZ

Explanation: Boolean simplification.
📐 Mnemonic: Apply distributive rule.

43. Gates for half adder: XOR and AND

Explanation: XOR = sum, AND = carry.
➕ Mnemonic: X + A = Half Adder.

44. Fastest logic: ECL

Explanation: Emitter Coupled Logic is fastest.
🚀 Mnemonic: ECL = Extra Crazy Logic speed.

45. Volatile memory: RAM

Explanation: RAM loses data when off.
🔌 Mnemonic: Volatile = Vanishes.

46. AND gate (3-inputs): Output = 1 when A, B, C = 1

Explanation: All inputs must be high.
💡 Mnemonic: AND = All Needed Data.

47. Binary to decimal: 10010.011 = 18.375

Explanation: 16+2 + 0.25 + 0.125 = 18.375.
🧮 Mnemonic: Whole + fractional.

another example

48. Flip-flops for MOD-32 = 5

Explanation: 2⁵ = 32.
🧠 Mnemonic: MOD N → log₂N.

49. 0010 in → After 2 clocks = 1 0 0 0

Explanation: Shifts right 2 times.
🔁 Mnemonic: Shift twice = rotate bits.

50. XNOR = A'B' + AB

Explanation: True when inputs match.
💞 Mnemonic: XNOR = eXactly NOR.

51. Y = A + AB + ABC simplifies to A

Explanation: A is common in all.
🧠 Mnemonic: A once is enough.

52. 100.0 (binary) = 4.0

Explanation: 1×2² = 4.
📐 Mnemonic: Binary place values.

53. BCD of 32 = 0011 0010

Explanation: 3 = 0011, 2 = 0010.
🧾 Mnemonic: BCD = 4-bit per digit.

54. Sequential circuit: Has memory/feedback

Explanation: Depends on previous states.
🔁 Mnemonic: Sequence → State → Memory.

55. Term in POS: Maxterm

Explanation: OR of variables in each term.
📖 Mnemonic: POS = Product of Sums → Maxterm.

56. Decoder with 4 select lines: 16 outputs

Explanation: 2⁴ = 16 outputs.
🔢 Mnemonic: 2ⁿ outputs.

57. CCD = Charge Coupled Device

Explanation: Used in imaging sensors.
📸 Mnemonic: Camera = CCD.

58. To build n-input NAND from 2-inputs: n-1

Explanation: Binary tree of gates → needs n-1.
🌲 Mnemonic: Build tree → one less node than leaves.

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Cheat sheet ( formula and full forms )

Here’s the completed Computer Architecture Cheat Sheet with Formulas, Full Forms, and helpful mnemonics:

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🧠 Computer Architecture Cheat Sheet

📘 Important Formulas

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🔤 Full Forms

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🛠 Boolean Algebra Laws

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🔄 Number System Tricks

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🔍 Instruction Formats & Modes

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🧮 Logic Gate Summary

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📦 Memory Hierarchy (Fast → Slow)

1. Registers

2. Cache (SRAM)

3. Main Memory (DRAM)

4. SSD / HDD

5. Optical / Tape

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🧩 Microoperations Types

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Here's your full explanation in clean Markdown format — perfect for study notes or a blog post:

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Let’s break down the concept of cache memory, cache mapping techniques, and how virtual memory works in a simple and clear way.

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What is Cache Memory? different type of mapping and implementation of virtual memory ?

Cache is a small, fast memory located close to the CPU that stores frequently accessed data from the main memory (RAM) to reduce access time.

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Cache Mapping Techniques

When the CPU needs data, it checks the cache. But how does it know where to look in the cache? That's where cache mapping comes in. There are three main types:

1. 🔹 Direct Mapping

• Each block of main memory maps to exactly one cache line.

• Fast but less flexible.

Formula:

Cache Line Index = (Main Memory Block Address) % (Number of Cache Lines)

Example: If memory block 5 and 13 both map to cache line 5 (because 5 % 8 = 5 and 13 % 8 = 5), then if one is loaded, the other will evict it.

Pros: Simple & fast Cons: Collisions can occur easily (conflicts).

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2. 🔸 Fully Associative Mapping

• Any block can be placed anywhere in the cache.

• Most flexible but slowest for searching.

Needs: A search through all tags for a match.

Pros: No conflict misses. Cons: Expensive hardware (comparators for all lines).

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3. 🔷 Set-Associative Mapping

• Compromise between the above two.

• Cache is divided into sets, each with n lines (n-way set associative).

• A memory block maps to a specific set, but can go into any line within that set.

Formula:

Set Index = (Block Address) % (Number of Sets)

Example: 4-way set associative cache with 16 lines = 4 sets, each with 4 lines.

Pros: Balances speed and flexibility. Cons: More complex than direct mapping.

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🧮 Quick Summary Table

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💾 How Virtual Memory Works

Virtual memory is an OS-level abstraction that gives each process the illusion of a large, continuous memory, even if the physical memory is small.

🔧 Key Concepts:

• Virtual Address (used by programs)

• Physical Address (actual RAM location)

• Page: Fixed-size block of virtual memory (e.g., 4KB)

• Frame: Corresponding block in physical memory

🔄 Address Translation:

1. CPU generates a virtual address.

2. MMU (Memory Management Unit) uses a page table to translate it into a physical address.

3. If the page is not in RAM (page fault), it is loaded from disk.

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🔐 Virtual Memory Benefits:

• Isolation: Each process has its own address space.

• Multitasking: Easy to swap between processes.

• Larger Memory: Programs can use more memory than physically available via paging.

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💡 Paging vs Segmentation

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🧠 Mnemonic Tricks:

• D in Direct means Definite place.

• F in Fully Associative = Free placement.

• S in Set-Associative = Shared within a set.

• V in Virtual Memory = Vast space illusion.

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Here’s a concise explanation of hierarchical memory organization and the difference between Write-Through and Write-Back:

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2. what is Hierarchical Organization of Memory and walk through and write back ?

Hierarchical Organization of Memory (Top to Bottom)

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📝 Write-Through vs Write-Back (Cache Write Policies)

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🎯 Mnemonics:

• Write-Through: Write To RAM Too

• Write-Back: Write Back Later

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Sure! Here's everything in plain text (not Markdown or MDX) for easy reading or pasting into a regular document.

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2. What is locality of reference? Explain its types?

   What is hit and miss ratio in cache memory? Give formulas and example?

   What are the different types of ROM?

   What is the difference between RISC and CISC architectures?

1. Locality of Reference

Locality of reference refers to the tendency of a program to access the same or nearby memory locations frequently within a short period.

Types:

• Temporal Locality: Recently accessed data will likely be accessed again.

• Spatial Locality: Nearby memory locations are likely to be accessed soon.

• Sequential Locality: Instructions/data are accessed sequentially (like in loops).

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2. Cache Hit and Miss Ratio

• Hit: When requested data is found in cache.

• Miss: When data is not found in cache and must be fetched from main memory.

Formulas:

• Hit Ratio = (Number of Hits) / (Total Memory Accesses)

• Miss Ratio = (Number of Misses) / (Total Memory Accesses)

• Miss Ratio = 1 - Hit Ratio

Example:
If 90 hits and 10 misses in 100 accesses:

• Hit Ratio = 90 / 100 = 0.9 (90%)

• Miss Ratio = 10 / 100 = 0.1 (10%)

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3. Types of ROM (Read-Only Memory)

• ROM: Pre-programmed at the factory; cannot be modified.

• PROM: Programmable once by the user; cannot be erased.

• EPROM: Can be erased using UV light and reprogrammed.

• EEPROM: Can be erased electrically and reprogrammed many times.

• Flash Memory: A faster version of EEPROM; used in USB drives, SSDs.

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4. Difference Between RISC and CISC

Mnemonic:

• RISC → Really Intelligent Simple Code

• CISC → Complex Instructions Save Code

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what is pagging and it’s technique ?

Von-Neuman Architecture ?

Vector proceesing and it’s application?

Paging is a memory management technique where the logical memory is divided into fixed-size blocks called pages, and physical memory is divided into blocks of the same size called frames.

• The Operating System maintains a page table to map logical pages to physical frames.

• Paging helps to eliminate external fragmentation.

• It allows non-contiguous allocation of memory, improving efficiency.

Technique:

• When a process needs memory, its pages are loaded into available frames.

• Address translation is done using the page number and offset.

• If the required page is not in RAM, a page fault occurs, and it's fetched from disk.

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Von-Neumann Architecture is a computer architecture model where:

• Program and data share the same memory and same bus.

• Instructions are fetched and executed sequentially.

• It consists of:

  • ALU (Arithmetic Logic Unit)

  • CU (Control Unit)

  • Memory Unit

  • Input/Output devices

  • Registers

Limitation: Known as the Von-Neumann Bottleneck, where a single bus slows down instruction/data access.

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Vector Processing is a type of parallel computing where a single instruction operates on multiple data elements (SIMD - Single Instruction, Multiple Data).

• It uses vector processors or array processors.

• Efficient for mathematical and scientific computations involving large data sets.

Applications:

• Weather forecasting

• Image and signal processing

• Machine learning and deep learning

• Scientific simulations (physics, chemistry, biology)

• Aerospace and defense modeling

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5. what is pipeling give example? maths on speed up ratio

   Here’s a clear explanation of pipelining with an example and the formula for speedup ratio:

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   What is Pipelining?

   Pipelining is a technique used in CPUs to improve instruction throughput by overlapping the execution of multiple instructions.

   • The execution process is divided into stages (like fetch, decode, execute, memory access, write back).

   • Different instructions are processed simultaneously at different stages.

   • This increases CPU instruction throughput (more instructions per unit time).

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Example of Pipelining

Suppose an instruction takes 5 stages, each taking 1 nanosecond:

• Without pipelining:
  To execute 5 instructions, total time = 5 instructions × 5 ns = 25 ns.

• With pipelining:
  After the pipeline is filled, one instruction completes every 1 ns.
  Total time to execute 5 instructions = 5 ns (pipeline fill) + (5 - 1) × 1 ns = 9 ns.

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Speedup Ratio

Speedup due to pipelining is:

$$\text{Speedup} = \frac{\text{Time without pipelining}}{\text{Time with pipelining}}$$

If

• ( n ) = number of instructions,

• ( k ) = number of pipeline stages,

• ( t ) = time per stage,

Then,

$$\text{Time without pipelining} = n \times k \times t$$

$$\text{Time with pipelining} = (k + n - 1) \times t$$

Therefore,

$$\Rightarrow \text{Speedup} = \frac{n \times k \times t}{(k + n - 1) \times t} = \frac{n \times k}{k + n - 1}$$

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Example:

Suppose

• Number of instructions, ( n = 10 )

• Number of pipeline stages, ( k = 5 )

• Time per stage, ( t = 1 \text{ ns} )

Calculate the speedup.

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Step 1: Calculate time without pipelining

$$\text{Time without pipelining} = n \times k \times t = 10 \times 5 \times 1 = 50 \text{ ns}$$

Step 2: Calculate time with pipelining

$$\text{Time with pipelining} = (k + n - 1) \times t = (5 + 10 - 1) \times 1 = 14 \text{ ns}$$

Step 3: Calculate speedup

$$\text{Speedup} = \frac{50}{14} \approx 3.57$$

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Interpretation:
Pipelining makes the execution about 3.57 times faster than non-pipelined execution in this example.

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### Key points:

* For large nn, speedup approaches kk (number of stages).

* Ideal speedup is equal to the number of pipeline stages.

* Real-world speedup is less due to pipeline hazards and stalls.

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what is arithmetic pipelining? booths algorithm ( with example) ? IEEE-754 ? Fixed vs Floating point representation ?

1. Breaks complex arithmetic operations into multiple smaller stages.

2. Each pipeline stage performs one step (e.g., fetch, align, add, normalize, round).

3. Multiple arithmetic instructions processed simultaneously at different stages.

4. Increases throughput by overlapping instruction execution.

5. Speeds up overall arithmetic processing, improving CPU performance.

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1. Fixed Point:

   • Represents numbers with a fixed number of digits before and after the decimal point.

   • Good for simple, precise calculations like money or small range values.

2. Floating Point:

   • Represents numbers with a mantissa and exponent, allowing a wide range of values.

   • Used for scientific calculations needing large dynamic range.

3. Precision:

   • Fixed point has constant precision (limited range).

   • Floating point precision varies depending on the exponent.

4. Complexity and Hardware:

   • Fixed point arithmetic is simpler and faster in hardware.

   • Floating point arithmetic is more complex but handles very large/small numbers better.

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design 4 bit adder 4 bit incrementer diff type of shift micro operation memory read and write operation explain it and register transfer language

1. Design of 4-bit Adder

2. 4-bit Incrementer

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3. Different Types of Shift Operations

• Logical Shift Left (LSL): Shifts all bits left, inserting 0 on the right.

• Logical Shift Right (LSR): Shifts all bits right, inserting 0 on the left.

• Arithmetic Shift Right (ASR): Shifts bits right, replicating the sign bit (MSB) on the left (for signed numbers).

• Rotate Left (ROL): Bits shifted left; MSB is rotated to the LSB position.

• Rotate Right (ROR): Bits shifted right; LSB is rotated to the MSB position.

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4. Micro-Operations

• Micro-operations are basic operations performed on data stored in registers.

• Types:

  • Register Transfer: Moving data from one register to another (e.g., R1 → R2).

  • Arithmetic: Addition, subtraction, increment, decrement (e.g., R1 + R2 → R3).

  • Logic: AND, OR, XOR, NOT operations on register contents.

  • Shift: Bit shifts or rotates on register data.

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5. Memory Read and Write Operation

• Memory Read:

  • CPU places the address on the memory address register (MAR).

  • Sends a read signal to memory.

  • Data from memory location is placed on the memory data register (MDR).

  • Data is transferred to the CPU register.

• Memory Write:

  • CPU places the address on MAR.

  • Places data to be written into MDR.

  • Sends a write signal to memory.

  • Memory stores data from MDR into specified address.

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6. Register Transfer Language (RTL)

• RTL describes the data transfer and operations between registers in symbolic form.

• Example:

  • R1 ← R2 + R3 means: add contents of R2 and R3, store in R1.

  • MAR ← PC means: copy program counter value to memory address register.

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8. What is Memory Stack?

What is Memory Stack?

• A memory stack is a portion of main memory used to store temporary data like function calls, return addresses, and local variables.

• It works on Last In, First Out (LIFO) principle — the last item pushed is the first to be popped.

• The stack pointer (SP) keeps track of the current top of the stack in memory.

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2. What is Register Stack?

• A register stack is a stack implemented using CPU registers instead of memory.

• It provides fast data storage and retrieval using push and pop operations within the processor registers.

• Often used for temporary data, intermediate results, or storing return addresses in some CPU designs.

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3. Push and Pop in Register Stack

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9. design

• 4bit-alu design with micro operation.

• 4 bit bus system

• flowchart of addition and subtraction

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Address sequencing of micro-program control unit. Diff type of Address mode. DMA controller and it’s operator

1. Address Sequencing in Microprogrammed Control Unit

A microprogrammed control unit generates control signals using a sequence of microinstructions stored in control memory. The control address of the next microinstruction is determined using address sequencing.

Address Sequencing Techniques:

1. Incremental Sequencing – Next address = Current address + 1

2. Branching – Jumps to a microinstruction based on condition flags or opcode

3. Mapping – Direct mapping of instruction opcode to microinstruction address

4. Subroutine Call/Return – Supports CALL and RETURN using microprogram stack

These determine how control flows in executing instructions.

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2. Different Types of Addressing Modes

Addressing modes define how the operand (data) is accessed in an instruction. Common modes:

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3. DMA Controller and Its Operation

What is DMA?

DMA (Direct Memory Access) is a technique where data is transferred between memory and I/O devices without involving the CPU for each byte.

Components of DMA Controller:

• Address Register: Holds memory address for data transfer

• Count Register: Number of bytes to transfer

• Control Register: Controls read/write mode and transfer enable

• Data Bus Buffer: For transferring actual data

DMA Modes of Operation:

1. Burst Mode (Block Transfer): Entire block of data transferred in one go

2. Cycle Stealing: DMA takes control of bus for one cycle at a time

3. Transparent Mode: DMA works only when CPU is idle

Steps in DMA Transfer:

1. CPU gives control to DMA by setting up registers

2. DMA sends request to memory

3. Data is transferred directly between I/O device and memory

DMA sends interrupt to CPU after transfer is done

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Difference

• Micro programmed control unit vs hardwired control unit

• RISC vs CISC

• Memory mapped IO vs IO based IO

• Static Ram vs Dynamic Ram

Here are the clear differences between the requested pairs:

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✅ 1. Microprogrammed Control Unit vs Hardwired Control Unit

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✅ 2. RISC vs CISC

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✅ 3. Memory-Mapped I/O vs I/O-Mapped (Isolated) I/O

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✅ 4. Static RAM (SRAM) vs Dynamic RAM (DRAM)

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Diff mode of Data Transfer. FLYNN classification , Explaineach. Async mode of data transfer explain

1. Different Modes of Data Transfer

Data can be transferred between CPU, memory, and I/O devices using several modes:

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2. Flynn’s Classification (Computer Architecture)

Flynn's taxonomy classifies computer systems based on instruction and data streams.

Diagram:

Instruction →   Data →
SISD       :    One     One
SIMD       :    One     Many
MISD       :    Many    One
MIMD       :    Many    Many

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3. Asynchronous Mode of Data Transfer

In asynchronous data transfer, data is transmitted without using a shared clock between the sender and receiver. Instead, control signals or special bits (like start and stop bits) are used to coordinate the transfer.

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✅ Asynchronous Data Transfer – Key Aspects

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✅ Asynchronous Handshaking Signals

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13. Diff Interrupts and Instruction format

Types of Interrupts (with Explanation)

Interrupts are signals that divert the CPU to handle events immediately. They can be classified as:

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Instruction Format in Computer Architecture

Instruction format refers to how a CPU instruction is structured in binary form. Every instruction typically includes:

• Opcode: Operation to perform (e.g., ADD, MOV)

• Operands: Data to operate on (e.g., registers, memory addresses)

• Addressing mode info: Tells how to interpret operands

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✅ Types of Instruction Formats:

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Example Table for Instruction Format

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Here are easy mnemonics to remember types of interrupts and instruction formats effectively:

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✅ Mnemonics for Types of Interrupts

Use this phrase:

"Hi Sweetie, My New Vanilla Ice-Energy Smoothie Punches Everyone."

Each first letter maps to an interrupt type:

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✅ Mnemonic for Instruction Formats

Use this sentence:

"Zombies Only Taste Two Rotis, Dipped In Rice."

(You can repeat R for Register and Register Indirect.)

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Short note on

• DMA

• CAM

• IO interface

• Priority Interepts

• Virtual memory

✅ 1. DMA (Direct Memory Access)

1. Transfers data directly between memory and I/O devices without CPU.

2. Uses a DMA controller to manage transfers.

3. Frees the CPU for other tasks, improving efficiency.

4. Commonly used in disk drives, graphics, and audio.

5. Operates via modes like burst, cycle stealing, and block.

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✅ 2. CAM (Content Addressable Memory)

1. Also called associative memory.

2. Searches by data content, not by address.

3. All memory entries are compared simultaneously.

4. Fast data lookup, used in cache and TLB.

5. Expensive and used in special-purpose hardware.

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✅ 3. I/O Interface

1. Connects CPU with external input/output devices.

2. Manages communication, control, and data conversion.

3. Supports synchronous and asynchronous transfers.

4. Examples: keyboard controller, USB interface.

5. Can use memory-mapped or I/O-mapped techniques.

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✅ 4. Priority Interrupts

1. Assigns priority levels to multiple interrupt sources.

2. Ensures urgent tasks are handled first.

3. Managed using an interrupt controller.

4. Lower-priority interrupts wait if a higher one occurs.

5. Used in real-time and multitasking systems.

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✅ 5. Virtual Memory

1. Logical memory space larger than physical RAM.

2. Uses paging to map virtual to physical addresses.

3. Stores inactive pages in disk (swap space).

4. Improves multitasking and memory utilization.

5. Managed by MMU (Memory Management Unit).

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15. Explain logical microoperation arithmetic micro-operation data transfer micro operation 2's complement -> subtraction

    ✅ 1. Logical Micro-Operations

    These perform bitwise operations between registers.

    • Operations: AND, OR, XOR, NOT.

    • Example:
      R1 ← R2 AND R3
      (Performs bitwise AND between R2 and R3, stores in R1.)

    • Used for masking, setting, or clearing bits.

    • Operate on individual bits of the operand.

    • Fast and useful in bit-level manipulation.

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✅ 2. Arithmetic Micro-Operations

These perform basic arithmetic operations on register data.

• Operations: ADD, SUB, INCREMENT, DECREMENT, NEGATE.

• Example:
  R1 ← R2 + R3

• Used in performing arithmetic in ALU.

• Overflow and carry bits may be generated.

• Subtraction is often done using 2’s complement.

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✅ 3. Data Transfer Micro-Operations

These move data from one place to another.

• Operations: Transfer between registers or memory.

• Example:
  R1 ← R2
  (Copy data from R2 to R1.)

• Includes Memory Read/Write operations.

• Often part of control unit operations.

• No changes made to data—just moved.

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✅ 4. 2's Complement → Subtraction

• To subtract B from A, do:
  A - B = A + (2’s complement of B)

• Steps:

  1. Take 1’s complement of B.

  2. Add 1 → now you have 2’s complement of B.

  3. Add it to A: A + (~B + 1)

• Example:
  6 - 4 = 6 + (-4) → 6 + (2's comp of 4)

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16. ai*bi+ci where i=[1 to 6 ] design the pipeline for it. What is parallel processing ? Why parallel processing is better than serial processing ?

    Parallel Processing

    • Definition: Simultaneous processing of multiple tasks using multiple processors or processing units.

    • Key Concepts:

      • Data Parallelism: Same operation on multiple data elements simultaneously.

      • Task Parallelism: Different tasks are processed concurrently.

Advantages of Parallel Processing over Serial Processing:

• Speed: Processes large data sets faster by dividing tasks.

• Efficiency: Utilizes multiple CPU cores effectively.

• Scalability: Easily scales with additional processors.

• Performance: Reduces execution time, especially in computationally intensive applications.

Parallel vs. Serial Processing:

• Parallel Processing:

  • Tasks are divided among multiple processors.

  • Efficient for data-intensive operations.

  • More complex to program and synchronize.

• Serial Processing:

  • Tasks are executed one after another.

  • Simpler to implement but slower for large datasets.

• Which is Better?

  • Parallel processing is better when tasks can be performed independently and data can be divided. It significantly improves performance for large-scale computations.

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pegging vs segmentation , vector vs non-vector Interrupt , Bootstrap loader store in ROM not in RAM why ?

Paging vs. Segmentation

• Paging:

  • Divides memory into fixed-size pages.

  • Logical address space is divided into equal-sized pages.

  • Physical memory is divided into equal-sized frames.

  • No relation between pages and program structure.

  • Eliminates external fragmentation but may cause internal fragmentation.

• Segmentation:

  • Divides memory into variable-sized segments.

  • Each segment corresponds to a logical unit, like a function or data structure.

  • Provides logical division of the program.

  • Can cause external fragmentation.

Vectored vs. Non-Vectored Interrupts

• Vectored Interrupts:

  • Each interrupt has a predefined memory address.

  • CPU directly jumps to the interrupt service routine (ISR).

  • Faster as the address is fixed and known in advance.

• Non-Vectored Interrupts:

  • The interrupting device must provide the address of the ISR.

  • CPU needs to fetch the ISR address, causing a delay.

  • More flexible as any device can specify its own address.

Why is the Bootstrap Loader Stored in ROM and Not in RAM?

• Bootstrap Loader:

  • A small program that loads the operating system into memory during the boot process.

• Stored in ROM because:

  • ROM is non-volatile, so it retains data when the computer is turned off.

  • The bootstrap loader needs to be available immediately after power on.

  • Storing it in RAM would erase the loader when the system shuts down.

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