Semiconductor Memories MCQ Quiz - Objective Question with Answer for Semiconductor Memories - Download Free PDF

Explanation:

A memory chip has a capacity of 4 kB. To determine the number of address lines required, we need to understand the relationship between memory capacity and address lines. The capacity of a memory chip is the product of the number of addressable memory locations and the size of each memory location.

Firstly, 4 kB (kilobytes) needs to be converted into bytes. Since 1 kB = 1024 bytes, we have:

4 kB = 4 × 1024 bytes = 4096 bytes

Each memory location in a typical memory chip stores 1 byte of data. Therefore, the memory chip with a capacity of 4096 bytes has 4096 addressable memory locations.

The number of address lines required (n) can be determined using the formula:

Number of addressable memory locations = 2ⁿ

Setting this equal to the number of memory locations we have:

2ⁿ = 4096

To solve for n, we take the logarithm base 2 of both sides:

n = log₂(4096)

Since 4096 is a power of 2 (specifically, 2¹²), we have:

n = 12

Therefore, 12 address lines are required to address 4096 memory locations.

Hence, the correct answer is option 2, which is 12.

To increase the word size (i.e., the number of bits in each word that the CPU can read or write in one operation), the system typically uses parallel memory modules.

🧠 How it works:

• If each memory chip/module is, for example, 8 bits wide, and you need a 32-bit word, then you can connect 4 such modules in parallel.

• Each module contributes a portion (like 8 bits) of the full word.

• All modules are accessed simultaneously, giving you a wider word size.

Additional Information

The correct answer is Programmable read-only memory

Key Points

• PROM stands for Programmable Read-Only Memory.
• Read-only memory (ROM) is a type of memory that is used in electronics and computers.
• It is a non-volatile memory, that is, information stored in such memory is permanent and cannot be changed.
• The other two types of ROM are
  • Electrically Erasable Programmable ROM (EEPROM)
  • Erasable Programmable ROM (EPROM)

Additional Information

• Primary memory can be divided into RAM (Random Access Memory) and ROM (Read Only Memory)

The correct answer is Primary Memory.

Key Points

• Random Access Memory (RAM) is a type of primary memory used by computers to store data and machine code currently being utilized.
• RAM is volatile memory, meaning it loses all stored data when the computer is powered off.
• It allows for fast read and write operations, making it essential for the efficient execution of tasks and programs.
• RAM is directly connected to the CPU, enabling quick access to data without relying on slower storage devices.
• Examples of primary memory include RAM and ROM, with RAM being the most commonly used for real-time operations.

Additional Information

• Primary Memory
  • Primary memory refers to the memory that the CPU can directly access. It includes RAM and ROM.
  • RAM (Random Access Memory) is used for temporary storage and is volatile.
  • ROM (Read-Only Memory) is non-volatile and contains essential instructions like the bootloader.
  • Primary memory is faster but has lower storage capacity compared to secondary memory.
• Secondary Memory
  • Secondary memory is used for long-term data storage and is non-volatile.
  • Examples include hard drives, SSDs, CDs, and USB drives.
  • It is slower compared to primary memory but has significantly higher storage capacity.
• Cache Memory
  • Cache memory is a small, high-speed memory located inside or close to the CPU.
  • It stores frequently accessed data and instructions to enhance processing speed.
  • Cache memory is categorized into levels (L1, L2, L3) based on proximity to the CPU.
• Volatile vs. Non-Volatile Memory
  • Volatile memory requires power to retain data (e.g., RAM).
  • Non-volatile memory retains data even when the computer is powered off (e.g., ROM, SSD).

Explanation:

The Remaining Address Line of Bus:

Definition: In a computer system, the address bus is responsible for carrying the addresses from the CPU to the memory or other devices. This bus is used to specify the location where data is to be read from or written to. The remaining address line of the address bus, after decoding, is used to generate the chip select signal. This signal is crucial for enabling the specific memory chip or peripheral device that the CPU intends to communicate with.

Working Principle: The address bus consists of multiple lines, each line representing a bit in the address. The decoding process involves interpreting the binary address to select a specific memory location or device. The remaining address line, after decoding, is utilized to generate the chip select signal, which activates the appropriate device for communication.

This option correctly identifies that the remaining address line of the address bus is used to generate the chip select signal. The address bus carries the address information, and the decoding process interprets this information to generate the necessary control signals, including the chip select signal.

The Correct Answer is "Cache Memory".

Important Points

Cache Memory :

• Cache Memory is a special very high-speed memory.
• It is used to speed up and synchronizing with a high-speed CPU. Cache memory is costlier than main memory or disk memory but economical than CPU registers.
• Cache memory is an extremely fast memory type that acts as a buffer between RAM and the CPU.
• It holds frequently requested data and instructions so that they are immediately available to the CPU when needed.
• Cache memory is used to reduce the average time to access data from the Main memory.

Additional Information

Secondary Memory​ :

• It is non-volatile, i.e. it retains data when power is switched off.
• It is large capacities to the tune of terabytes.
• It is cheaper as compared to the primary memory.
• Depending on whether the Secondary memory device is part of the CPU or not, there are two types of secondary memory – fixed and removable.

 Auxiliary Memory :

• Auxiliary memory is the non-volatile memory lowest-cost, highest-capacity, and slowest-access storage in a computer system.
• It is where programs and data kept for long-term storage or when not in immediate use.
• Such memories tend to occur in two types-sequential access (data must access in a linear sequence) and direct access (data may access in any sequence).
• The most common sequential storage device is the hard disk drives, whereas direct-access devices include rotating drums, disks, CD-ROMs, and DVD-ROMs.
• It used as permanent storage of data in mainframes and supercomputers.

Virtual Memo :

• A computer can address more memory than the amount physically installed on the system.
• This extra memory is actually called virtual memory and it is a section of a hard disk that's set up to emulate the computer's RAM.
• The main visible advantage of this scheme is that programs can be larger than physical memory.
• Virtual memory serves two purposes.
  • First, it allows us to extend the use of physical memory by using the disk.
  • Second, it allows us to have memory protection because each virtual address is translated to a physical address.

Random Access Memory (RAM):

• This memory allows writing as well as reading of data, unlike ROM which does not allow writing of data on to it.
• It is volatile storage because the contents of RAM are lost when the power (computer) is turned off.
• If we want to store the data for later use, we have to transfer all the contents to a secondary storage device.
• Hence, RAM is a temporary memory device. 

The memory of the computer is divided into two categories:
1. Primary Memory
2. Secondary Memory

1. Primary memory also called main memory or internal memory provides temporary storage of programs in execution and the data being processed. It is known as immediate access storage as this is the portion of the CPU that can be accessed directly. 

Primary memory can be further grouped into Random Access Memory (RAM) and Read-Only Memory (ROM).

2. Secondary or backing Memory

It maintains a permanent record of data and programs, maintains a store for the program and data being processed if the main memory cannot accommodate the data and program, and acts as an input/output device.

In a DRAM, a capacitor to store a bit of data is used along with a MOSFET (transfer device) which acts as a switch. The circuit is as shown –

In a DRAM:

• Periodic refreshing is required.
• The information is stored in a capacitor.
• Both read and write operations cannot be performed simultaneously.

Important Points

Concept:

• EPROM and EEPROM is a type of ROM.
• Data in ROM can be accessed randomly and hence EPROM and EEPROM are random access memory.

Important Points:

• EPROM is an erasable programmable read-only memory.
• It is a non-volatile memory that means its data will be retained even when the power is turned off.
• EEPROM (electrically erasable programmable read-only memory) is a user-modifiable read-only memory (ROM) that can be erased and reprogrammed (written to) repeatedly through the application of higher than normal electrical voltage.

• In computing, an optical disc drive (ODD) is a disc drive that uses laser light or electromagnetic waves within or near the visible light spectrum as part of the process of reading or writing data to or from optical discs.
• Compact discs, DVDs, and Blu-ray discs are common types of optical media which can be read and recorded by such drives.
• The CD drive shines a laser at the surface of the CD and can detect the reflective areas and the bumps by the amount of laser light they reflect.
• The drive converts the reflections into 1s and 0s to read digital data from the disc

Note:

Compact disc (CD) is a digital optical disc data storage format that was co-developed by Philips and Sony and released in 1982. The format was originally developed to store and play only sound recordings (CD-DA) but was later adapted for storage of data (CD-ROM).

The conversion of memory is given below.

1 TB = 1024 GB

1 GB = 1024 MB

1 MB = 1024 kB

1 kB = 1024 Byte

In a DRAM, a capacitor is used to store a bit of data along with a MOSFET (transfer device) which acts as a switch.

The circuit is as shown:

In a DRAM:

• Periodic refreshing is required.
• The information is stored in a capacitor.
• Both read and write operations cannot be performed simultaneously.

For an SRAM, the storage element is a  flip-flop.

A comparison of SRAM and DRAM is as shown:

PLD’s (Programmable Logic Devices) are the circuits that contain an array of AND gates and another array of OR gates. There are three kinds of PLD’s depending upon the type of array, i.e.

• Programmable Read-Only Memory
• Programmable Array Logic
• Programmable Logic Array (PLA)

• ROM is a memory device that stores the binary information permanently.

Programmable Logic Arrays (PLA’s) implement two-level combination logic in sum-of-products (SOP) form.

PLA’s are Programmable AND array followed by Programmable OR array as shown:

PAL: Programmable AND array followed by fixed OR array

PROM:

• It is known as programmable read-only memory
• It includes both AND array & OR array
• Out of these two arrays AND array is fixed and OR array is programmable.

Concept:

1 kB = 1024 bytes

One memory location of computer occupies 1 byte of memory.

So, to occupy 32 k of memory = 32 × 1024 = 32768 bytes are required.

∵ 1 byte = 1 memory location

∴ 32 k memory unit of computer will require 32768 memory locations.

Explanation: 

Programmable logic array (PLA):

It is a kind of PLD (Programmable logic device) used to implement a combinational logic circuit.

1.It has a set of programmable AND gate planes which link a set of programmable OR gate planes.

Hence option (2) is the correct answer.

2.It has 2N AND Gate for N-input variable and form or Gates it has m output.

PLA Design:

The memory IC used in a digital system is selected or enabled only for the range of address assigned to it and this process is called memory decoding.

It denotes the memory to be selected for a specific address.

Important Points

PLD’s (Programmable Logic Devices) are the circuits that contain an array of AND gates and another array of OR gates. There are three kinds of PLD’s depending upon the type of array, i.e.

• Programmable Read-Only Memory
• Programmable Array Logic
• Programmable Logic Array (PLA)

• ROM is a memory device that stores the binary information permanently.

PROM:

• It is known as programmable read-only memory
• It includes both AND array & OR array

Out of these two arrays AND array is fixed and OR array is programmable.

​​PAL: 

​Programmable AND array followed by fixed OR array