Address Bus and Memory Types

The address bus is used to communicate memory addresses between the CPU and the memory subsystem. The address bus is a collection of wires that transmit the address of the memory location being accessed. The size of the address bus determines the maximum amount of memory that can be addressed.

There are several types of memory in a computer system, and each has different characteristics. Some of these memories are directly connected to the address bus, while others are not.

Main Memory and Address Bus

Main memory is the primary memory of a computer system. It is used to store data and instructions that are currently being processed by the CPU. The main memory is connected to the address bus, and the size of the main memory is limited by the size of the address bus.

Onboard Memory and Address Bus

Onboard memory is the memory that is built into a device, such as a graphics card or a sound card. Onboard memory is not directly connected to the address bus, and it is not limited by the size of the address bus.

Cache Memory and Address Bus

Cache memory is a type of memory that is used to improve the performance of a computer system. Cache memory is located between the CPU and the main memory, and it stores frequently accessed data and instructions. Cache memory is not directly connected to the address bus, and it is not limited by the size of the address bus.

Secondary Memory and Address Bus

Secondary memory is a type of memory that is used to store data and instructions that are not currently being processed by the CPU. Secondary memory includes hard disk drives, solid-state drives, and optical drives. Secondary memory is not directly connected to the address bus, and it is not limited by the size of the address bus.

Answer

Based on the above explanation, the correct answer is option 'A', which is secondary memory. Secondary memory is not directly connected to the address bus and is not limited by the size of the address bus.