SSC IMD SA 2017 – Question 106

In the fabrication of which of the following components are bipolar devices desirable?

• Main memory
• Cache memory
• Microprogram memory
• Cache and microprogram memory

Detailed Explanation:

The correct answer is c) Microprogram memory (माइक्रोप्रोग्राम मेमोरी).

Key Concepts:

• Bipolar Devices: Fabricated using BJT (Bipolar Junction Transistors) or ECL (Emitter-Coupled Logic) technologies. They are characterized by very high switching speeds and low propagation delays, but have higher power consumption and lower integration density compared to MOS/CMOS circuits.
• Microprogram Memory (Control Store): In a microprogrammed control unit, the control store holds the micro-routines that decode and execute machine instructions. Because every CPU clock cycle relies directly on reading microinstructions from control memory, the access time of this memory must be exceptionally fast to prevent bottlenecks.
• Since microprogram memory is read-only during normal CPU execution and has a relatively small capacity compared to main memory, high-speed bipolar ROM/PROM devices are desirable for its implementation.
• Main memory requires ultra-high density and low power, making MOS DRAM the standard. Cache uses CMOS SRAM for balancing density, speed, and read/write capability.