Address multiplexing in DRAM — primary benefit What is the principal advantage of using multiplexed row/column addresses with DRAM memory devices?

Introduction / Context:
Most DRAMs use multiplexed addressing: the row address is presented first (latched by RAS), followed by the column address (latched by CAS). This technique enables large arrays with fewer external pins, which impacts cost and board routing complexity.

Given Data / Assumptions:

• Row/column multiplexing means the same physical pins carry row and column bits at different times.
• Pin count is a major constraint in IC packaging and PCB layout.
• Refresh behavior is independent of address multiplexing.

Concept / Approach:

Without multiplexing, a 16-bit address would require 16 dedicated pins. With multiplexing, only 8 address pins are needed (plus RAS/CAS control), cutting the pin count roughly in half for the same address width. This directly reduces package size and cost, and simplifies routing.

Step-by-Step Solution:

Verification / Alternative check:

DRAM datasheets list address pins as A0–Ax with RAS/CAS timing to latch row then column; SRAMs typically use non-multiplexed addresses and therefore more pins for comparable depth.

Why Other Options Are Wrong:

• Access time: mostly determined by internal cell/array timing, not pin multiplexing.
• Refresh requirement: unaffected by multiplexing; refresh is needed regardless.
• Chip-select elimination: DRAMs still use one or more chip-select/enable signals; multiplexing does not remove that need.

Common Pitfalls:

• Assuming multiplexing speeds the memory; it is primarily a packaging/routing optimization.

Final Answer:

reduced pin count and decrease in package size