System organization – can DRAM chips be combined to build larger capacity and wider word sizes using the same methods applied to other memory types?

Difficulty: Easy

Correct Answer: Correct

Explanation:


Introduction / Context:
Practical systems rarely use a single memory chip. Designers array multiple devices to meet total capacity and bus width targets. This question checks whether DRAM can be organized in banks and x-width groupings similarly to other memory families, acknowledging refresh considerations but focusing on organization principles.


Given Data / Assumptions:

  • Goal: increase total bytes and/or widen data bus (for example, from x8 devices to x64 bus).
  • Standard memory controllers handle DRAM timing, refresh, and chip select signals.
  • Comparable methods are used for SRAM/ROM arrays at the organization level.


Concept / Approach:
To widen the data path, place several x8 DRAMs in parallel (data lines aggregated) to create x16, x32, or x64 interfaces. To increase depth (capacity), use additional ranks/banks with separate chip selects or address multiplexing. These methods mirror how SRAM/ROM arrays are organized; the main difference is that DRAM requires periodic refresh and row/column multiplexed addressing, which the controller manages transparently.


Step-by-Step Solution:

1) Choose device width (e.g., x8) and count needed to match bus (e.g., 8 chips → x64).2) Tie corresponding address/control lines; route each chip to its data byte lane.3) Add chip selects/ranks to scale capacity beyond a single set.4) Use a controller to schedule refresh and command sequences (ACT, RD/WR, PRE).


Verification / Alternative check:
DIMMs combine many DRAM chips into modules presenting standard widths (x64 with ECC x72). Reference designs for microcontrollers show similar organization with smaller DRAMs.


Why Other Options Are Wrong:
Claiming SRAM-only is false; DRAM modules exemplify the method. Refresh cannot be disabled; it is handled, not avoided. ECC is optional and does not determine combinability.


Common Pitfalls:
Forgetting byte-lane routing and DQ/DQS alignment; overlooking rank address mapping; assuming DRAM’s need for refresh prevents standard width/capacity scaling—it does not.


Final Answer:
Correct

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