DRAM refresh requirement (2118 device): All rows in a 2118 dynamic RAM must be refreshed ________.

Introduction / Context:
DRAM cells store charge on tiny capacitors that leak over time. To preserve data, each row must be periodically refreshed by re-reading and re-writing it within a device-specified refresh interval. Classical 16K × 1 devices like the 2118 provide a representative requirement.

Given Data / Assumptions:

• Device: 2118 DRAM (16K × 1 organization, classic generation).
• Refresh is row-based and must complete within a fixed window.
• We assume nominal operating conditions.

Concept / Approach:
Historical DRAMs often require that all rows be refreshed within approximately 2 ms (some families use 4 ms or similar, but the 2 ms figure is typical for this class). Controllers satisfy this by distributing refresh cycles across time, ensuring that each row is accessed before its charge decays below a safe threshold.

Step-by-Step Solution:

Verification / Alternative check:
Datasheets specify maximum refresh interval per row set; meeting or beating that interval guarantees retention across the array.

Why Other Options Are Wrong:

Common Pitfalls:
Assuming refresh is optional; if missed, data corruption is inevitable in DRAM.

Final Answer:
every 2 milliseconds