Dynamic random access memory (DRAM)

Definition

Dynamic random access memory (DRAM) is a type of volatile memory that stores each bit of data in a separate capacitor within an integrated circuit. It is widely used in computer systems as the main memory because of its ability to provide fast read and write operations, albeit requiring periodic refreshing to maintain the stored data. DRAM's structure allows for a high density of memory cells, making it a cost-effective solution for meeting the demands of modern computing.

5 Must Know Facts For Your Next Test

1. DRAM is slower than SRAM but provides greater storage capacity at a lower cost, making it suitable for primary system memory.
2. Each DRAM cell consists of one transistor and one capacitor, requiring constant refreshing to ensure data integrity due to the gradual discharge of capacitors.
3. The development of DDR (Double Data Rate) DRAM has significantly improved performance by allowing data transfers on both the rising and falling edges of the clock signal.
4. While DRAM is essential for system performance, its design can lead to increased latency compared to other memory types due to the refresh cycles.
5. The evolution from conventional DRAM to variations like SDRAM and DDR has been crucial in adapting to the increasing demands of applications and operating systems.

Review Questions

• How does the structure of DRAM contribute to its functionality as a primary memory in computing systems?
  • The structure of DRAM, which consists of individual cells made up of a transistor and a capacitor, allows for a high density of memory storage. This enables DRAM to pack more bits into a smaller physical space, making it cost-effective as primary memory. However, because each cell needs constant refreshing to maintain its data due to capacitor leakage, this architecture introduces some latency in read and write operations compared to other types of memory.
• Evaluate the trade-offs between using DRAM versus SRAM in computer systems, particularly regarding speed, cost, and capacity.
  • When evaluating DRAM against SRAM, there are clear trade-offs. DRAM is slower than SRAM but offers a much higher density and lower cost per bit, making it ideal for large-scale memory applications like main system RAM. On the other hand, SRAM provides faster access speeds and does not require refreshing, but it is more expensive and has a lower storage capacity. As a result, many systems use both types strategically: SRAM for cache memory where speed is crucial, and DRAM for main memory where larger capacities are necessary.
• Analyze the impact of DRAM refresh cycles on system performance and how innovations like DDR technology address these challenges.
  • The necessity for DRAM refresh cycles can negatively impact system performance because these cycles consume time that could otherwise be spent on active read or write operations. This adds latency that can slow down overall system performance. Innovations like DDR technology help mitigate these challenges by allowing data transfers on both clock edges, effectively doubling the data throughput without increasing clock frequency. This advancement not only boosts performance but also makes better use of available memory bandwidth despite the inherent limitations posed by DRAM's refresh requirements.

Related terms

Volatile Memory: A type of computer memory that requires power to maintain the stored information, meaning data is lost when power is turned off.

Static Random Access Memory (SRAM): A type of non-volatile memory that uses bistable latching circuitry to store each bit, offering faster access speeds compared to DRAM but at a higher cost and lower density.

Memory Refresh: The process in DRAM where the stored data is periodically read and rewritten to prevent data loss due to capacitor leakage.