DRAM memory works by storing bits of data in a capacitor inside an integrated circuit. It requires periodic refreshing (unlike SRAM) to keep data because its capacitors slowly release energy. DRAM is cheaper than SRAM and can store more data. However, DRAM-based components take longer to access data than SRAM-based ones and use more power.
DRAM in RAM Kits
SDRAM aka SDR SDRAM (synchronous dynamic RAM aka single data rate synchronous dynamic RAM) - A more advanced type of DRAM. SDRAM doesn’t react to data input until a CPU clock tells it to; it’s built to work in tandem with the CPU at its optimized clock speed. As such, SDRAM can perform more tasks simultaneously than a plain (asynchronous) DRAM.
DDR SDRAM (double data rate synchronous dynamic RAM) - DDR SDRAM is the next generation of SDRAM and the type of RAM people typically buy to upgrade or build a PC. As its name implies, DDR SDRAM can access data twice as fast as SDR SDRAM. DDR SDRAM also consumes less power than SDR SDRAM.
Newer versions of DDR SDRAM have a number after DDR (ex: DDR2 SDRAM). The higher the number, the better (they’re all better than DDR SDRAM).
- DDR2 SDRAM - Faster than DDR SDRAM.
- DDR3 SDRAM - Better performance and more memory than DDR2 SDRAM
- DDR4 SDRAM - Faster, better performance, more memory and consumes less power than DDR3 SDRAM.
DDR5 isn't supported by any CPU or motherboard yet, but that should change with the release of Intel's 12th Generation Alder Lake CPUs. Intel hasn't confirmed a release date, but the chips are expected in late 2021 or early 2022. Despite a lack of support, the first DDR5 RAM kit hit online retailers this week.
Note, when buying a RAM, it usually won’t say “SDRAM” after the “DDR” part.
DRAM in GPUs
GDDR SDRAM (graphics double data rate synchronous dynamic RAM, commonly referred to as GDDR) - This targets video graphics, and most modern GPUs can access it. GDDR SDRAM differs from DDR SDRAM in that it prioritizes processing more data, rather than latency.
GDDR SDRAM is available in different generations. In order from worst to best performance they are: GDDR, GDDR2, GDDR3, GDDR4, GDDR5, GDDR5X and GDDR6. The first GDDR6 consumer graphics cards are Nvidia’s Turing architecture cards, including the GeForce RTX 2080 Ti, GeForce RTX 2080 and GeForce RTX 2070.
This article is part of the Tom's Hardware Glossary.