What is SDRAM (Synchronous Dynamic Random-Access Memory) ?
SDRAM (Synchronous Dynamic Random-Access Memory) is a type of DRAM (Dynamic RAM) that is synchronized with the system bus (the CPU clock). This synchronization allows SDRAM to operate more efficiently by aligning with the CPU’s timing, which reduces latency and improves performance over older asynchronous DRAM.
Key Features of SDRAM:
- Synchronous Operation: It works in lockstep with the CPU clock, allowing it to predict and prepare for read/write operations.
- Pipelining: SDRAM supports pipelining, meaning it can accept a new command before the previous one finishes, improving throughput.
- Volatile Memory: Like all DRAM, it loses data when the power is turned off.
- Still Needs Refreshing: Data in SDRAM cells must be refreshed thousands of times per second.
Evolution of SDRAM:
SDRAM was first used in the late 1990s and has evolved into more advanced forms, known as DDR SDRAM (Double Data Rate SDRAM):
- DDR (DDR1)
- DDR2
- DDR3
- DDR4
- DDR5 (latest as of 2024)
Each generation offers faster speeds, lower power consumption, and greater bandwidth.
Summary:
| Type | Sync with CPU | Pipelining | Used in |
|---|---|---|---|
| DRAM | No | No | Early computers |
| SDRAM | Yes | Yes | PCs (late ’90s) |
| DDR SDRAM | Yes | Yes | Modern PCs |