related document
SDRAM
What is Synchronous DRAM (SDRAM)?
- Conventional DRAM is operated by a separate controller that is independent from computer system operation, which makes it difficult to keep pace with the advancement of higher speed CPUs. However, synchronous DRAM is designed to process data at the same speed as the system clock (time controller which generates periodic signals) that controls the CPU. Therefore, synchronous DRAM is regarded as the core component that is advantageous for high speed processing of large volume data.3
- SDRAM was developed immediately after EDO generation products. It is a breakthrough in that it synchronizes the frequency to the system clock that controls CPU. Synchronization of CPU and frequency minimizes time delays and facilitates memory retrieving process.
- SDRAM has been used for PC, server and network, and now its usage is expanding to various consumer electronics such as printer, DSC, HDD and STB.
SDRAM Application
| Density | Application |
|---|---|
| 16Mb | HDD | ODD |
| 64Mb | HDD | LCD TV | ODD / PDP | STB |
| 128Mb | HDD | Network | Printer | STB |
| 256Mb | D-TV | Desktop PC | DSC / DVD | Network | Note PC | Printer | Router | Server | Storage | STB | Telecom |
| 512Mb | Network | Printer | Router | Server | STB |
Comparison of SDRAM and DDR/DDR2 SDRAM
Key Feature
| SDRAM | DDR | DDR2 | |
|---|---|---|---|
| Vdd/Vddq | 3.3V | 2.5V | 1.8V |
| Package | 54 TSOP-II | 66 TSOP-II | 60/84 BGA |
| 60 BGA | |||
| Bit Org. | x4, x8, x16 | ||
| Clock Freq | ~167 Mhz | 100~200 Mhz | 200~400 Mhz |
| Data rate | ~167 Mtps | 200~400 Mtps | 400~800 Mtps |
| Interface | LVTTL | SSTL_2 | SSTL_18 |
| Prefetch | N/A | 2 | 4 |
| Burst Length | 1, 2, 4, 8, F/P | 2,4,8 | 4,8 |
| Strobe | No | Yes | Yes |
Typical Memory Sub-System with SDRAM
- 64bit wide bus
- LVCMOS(3.3V)
- Data In/Out at clock high-going edge
