DDR SDRAMs
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DDR - SDRAMs are classified into different types including SDRAM, DDR1, DDR2, DDR3, and DDR4. SDRAM synchronizes itself with the CPU timing to allow for faster memory access. DDR1 allows for higher transfer rates through double pumping of the data bus. DDR2 further increases speeds through lower power usage and internal clock running at half the external clock rate. DDR3 and DDR4 continue to improve speeds and bandwidth through higher data transfer rates and lower voltage requirements. Each new generation is not compatible with previous types due to changes in signaling and interfaces.
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DDR SDRAMs
- 1. DDR - SDRAMs MADE BY : PRANKIT MISHRA (141CC00007) UNDER THE GUIDANCE OF : MR. NISHANT MATHUR(FACULTY INCHARGE) 1
- 2. Content •RAM •CLASSIFICATION OF DRAMS •SDRAM •TYPES OF SDRAM •DDR 1 •DDR 2 •DDR 3 •DDR 4 •COMPARISION BETWEEN SDRAM •REFERENCES 2
- 3. RAM •RAM is an acronym for random access memory, a type of computer memory that can be accessed randomly; that is, any byte of memory can be accessed without touching the preceding bytes. •RAM is the most common type of memory found in computers and laptops. •The two types of RAM differ in the technology they use to hold data, with DRAM being the more common type. In terms of speed, SRAM is faster. •DRAM needs to be refreshed thousands of times per second while SRAM does not need to be refreshed, which is what makes it faster than DRAM. 3
- 5. SDRAM •It stands for Synchronous Dynamic Random Access Memory. "Synchronous" tells about the behaviour of the DRAM type. •In late 1996, SDRAM began to appear in systems. •Unlike previous technologies, SDRAM is designed to synchronize itself with the timing of the CPU. This enables the memory controller to know the exact clock cycle when the requested data will be ready, so the CPU no longer has to wait between memory accesses. •SDRAM have to wait for the completion of the previous command to be able to do another read/write operation. 5
- 7. DDR 1 •Double data rate synchronous dynamic random-access memory (DDR SDRAM) is a class of memory integrated circuits used in computers. •Compared to single data rate (SDR) SDRAM, the DDR SDRAM interface makes higher transfer rates possible by more strict control of the timing of the electrical data and clock signals. Implementations often have to use schemes such as phase-locked loops and self-calibration to reach the required timing accuracy. •With data being transferred 64 bits at a time, DDR SDRAM gives a transfer rate of (memory bus clock rate) × 2 (for dual rate) × 64 (number of bits transferred) / 8 (number of bits/byte). Thus, with a bus frequency of 100 MHz, DDR SDRAM gives a maximum transfer rate of 1600 MB/s. •"Beginning in 1996 and concluding in June 2000, JEDEC developed the DDR (Double Data Rate) SDRAM specification (JESD79)." JEDEC has set standards for data rates of DDR SDRAM, divided into two parts. The first specification is for memory chips, and the second is for memory modules. 7
- 8. DDR 2 •DDR2 SDRAM is a double data rate synchronous dynamic random-access memory interface. •DDR2 was introduced in the second quarter of 2003 at two initial clock rates: 200 MHz (referred to as PC2-3200) and 266 MHz (PC2-4200). •It superseded the original DDR SDRAM specification, and is superseded by DDR3 SDRAM (launched in 2007). •DDR2 DIMMs are neither forward compatible with DDR3 nor backward compatible with DDR. •In addition to double pumping the data bus as in DDR SDRAM (transferring data on the rising and falling edges of the bus clock signal), DDR2 allows higher bus speed and requires lower power by running the internal clock at half the speed of the data bus. •The two factors combine to produce a total of four data transfers per internal clock cycle. •Since the DDR2 internal clock runs at half the DDR external clock rate, DDR2 memory operating at the same external data bus clock rate as DDR results in DDR2 being able to provide the same bandwidth but with higher latency. 8
- 9. DDR 3 •Double data rate type three SDRAM (DDR3 SDRAM) is a type of synchronous dynamic random-access memory (SDRAM) with a high bandwidth ("double data rate") interface, and has been in use since 2007. •It is the higher-speed successor to DDR and DDR2 and predecessor to DDR4 synchronous dynamic random-access memory (SDRAM) chips. •DDR3 SDRAM is neither forward nor backward compatible with any earlier type of random- access memory (RAM) because of different signalling voltages, timings, and other factors. •The primary benefit of DDR3 SDRAM over its immediate predecessor, DDR2 SDRAM, is its ability to transfer data at twice the rate (eight times the speed of its internal memory arrays), enabling higher bandwidth or peak data rates. •Compared to DDR2 memory, DDR3 memory uses less power. 9
- 10. DDR 4 •In computing, DDR4 SDRAM, an abbreviation for double data rate fourth-generation synchronous dynamic random-access memory, is a type of synchronous dynamic random- access memory (SDRAM) with a high bandwidth ("double data rate") interface. •Released to the market in 2014, it is one of the latest variants of dynamic random-access memory (DRAM), some of which have been in use since the early 1970s, and a higher-speed successor to the DDR2 and DDR3 technologies. •DDR4 is not compatible with any earlier type of random-access memory (RAM) due to different signalling voltages, physical interface and other factors. •The primary advantages of DDR4 over its predecessor, DDR3, include higher module density and lower voltage requirements, coupled with higher data rate transfer speeds. The DDR4 standard theoretically allows for DIMMs of up to 512 GiB in capacity, compared to DDR3's theoretical maximum of 128 GiB per DIMM. 10
- 13. THANK YOU 13