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High-Speed DRAMs: A Roadmap

This article provides an introduction to high-speed DRAMs, including fast DRAMs using multi-banks, graphics DRAMs, and pseudo-SRAMs. It discusses the different types of DRAMs and their applications, as well as the evolution of high-speed DRAM interfaces. The article emphasizes the need for reducing latency and increasing speed in memory systems.

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High-Speed DRAMs: A Roadmap

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  1. App. Specific DRAMs Eyad Al-Hazmi

  2. Roadmap • Introduction • High-Speed DRAMs • Fast DRAMs using Multi Banks • Graphics DRAMs • Pseudo-SRAMs

  3. Introduction • DRAM, Dynamic Random Access Memory • Historically been high volume, standard memory • Many DRAM applications differing in requirements • Many types of DRAMs

  4. High-Speed DRAMs • DRAMs were asynchronous with processor .... • Sometimes processor access while refreshing • Processor has to wait for interrupt req. from memory TOTAL WASTE OF TIME !!! • Examples: FPM DRAM

  5. High-Speed DRAMs Cont. • A synchronous interface was added to DRAM • DRAM is under system clock control • Permits adding control features behind it • Made a huge improvement in speed • Examples: SDRAM (speed = 133 MHz, Operating voltage = 3.3 V)

  6. High-Speed DRAMs Cont.

  7. High-Speed DRAMs Cont. • A DDR interface was added to DRAM • Allowing of fetching two words per one cycle • Data rate = 2*Clock frequency • Examples: DDR SDRAM, DDRII SDRAM

  8. High-Speed DRAMs Cont.

  9. Fast DRAMs using Multi-Banks • Reduces the capacitance of word lines • Two Designs; Different characteristics • Goal: Reduction of Read Latency

  10. CS CS R/W R/W R/W CS Address Address . . . Address Data Data m m Data . . Data width = m × p bits Fast DRAMs using Multi-Banks Cont.

  11. CS CS R/W R/W R/W Address Address Data Data m m m m Fast DRAMs using Multi-Banks Cont. n+k k k to 2k decoder Address n . . . CS . . . Address Data Data width = m bits

  12. Graphics DRAM (VRAM) • Requirements: • Lower memory system density • Higher speed than main memory applications • Wide I/O bus to match system bus • Need for few DRAMs  DRAMs can be closer • Uses point-to-point interface to increase I/O speed

  13. Pseudo-SRAM (PSRAM) • DRAM inside – SRAM outside (SRAM Interface) • DRAMs with SRAM interfaces first appeared in 1980s • High density and power requirements, motivation to • make newer SRAM interface DRAMs, beginning of • PSRAMs.

  14. Summery • Introduction • High-Speed DRAMs • Fast DRAMs using Multi Banks • Graphics DRAMs • Pseudo-SRAMs

  15. Thank You...

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