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Dual Port DDR SDRAM

Discussion in 'Electronic Design' started by yy7d6, Jul 24, 2006.

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  1. yy7d6

    yy7d6 Guest

    Hi
    Any knows of a Dual Port DDR SDRAM device?
    Device that has seperate Read/Write address.

    Thanks.
     
  2. Nico Coesel

    Nico Coesel Guest

    I've never came across it. Given the principles of DRAM I doubt it
    exists. What is your bandwidth requirement?
     
  3. Guest

    Highly unlikely, there used to be a chip that would turn a standard
    dram into dual port, went up to 1Mbyte IIRC. At least 10 years ago so
    probably long obsolete.
     
  4. This is being done quite a lot on graphic cards, where the graphic chipset
    itself (or in some cases a programmable gate array), is used to provide
    such access. The problem of course is that most DDR memories are 'burst'
    orientated devices, so the external buffer needs to be large enough to
    support a full burst. Also the complexity is very different for a
    sequential burst orientated read access (as needed on a video card),
    versus a generic read. A lot will depend on what speeds are needed, and
    the nature of the expected I/O. Some video DRAM's, offer the ability to
    have two pages (or more) open at once, to simulate dual port operations.
    Cypress do an interconnect family, to allow dual port access on a variety
    of memories. A search for 'FullFlex' devices, may provide what is needed.

    Best Wishes
     

  5. How about doing the old fashioned way with interleaved memory? Vital
    Industries did the a long time ago with slow 1K * 4 DRAM in their
    Squeeze Zoom digital video effects generator for live manipulation of
    broadcast quality video. By careful timing and using two pages of video
    ram it allowed one page to be updated while the second page was being
    displayed live.

    It was the first effective DVE system on the US market, but
    apparently long gone from any broadcast use because of the cost to keep
    it hot and running.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
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