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Memory subsystem technology and design for the z990 eServer

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5 Author(s)
Purdy, A.S. ; IBM Systems and Technology Group, 2455 South Road, Poughkeepsie, New York 12601, USA ; Swietek, D.J. ; LaPietra, F. ; Gower, K.C.
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This paper discusses the technology and design of the first double data rate (DDR) memory subsystem for the IBM zSeries® eServer™. The main storage subsystem accommodates the frequency mismatch between the memory controller and industry-standard synchronous dynamic random-access memory (SDRAM), protects data through error-correction code and SDRAM sparing, and increases overall memory subsystem bandwidth. Each memory card consists of the first synchronous memory interface (SMI) application-specific integrated circuit (ASIC) that is optimized specifically for DDR applications, the SMI-enhanced (SMI-E). The SMI-E controller data interface communicates with the high-speed memory controller on the multichip module through special phase alignment and elastic buffering circuitry that determines the optimal sampling point to reliably receive data from the controller. The SMI-E memory data interface is connected to registered DDR dual inline memory modules running up to 250 Mb/s using 256-Mb and 512-Mb SDRAM technology, thereby allowing memory card densities between 4 GB and 32 GB per card. Because of the increased DDR memory interface bit rates, special attention was paid to the design of the SMI-E substrate and base card to minimize noise. The memory, when used in a fully populated system, has four times more storage capacity than the previous z900 generation.

Note: The Institute of Electrical and Electronics Engineers, Incorporated is distributing this Article with permission of the International Business Machines Corporation (IBM) who is the exclusive owner. The recipient of this Article may not assign, sublicense, lease, rent or otherwise transfer, reproduce, prepare derivative works, publicly display or perform, or distribute the Article.  

Published in:

IBM Journal of Research and Development  (Volume:48 ,  Issue: 3.4 )

Date of Publication:

May 2004

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