High capacity memory system with improved command-address and chip-select signaling mode
First Claim
1. A buffer device for operation on a memory module, the buffer device comprising:
- a chip select (CS) decoder; and
a modal register to store a value indicative of one of at least two modes of operation, wherein,in a first mode of operation, the buffer device drives a chip select signal group received on a primary-side CS interface onto a corresponding secondary-side CS interface;
in a second mode of operation, the CS decoder decodes a CS signal group received on the primary-side CS interface to create signals for the secondary-side CS interface;
in the first mode of operation, the buffer device drives an on-die termination (ODT) signal received on a primary-side ODT line onto a corresponding secondary ODT line; and
in the second mode, the buffer device, based at least in part on an output of the CS decoder, generates an ODT signal to transmit on the secondary ODT line.
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Accused Products
Abstract
A memory controller and buffers on memory modules each operate in two modes, depending on the type of mother-board through which the controller and modules are connected. In a first mode, the controller transmits decoded chip-select signals independently to each module, and the motherboard data channel uses multi-drop connections to each module. In a second mode, the motherboard has point-to-point data channel and command address connections to each of the memory modules, and the controller transmits a fully encoded chip-select signal group to each module. The buffers operate modally to correctly select ranks or partial ranks of memory devices on one or more modules for each transaction, depending on the mode.
24 Citations
19 Claims
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1. A buffer device for operation on a memory module, the buffer device comprising:
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a chip select (CS) decoder; and a modal register to store a value indicative of one of at least two modes of operation, wherein, in a first mode of operation, the buffer device drives a chip select signal group received on a primary-side CS interface onto a corresponding secondary-side CS interface; in a second mode of operation, the CS decoder decodes a CS signal group received on the primary-side CS interface to create signals for the secondary-side CS interface; in the first mode of operation, the buffer device drives an on-die termination (ODT) signal received on a primary-side ODT line onto a corresponding secondary ODT line; and in the second mode, the buffer device, based at least in part on an output of the CS decoder, generates an ODT signal to transmit on the secondary ODT line. - View Dependent Claims (2, 3, 4)
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5. A buffer device for operation on a multi-rank, multi-device-site-per-rank memory module, the buffer device comprising:
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a chip select (CS) decoder; and a secondary-side CS interface having multiple CS signal outputs for each memory module rank, the buffer device capable of using the CS signal outputs to independently select different subgroups of device sites that are each less than a half rank of device sites, and wherein, in a first mode, the buffer device receives a chip select (CS) signal group, and asserts multiple corresponding ones of the multiple CS signal outputs on the secondary-side CS interface to select multiple subgroups of device sites to provide a corresponding full rank selection; and in a second mode, the buffer device receives a fully encoded CS signal group, the CS decoder decodes the encoded CS signal group to determine one or more of the subgroups of device sites to select, and the buffer device asserts at least one of the multiple CS signal outputs on the secondary-side CS interface to provide a corresponding partial rank selection. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. An apparatus comprising:
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a memory controller comprising a modal register to store a value indicative of at least two modes of operation, wherein, in a first mode, the controller asserts a first decoded chip select (CS) output to select multiple subgroups of device sites on one of a plurality of memory modules to provide a corresponding full rank selection; and in a second mode, the controller drives a fully encoded CS signal group output to each of the plurality of memory modules, the fully encoded CS signal group output identifying one or more of the subgroups of device sites to select to provide a corresponding partial rank selection. - View Dependent Claims (17, 18, 19)
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Specification