The invention relates to memory modules and the formation of memory modules for a computer system.
Memory requirements of computer systems are increasing day by day. In order to get higher memory densities a possibility is to place a higher number of memory chips, for example chips with dynamic random access memory (DRAM) on a pc-board. DRAM is a type of random access memory that stores each bit of data in a separate capacitor. Due to standards, the physical space in computer systems is limited. So in order to place a higher number of DRAMs, they have to be stacked or placed on separate pc-boards attached to the main pc-board (motherboard). However, stacking DRAMs is expensive and it is difficult to manufacture separate pc-boards and using flexible cables to connect them.
In accordance with a first embodiment of the present invention, a memory module comprises a first pc-board with a first plurality of memory chips assembled thereon and with a first connector placed on a surface of the first pc-board, and a second pc-board with a second plurality of memory chips assembled thereon and with a second connector placed on the surface of the second pc-board, where the first and the second connector are electrically and mechanically connected. An advantage of an embodiment of this present invention is that it is easy to manufacture such memory modules, since connectors are easily placed on surfaces of pc-boards, for example, by using surface mountable connectors (SMT connectors).
In another embodiment of the present invention, the connector is placed between two rows of DRAMs or more. Such placement of the connection in this manner provides several advantages compared to the placement on the bottom edge side of such pc-board. For example, it is possible to use standard topology for data bus and pre-register command and address bus (C/A bus). Furthermore, it is possible to reduce the total data bus (DQ) and pre-register C/A capacitor nets and to reduce the number of stub resistors by half. So the costs for such pc-boards (which are also called dual inline memory modules (DIMM)) is reduced.
In a further embodiment of the present invention, more than two pc-boards are connected via connectors that are situated on surfaces of the pc-board. With this technique it is possible to build memory modules, which need only a limited amount of physical space but have an enhanced memory capacity.
In another embodiment of the invention, two pc-boards with memory chips assembled thereon are connected and placed in parallel, so that only a limited amount of physical space is used inside a computer system.
A further advantage of an embodiment of the present invention is to build the connectors on the pc-boards by connector parts that are arranged in such a way, that contacts of an edge connector of the first pc-board are arranged correspondingly. With this arrangement it is possible to keep the distances between the contacts of the edge connector to the contacts of the connectors as short as possible, thereby reducing additional resistances and residual capacities. A further advantage of the present invention is that only one edge connector is used by a memory module comprising two or more pc-boards with memory chips so that only one socket of the motherboard of the computer system is occupied after inserting such a memory module.
The above and still further features and advantages of the present invention will become apparent upon consideration of the following detailed description of specific embodiments thereof, particularly when taken in conjunction with the accompanying drawings wherein like reference numerals in the various figures are utilized to designate like components.
a schematically depicts two pc-boards with connectors in a view seeing assembled surfaces of the pc-boards before connecting them in a first embodiment of the invention.
b schematically depicts a side view of a memory module of two pc-boards, assembled with memory chips, which are connected in the first embodiment of the invention.
a schematically depicts two assembled pc-boards with connectors showing the surfaces of the pc-boards before connecting them together in a second embodiment of the invention.
b schematically depicts a side view of a memory module of two connected pc-boards in the second embodiment of the invention.
a schematically depicts three pc-boards before being connected in a third embodiment of the invention.
b schematically depicts a side view of a memory module of three pc-boards being connected in the third embodiment of the invention.
a schematically depicts three pc-boards before being connected in a fourth embodiment of the invention.
b schematically depicts a side view of a memory module of three pc-boards being connected in the fourth embodiment of the invention.
a depicts a data(DQ)-bus topology for connecting the memory chips of a DIMM while using the connectors at one side of the DIMM in accordance with the invention.
b depicts a Pre-Register C/A-Bus topology for connecting the registers in an embodiment with a connector at one side of the DIMM in accordance with the invention.
a depicts a data(DQ)-bus topology for connecting the memory chips of a DIMM in an embodiment with a connector between two rows in a DIMM in accordance with the invention.
b depicts a Pre-Register C/A-Bus topology for connecting registers of a DIMM in an embodiment with a connector between two rows of memory chips in accordance with the invention.
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The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appending claims rather than by the foregoing description and all changes with come within the meaning and the range of equivalency of the claims are therefore intended to be embraced therein.
In particular, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof. Accordingly, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.