Offset basecard

Abstract: In an adapter card having an attached daughter card (304), the adapter card is offset from its edge connector (106), such that the edge connector (106) occupies one plane and the base card (104) occupies a parallel plane, thereby allowing the daughter card (304) to attach to the base card (104) and occupy the same plane as the edge connector (106) which allows the daughter card (304) to use an I/O connector without violating the space envelope of the next base card (104), and also allows a daughter card (304) to be interchanged between systems with different packaging architectures.

Description: The present invention relates to a printed circuit card for a computer system. In particular, the present invention relates to a printed circuit card which can attach to a daughter card designed for a system with a different architecture, and which can attach to a daughter card with an integral I/O connector without violating the space envelope of any adjacent printed circuit card. In a typical computer system, printed circuit cards are used to carry the bulk of the electronic circuitry. A common design has a large printed circuit card carrying the circuitry for operating the basic functions of the computer. This large printed circuit card will be referred to hereinafter as a mother board. In addition the basic functions of the computer, which are performed by the circuitry on the mother board, a number of other functions have been developed to perform specific tasks for a computer user. For example, large data storage requirements have been satisfied through the use of storage devices such as magnetic disk devices and optical disc storage devices, and a variety of printing devices have been developed to support the requirement for printed output. The wide variety of input/output (I/O) devices available each have specific electronic circuitry requirements to allow the computer to control the operation of, and interface with, the I/O device. Since the particular work a computer is used for will dictate the types of required I/O devices, it is economically inefficient to include circuitry as a standard feature on the mother board which supports a specific type of I/O device or a specific optional function. Recognition of this inefficiency led to the development of printed circuit base adapter cards (hereinafter referred to as base cards). Base cards are printed circuit boards which are designed to hold electronic circuitry required to perform a specific function, such as controlling a printer or storage device and interfacing that device with the mother board, or any other desired function. The specific function performed is not important for the purposes of this disclosure. The advantage of using base cards is that it requires the cost of circuitry to be incurred only when it is required to support a specific function. Base cards typically have edge connectors with electrical contacts which can be plugged into a connector on the mother board, thereby adding the base card circuitry to the circuitry on the mother board. In addition, base cards which connect to I/O devices usually have an I/O connector on an edge of the board which allows a cable to be connected between the I/O device and the base card. In a typical micro-computer, the mother board has multiple connectors to attach to multiple base cards. While the plane of the base card is often perpendicular to the plane of the mother board, it is not required to be perpendicular, and may in fact be oriented at any angle convenient for packaging purposes. Over time, the types of functions performed by base cards have become increasingly complex, with a corresponding increase in circuit requirements. This has led, in turn, to the development of daughter cards. A daughter card is defined for the purposes of this disclosure as a printed circuit board with connects to a base card and adds circuitry to the base card in the same manner as the base card adds circuitry to the mother board. It is typically attached to the base card in a plane which is substantially parallel to the plane of the base card. Likewise, more than one type of daughter card may be designed for a base card, just as more than one type of base card may be designed for a mother board. DE-U-8308866 describes a base circuit card assembly comprising: a base circuit card; a daughter card releasably mounted on the base card in a plane parallel to the plane of the base card; an edge connector for electrically attaching the base card to the mother board; and a base card connector for electrically attaching the daughter card to the base card. The use of multiple base cards by a mother board has imposed space constraints. The space constraints result in a defined physical space envelope in which each base card may be placed. As a consequence, and an additional limitation on the location of the I/O connector is created which requires that the connector be attached to the base card. This is due to the thickness of the I/O connector which, if placed on the daughter card, would impinge on the space envelope of the next base card. The limitation on the location of the I/O connector requires the use of a connector which can be used by any of the daughter cards which might be connected to the base card. It is possible that each of the multiple optional daughter cards available for a given base card may have a different I/O connector requirement due to the number of connection lines required for the particular I/O device. This generally results in the selection of the I/O connector with the largest number of lines, and hence, the I/O connector with the highest cost. In addition to the added cost of daughter cards caused by the lack of flexibility in choice of connectors, another problem exists due to the normal evolution of system architecture which is even more costly. As each new generation of computers is developed to replace the previous generation, changes in physical packaging can prevent the use of daughter cards from being used in the new generation of computers. Likewise, daughter cards developed for the new generation of computer may not fit in older generation computers. This incompatibility causes several problems. Purchasers of computers with daughter cards have a significant investment in the cards. That investment may effect the ability of the purchaser to change to a new system if the cost of replacing the function provided by the daughter cards makes the change economically prohibitive. Likewise, a daughter card developed for another system architecture may be very desirable to a purchaser, but be economically prohibitive to use if the entire system must be changed due to incompatibility of the board with the purchaser's system. For similar reasons, incompatibility of daughter cards developed for systems of different architecture types causes problems for manufacturers as well as purchasers. A significant investment in daughter cards of one architecture type will discourage purchasers from investing in a different architecture type. In addition, manufacture of multiple daughter cards having the same function, but packaged for multiple architecture types, will increase manufacturing costs and increase inventory stocking problems. Thus, incompatibility caused by differences in packaging between different architecture types impairs the ability of computer purchasers to upgrade to new computers or to use functions developed for other architecture types. In addition, it also increases the cost of manufacturing daughter cards, and increases inventory costs. An aim of the present invention is to provide a base card having a connector for connecting to a daughter card without violating a physical space envelope of the base card. In accordance with the present invention, there is now provided a base circuit card assembly for mounting on a mother board, the assembly comprising: a base circuit card; a daughter card releasably mounted on the base card; an edge connector for electrically attaching the base card to the mother board; and a base card connector for electrically attaching the daughter card to the base card; characterised in that the assembly comprises: an offset connector disposed between the base card and the edge connector to offset the base card to one side of the edge connector, the position of the plane of the edge connector being determined by the thickness of the offset so that the daughter card is attached to the base card without violating the space envelope of the base card. In accordance with the present invention, there is further provided a method as defined in claim 6. In an example of the present invention to be described later, there is provided a base card having an offset edge connector, such that the edge connector occupies one plane and the base card occupies a parallel plane. The base card comprises an I/O connector designed for a specific daughter card. The base card enables daughter cards developed for one architecture type to be used in a system based on a different architecture type. An embodiment of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 is an isometric view of the base card with offset edge connector. Figure 2 is an end view of the base card looking into the plane of the board Figure 3 is a side view of a daughter card. Figure 4 is an edge view of a daughter card. Figure 5 is an isometric view of the base card with and attached daughter card. By way of general overview, the problems discussed above, relating to incompatibility of cards between differing architecture types and space envelope problems caused by placing I/O connectors on daughter cards, is overcome by modifying the base card on one of the system types such that a daughter card can fit within the space envelope of the base card. This is accomplished by offsetting the base card from its edge connector. By offsetting the base card, a daughter card designed for another architecture can fit in the packaging structure of the present system, thereby allowing migration of daughter cards between different packaging architecture types. In addition, the daughter card can have an integral I/O connector without violating the space envelope of the base card, thereby eliminating the need for a more expensive I/O connector on the base card. Figure 1 shows an embodiment of the base card 102. The printed circuit 104 is shown as a blank board for ease of illustration. The specific circuitry used on the base card 102 is not shown because it will vary depending on the type of I/O device or function and is not necessary to understanding the invention. Electrical connections 110 are shown to illustrate the location where the daughter card (shown in figures 3-5) would attach electrically to the base card 102 in the preferred embodiment. Those skilled in the art will realise that the location of the electrical connections 110 is an arbitrary design choice. In practice, a male or female connector can be attached to the printed circuit 104 via electrical connections 110 for mating with a female or male connector, respectively, on the daughter card (not shown). In addition, it is also possible to permanently attach the daughter card to the base card 102 via permanent electrical wire connection. However, detachable electrical connectors would be used in the preferred embodiment to facilitate ease of removal or substitution of the daughter card. The specific mating connectors used are a mere design choice based on the requirements of the particular circuit used by the printed circuit 104 and can be chosen from numerous commercially available connectors. As figure 1 shows, the edge connector 106 is separated from the printed circuit 104 by an offset 108. The edge connector 106 is shown to be in a substantially parallel plane with the printed circuit board 104 in the preferred embodiment. However, those skilled in the art will understand that the invention can be implemented with the plane of the printed circuit 104 at an angle to the plane of the edge connector 106. The specific offset distance provided by the offset 108 will be a design choice based on several factors, such as space envelope limitations, circuit component types, etc. In prior art adapter boards, well known in the art, the printed circuit 104 and the edge connector 106 would typically be a single element sharing the same plane. The preferred embodiment shown in figure 1 offsets the printed circuit 104 to allow use of the plane space above the edge connector 106 by a daughter card. The conductive pads 114 provide for electrical connection to the mother board (not shown) when inserted into a connector on the mother board. Lines 112 provide electrical connection between the edge connector and printed circuit 104. Lines 112 run through offset 108. Lines 112 connect to conductive pads 114 to provide signal paths between the mother board and printed circuit 104. The edge connector 106 is shown in two sections for illustrative purposes. However, mere design choices based on the particular mother board and base card in question will determine the actual configuration in practice. Figure 1 also shows support tab 116. Support tab 116 is inserted in supports commonly found in micro-computers to hold the end of a base card in place. This type of physical support method is well known in the art. As shown, the support tab 116 is offset the same distance as the edge connector 106. This allows the support tab 116 to be in the same plane as the edge connector 106, which in turn allows the base card 102 to be inserted in the micro-computer without relocating the supports. It will be understood by those skilled in the art that the support tab is an optional feature because the base card 102 for a particular function can be a short card which does not extend to the end of its board slot. Figure 2 shows an end view of the base card described above in the discussion of figure 1. In addition, mounting screws 202, which provide the physical connection of the edge connector 106, the printed circuit 104 and the offset 108 are shown. Those skilled in the art will recognise that many other attachment techniques are well known in the art. Support tab 116 is shown aligned in the same plane as the edge connector 106. Figure 3 shows a side view of a daughter card 302. The circuit components will vary for the same reasons that the circuit components on the printed circuit 104, discussed above, will vary and are, therefore, not shown. Daughter board 302 shows daughter circuit 304 which would, in practice, have the circuitry for the daughter card function mounted thereon. Mounting screws 306 show a typical method of physically attaching the daughter card 302 to the base card 102. It is understood that the actual method of physical attachment and the location of the attaching points are a mere design choice. At the left end of daughter card 302 is I/O connector 308. The particular I/O connector used will also vary based on the function of the daughter card 302. Figure 4 shows a top view of the daughter card 302. Mounting screws 306 are shown contained in spacers 402. I/O connector 308 is shown at the left end of daughter card 302. Electrical connections 404 are shown to illustrate one type of electrical connection for providing signal connection between the daughter card 302 and the base card 102. Figure 5 shows the position a daughter card 302 would occupy in relation to a printed circuit 104, and an edge connector 106 on a base card 102. As shown in the preferred embodiment, the daughter card 302 is generally within the plane occupied by the edge connector 106 and in a plane parallel to that occupied by the printed circuit 104. As a result of offsetting the base card 102, an I/O adapter 308 specifically designed to meet the requirements of the daughter card 302 can be directly attached to the daughter card 302 without violating the envelope space of the base card 102. As a result, the requirement for a general purpose I/O connector 308 on the base card 102 is eliminated, allowing the least cost I/O connector 308 to be selected for the base card 102 / daughter card 302 combination. In addition, the offset base card 102 allows more flexibility in physically locating a daughter card 302 in a space envelope. This allows daughter cards 302, which would not normally fit in a given packaging architecture to be used without modification. As a result, daughter cards can be migrated from one architecture type to another. While the invention has been particularly shown and described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes in detail may be made. For example, the plane used by the daughter card can vary from the plane used by the edge connector without violating the space envelope. Likewise, it is not critical that the base card plane and daughter card plane be parallel. Accordingly, the invention herein disclosed is to be limited only as specified in the following claims.

Claims: A base circuit card assembly for mounting on a mother board, the assembly comprising: a base circuit card (104); a daughter card (304) releasably mounted on the base card (104); an edge connector (106) for electrically attaching the base card to the mother board; and a base card connector (404) for electrically attaching the daughter card (304) to the base card (104); characterised in that the assembly comprises: an offset connector (108) disposed between the base card and the edge connector to offset the base card (104) to one side of the edge connector (106), the position of the plane of the edge connector (106) being determined by the thickness of the offset (108) so that the daughter card (304) is attached to the base card (104) without violating the space envelope of the base card (104). An assembly as claimed in claim 1, wherein the base circuit card (104) comprises an offset support tab (116) in a plane parallel to and towards one end of the base card (104). An assembly as claimed in claim 1, wherein the base card connector cooperates with a daughter card connector carried by the daughter card (304) to locate the daughter substantially in the same plane as the edge connector (106). An assembly as claimed in claim 1, wherein the daughter card (304) comprises at least one I/O connector (308) for electrically attaching the daughter card (304) to an I/O device. A computer system comprising a base circuit card assembly as claimed in any preceding claim. A method of attaching a daughter circuit card (304) to a base circuit card (104) without violating the space envelope of the base circuit card, comprising: separating an edge connector (106) from the base card (104); attaching an offset connector (108) between the edge connector and the base card; and attaching a daughter card (304) to the base card such that the daughter card occupies a plane substantially parallel to the base card, and the daughter card is within the plane occupied by the edge connector, the position of the plane of the edge connector being determined by the thickness of the offset connector. A method as claimed in claim 3, comprising attaching an I/O connector (308) to an edge of the daughter card (304), the I/O connector attached such that it is contained within the space envelope of the base card.

Inventors: HOOD ROBIN ALLEN, REISWIG JOHN WILLIAM, HOOD, ROBIN ALLEN, REISWIG, JOHN WILLIAM
Applicants: IBM, INTERNATIONAL BUSINESS MACHINES CORPORATION
Application year: 1990
Main classification: H05K7
IPC codes: H05K1, H05K7, G06F1