Abstract:
A first mother board among a plurality of mother boards is mounted adjacent to a reference mother board and a second mother board among said plurality of mother boards is mounted in a position rotated 180° about the horizontal centerline of the second mother board and mounted back to back to the first mother board, whereby the reference mother board and the first and second mother boards can be interconnected at a minimal distance.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to an arrangement for mounting mother boards in an electronic device such as a computer which requires high speed operation and high density mounting. More particularly, it is directed to a mounting structure for an electronic device where a plurality of identical mother boards are mounted and arranged in such a manner that they can be interconnected to a reference mother board with minimal cable length. 
     An example of a conventional mounting technology for electronic devices allowing their boards to be interconnected at a minimal distance is disclosed in Japanese Patent Laid-Open No. 60-98698. In this conventional technology the cases, each of which accommodates a mother board, i.e., a unit, are staggered in order to minimize the length of the cables interconnecting the mother boards. 
     SUMMARY OF THE INVENTION 
     The above-mentioned conventional technology is applicable only to a one-case to one-mother board, i.e., one-unit, configuration, and therefore does not address the attempt of minimizing the length of the cables interconnecting one reference mother board with a plurality of other mother boards. Therefore, there will be no advantage of reduced cable length but will be a disadvantage of increased number of cases, whereby it is not suitable for computers and other electronic devices which require high speed operation and high density mounting. 
     An object of this invention is to overcome the above problems and to thereby provide a mounting structure for electronic devices which is capable of minimizing not only the length of the cables interconnecting a reference mother board with a plurality of other mother boards but also both the surface area for mounting a case and the maintenance area. 
     According to this invention, the above object can be achieved by mounting a cable connector on a reference mother board adjacent to a plurality of other mother boards and the cable connectors on the plurality of other mother boards adjacent to the reference mother board. More specifically, in the case where the plurality of other mother boards, e.g., two mother boards, are to be mounted at a position nearest possible to the reference mother board, a plurality of other mother boards which are identical must be used to reduce the number of board types, and one of the other mother boards (first mother board) is mounted side by side with the reference mother board, while the other mother board (second mother board) is rotated 180° with the cable connector of the reference mother board as the center of rotation so that the second mother board is mounted on the back of the first mother board with its top and bottom inverted with respect to those of the first mother board. 
     To further reduce the cable length, the reference mother board may be mounted in a position so that its cable lengths to each of the other two mother boards are equal. 
     The high speed operation of the electronic device with minimized delay in signal transmission can be achieved by minimizing the cable lengths between the mother boards in the following manner. The cable connector for input/output (I/O) signals of the reference mother board is mounted in a position nearest possible to the other mother boards, while the cable connectors for I/O signals of the other mother boards are also mounted in positions nearest possible to the reference mother board. To mount the first mother board to the reference mother board, the first mother board is simply arranged side by side with the reference mother board; while to mount the second mother board near the reference mother board, the second mother board is rotated so that it is mounted on the back of the first mother board with its top and bottom being inverted with respect to those of the first mother board. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of an embodiment of this invention; 
     FIG. 2 is a front elevational view of the embodiment shown in FIG. 1; and 
     FIG. 3 is a plan view of another embodiment of this invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of the mounting structure for an electronic device according this invention will hereunder be described in detail with reference to the drawings. 
     FIG. 1 is a plan view of the embodiment of this invention; and FIG. 2 is a front elevational view of the embodiment shown in FIG. 1. With reference to FIGS. 1 and 2, a case la supports a reference mother board 2a. Similarly, a case 1b supports a first other mother board 2b and a second other mother board 2d. Mounted on the reference mother board 2a are a plurality of daughter boards 3a. Similarly, mounted on first and second other mother boards 2b, 2d are a plurality of daughter boards 3b, 3d. At each end of the reference mother board 2a are a plurality of cable connectors 4a. Similarly at each end of the first and second other mother boards 2b, 2d are a plurality of cable connectors 4b, 4d. In FIGS. 1 and 2, reference numeral 1a designates a case A; 1b, a case B; 2a, a reference mother board A; 2b, a mother board B; 3a, a daughter board A; 3b, a daughter board B; 4a1, 4a2, a connector; 5d, a cable D and 5b a cable B. 
     In the embodiment shown in FIGS. 1 and 2 the reference mother board 2a and the first other mother board 2b are provided with not only the daughter boards 3a, 3b but also the connectors 4a1, 4a2 for I/O signals. The reference mother board 2a is mounted on the case 1a and the connector al for I/O signals of the reference mother board 2a is mounted adjacent to the first other mother board 2b. Similarly, the first other mother board 2b is mounted adjacent to the reference mother board 2a on the case lb so that the distance between the connectors 4a1, 4a2 for I/O signals of both the reference mother board and the first other mother board is as short as possible to thereby minimize the length of the cable 5b. Further, a second other mother board 2b which is identical with the first other mother board 2b is mounted on the back of the first other mother board 2b by being rotated; i.e., its top and bottom being inverted with respect to those of the first other mother board 2b, thereby successfully minimizing the distance between the connector 4d for I/O signals of the second other mother board 2d and the connector 4a2 for I/O signals of the reference mother board 2a, which results in minimizing the length of the cable 5d. 
     In this case, as shown in FIG. 2, the cables 5b between the cable connectors 4a1 of the reference mother board 2a and the cable connectors 4b of the first other mother board 2b are connected so as to intersect, while the cables 5d between the cable connectors 4a2 of the reference mother board 2a and the cable connectors 4d of the second other mother board 2d are connected straight. Accordingly, it is possible to make the sums of the lengths of the cables 5a and 5b equal. In order to further shorten the lengths of the cables, 5d and 5b the reference mother board 5a in FIG. 1 may be shifted backward to such a position on the case 1a calculated as to minimize the cable lengths under discussion. 
     FIG. 3. is a plan view of another embodiment of this invention. In FIG. 3, reference numeral 2a&#39; designates a reference mother board; 3a&#39; a daughter board; 3b&#39;, 3d&#39; a daughter board; 5b&#39; a cable; and 5b&#39; a cable. 
     In this other embodiment of the invention shown in FIG. 3 both the reference mother board and the mother boards are mounted on one case. The two mother boards 2b&#39;, 2d&#39; are mounted below the reference mother board 2a&#39;. Also in this configuration, the daughter board 3a&#39; is mounted to the reference mother board 2a&#39; and the daughter boards 3b&#39;, 3d&#39; to the other mother boards 2b&#39;, 2d&#39;, both other mother boards 2b&#39;, 2d&#39;  being mounted with the top and bottom of the one board inverted with respect to those of the other. 
     Thus, also in this latter embodiment of the invention it is possible to minimize the lengths of the cables 5b&#39; and 5d&#39; interconnecting between the connectors 4a1&#39;, 4a2&#39;, 4b&#39;, 4d&#39; for I/O signals of both the reference mother board 2a&#39; and the two mother boards 2b&#39;, 2d&#39;. 
     As described above, according to this invention, it is possible to shorten the length of the cable between a reference mother board and a plurality of other mother boards, thereby improving the signal processing speed of an electronic device. According to this invention, it is also possible to mount the mother boards in parallel, thereby not only reducing the mounting space on the case substantially to a half that in the conventional art but reducing the maintenance space as well.