Abstract:
An apparatus and method for a computer system to rapidly access at least two IDE disk drives. Use of standard forty pin connectors and forty wire ribbon cable having certain pairs of wires uniquely twisted so as to allow the system to independently access the IDE drives.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is related to the following U.S. patent application: Ser. No. 07/628,505. &#34;Method and Apparatus For Reducing Write Latency In Redundant Disk Arrays&#34; 
     Inventors: Parks, et al. Filed: Dec. 14, 1990 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The system and method of the present invention relates generally to computer digital storage systems, and in particular to computer systems using a plurality of disk drives. 
     2. Description of the Related Technology 
     Personal computers have gained substantial popularity among individual users for both business and home use. Personal computers are now being utilized for jobs heretofore performed by mainframe computers and minicomputers. The rapidly growing popularity in the use of personal computers may, in part, be attributed to the substantial improvement in both its speed of operation and its memory capacity of both random access memory (RAM) and disk. 
     Applications such as transaction-processing which have a high rate of random requests for small amounts of data, or large simulations requiring massive amounts of data that are in excess of the main memory capacity require memory storage capacity only available by using disk storage technology. Mass production of disk systems for personal computers have created low cost and high performance disks having data storage capacities of a hundred megabytes or more. Where a greater disk memory capacity is required, a number of these disks may be used. 
     Present disk drive technology has integrated the drive electronics (&#34;IDE&#34;) in with the drive itself, as in the Conner drive, type CP3204. However, the IDE drive was also intended to be software compatible with existing disk drive controllers such as the WD-1003 manufactured by Western Digital Corporation. Originally, the WD-1003 architecture disk drive controllers were designed to support two disk drives without IDE. IDE drives were adapted so that two could be used. This adaptation requires that both IDE drives monitor the task file register set in each controller, but only allows the drive selected by the drive bit in the SDH (select drive head) register to respond to read requests and to interpret commands. 
     This adaptation achieves compatibility with the WD-1003 type controller, however, it wastes IDE disk performance. Potential performance is lost because there are two disk drive controllers integral with the two IDE drives but only one controller may be used at a time. This limitation is mandated in order to maintain compatibility with existing disk controller system standards. 
     The prior art solved the limitation of only being able to access one drive at a time by utilizing a fifty pin connector on an Intelligent Disk Array (&#34;IDA&#34;) controller card and by connecting ten wires in the cable going from the IDA controller to each IDE drive. Connection of ten wires connected to pins 31 through 40 and connection of ten wires to pins 41 through 50 of the IDE connector made it unique for each drive. This method has the disadvantage of increasing the costs associated with the connector and cable, and, most importantly, it uses up precious space on the IDA controller card. 
     SUMMARY OF THE INVENTION 
     In contrast to prior methods and systems for rapid communication with two IDE drives, the system and method of the present invention uses a forty pin cable connector and forty wire cable in conjunction with a multi-disk adapter. The system and method of the present invention overcomes the problems and limitations of the prior art by utilizing unused wires in the cable, twisted in a unique way, so that standard IDE drive connections are maintained. By twisting four pairs of wires in the cable and utilizing unused connector pins at the controller, two interface control line sets are created on the same form factor as a standard IDE drive cable/connector set. 
     An IDE drive connector has forty pins arranged in two rows of twenty pins each. A forty conductor flat ribbon cable connects to each IDE connector and to the disk controller connector. Thirty-seven of the cable wires are used for signals and grounds, three wires are unused. The system and method of the present invention accomplishes the above results by utilizing the unused wires to carry additional control signals from the multi-disk adapter to the IDE disk drives without disturbing the standard signal wiring configuration to each IDE drive. The multi-disk adapter of the invention utilizes these unused wires to rapidly access both IDE drives in succession then allows both IDE disk drives to process the commands and data simultaneously. 
     The forty wire cable connects to a forty pin multi-disk adapter connector. Each wire connects to a corresponding pin on the adapter connector. The other end of the wires in this cable connect to another forty pin connector used for IDE disk drive 2. All wire connections to the connector pins of the adapter and the IDE disk drive 2 correspond except as follows; adapter connector pin 37 connects to IDE disk drive 2 pin 38, adapter connector pin 31 connects to IDE disk drive 2 pin 29, adapter connector pin 27 connects to disk 2 pin 25, and adapter connector pin 23 connects to IDE disk drive 2 pin 21. 
     The forty wire cable also connects to a third forty pin connector used for IDE disk drive 1. The same four pairs of wires are twisted again between the IDE disk drive 2 connector and the IDE disk drive 1 connector. Twisting of the four wire pairs a second time results in the original standard signal connections from the multi-disk adapter reappearing on the IDE disk drive 1 connector. By twisting the four wire pairs, the disk controller interface has two sets of input-output (&#34;I/O&#34;) read and write signals, two sets of interrupt request lines, and two chip select signals to control up to four IDE disk drives. 
     Placing the IDE disk drive 2 connector between the multi-disk adapter and the IDE disk drive 1 connector, and twisting the four wire pairs twice are for manufacturing convenience. As can be appreciated by those skilled in the art, the system and method of this invention are equally applicable to placing the IDE disk drive 1 connector between the multi-disk adapter connector and the IDE disk drive 2 connector, and twisting the four wire pairs only once, before the disk 2 connector. 
     An object of the present invention is to independently control at least two IDE disk drives over a forty wire cable. 
     A further object of the present invention is to utilize standard IDE disk drive connectors for connecting to at least two IDE disk drives. 
     Another object of the present invention is to uniquely twist four pairs of wires of a forty wire cable so that two sets of input-output read and write signals, two sets of interrupt request lines and two chip select signals are available for a multi-disk controller to independently control at least two IDE disk drives. 
     Still another object of the present invention is to rapidly control at least two IDE drives sequentially and have these drives continue to process commands and data simultaneously. 
     Yet a further object of the present invention to twist some of the cable wires so as to simplify the manufacture of the connector cable assembly. 
     Other and further objects, features and advantages will be apparent from the following description of a presently preferred embodiment of the invention, given for the purpose of disclosure and taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of the system of the present invention. 
     FIG. 2 is a schematic diagram of a connector/cable assembly of the present invention; 
     FIG. 3 is a partial schematic diagram of the connector/cable assembly of FIG. 2; 
     FIG. 4 is a schematic diagram of another embodiment of a connector/cable assembly of the present invention; and 
     FIG. 5 is a partial schematic diagram of the connector/cable assembly of FIG. 4. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, the details of the preferred embodiment are schematically illustrated. In the drawings the letter S designates generally the connector/cable system of the invention. 
     FIG. 1 illustrates processor 10 (an Intel type 80386 in this preferred embodiment) connected to multiple disk adapter 11 through data bus 14, address bus 15, and control bus 16. Multiple disk adapter 11 simply enables communication between processor 10 and the integrated controllers in drives 1 (13) and 2 (12). Adapter 11 is a programmable array of logic (PAL) in this preferred embodiment but may take any other desired form to perform its simple function. 
     Multiple disk adapter 11 is connected through cable 150 to connector 100. Connector 100 connects through cable 150 to connector 102. The cabling to and from connector 102 contains twisted pairs of wires which will be described below. Connector 102 is connected to drive 2 and to connector 104 through cable 150. Connector 104 connects to drive 1 through cable 150. 
     In FIG. 2, the connector/cable system S connects to multi-disk adapter 11 by connector 100, a first IDE disk drive 13 by connector 104 and a second IDE disk drive 12 by connector 102. Forty wires 150 i , where i=1 to 40, connect to connector pins 1-40 of connectors 100, 102 and 104. These forty wires may be comprised of a flat ribbon cable or any other type of cable easily adaptable for connection to the pins of edge connectors. 
     Pins 1-20 of connectors 100, 102 and 104 are connected in parallel by means of cable wires 150 i . All pins of connector 100 are connected to correspondingly numbered connector pins of connector 104 by means of wires 150 i . All pins of connector 100 are connected to correspondingly numbered connector pins of connector 102 except for pins 21, 23, 25, 27, 29, 31, 37 and 38. Connector 102 has eight pin connections transposed by twisting four pair of wires 150 i . 
     Referring now to FIG. 3, four pair of twisted wires are illustrated. Wires 110 and 112 from the first pair, wires 114 and 116 form the second pair, wires 118 and 120 form the third pair and wires 122 and 124 form the fourth pair. The first twist in the first pair of wires 110 and 112 connect pins 21 and 23 of connector 100 to pins 23 and 21 respectively of connector 102. The first twist in the second pair of wires 114 and 116 connect pins 25 and 27 of connector 100 to pins 27 and 25 respectively of connector 102. The first twist in the third pair of wires 118 and 120 connect pins 29 and 31 of connector 100 to pins 31 and 29 respectively of connector 102. The first twist in the fourth pair of wires 122 and 124 connect pins 37 and 38 of connector 100 to pins 39 and 38 respectively of connector 102. 
     In similar fashion, the second twist in the first pair of wires 110 and 112 connect pins 23 and 21 of connector 102 to pins 21 and 23 respectively of connector 104. The second twist in the second pair of wires 114 and 116 connect pins 27 and 25 of connector 102 to pins 25 and 27 respectively of connector 104. The second twist in the third pair of wires 118 and 120 connect pins 31 and 29 of connector 102 to pins 29 and 31 respectively of connector 104. The second twist in the fourth pair of wires 122 and 124 connect pins 38 and 37 of connector 102 to pins 38 and 39 respectively of connector 104. 
     These twists are inserted into the cable for ease in manufacturing, once before drive 2 connector 102 and once again after drive 2 connector 102 but before drive 1 connector 104. The twists allow different control signals from the multi-disk adapter connector 100 to control each IDE drive independently of the other IDE drive. The multi-disk adapter has two I/O read (DIOR1 and DIOR2) control lines, two I/O write (DIOW1 and DIOW2) control lines, and two interrupt request (INTRQ1 and INTRQ2) lines. Chip selects (CS1-3 and CS3-1) are transposed between the two IDE drives connected to the cable. 
     The multi-disk adapter accesses IDE drive 1, which is the second drive on the cable at connector 104 having the untwisted signals, by either requesting a read (DIOR1) or write (DIOW1) operation and applies chip select 1 to CS1-3 and chip select 3 to CS3-1. The IDE drive 1 responds with interrupts on INTRQ1. The multi-disk adapter accesses IDE drive 2, which is the first drive on the cable at connector 102 having the twisted signals, by either requesting a read (DIOR2) or write (DIOW2) operation and applies chip select 1 to CS3-1 and chip select 3 to CS1-3. The IDE drive 2 responds with interrupts on INTRQ2. 
     Only one IDE drive may be accessed at a time, however, accessing by the multi-disk adapter is extremely brief, the majority of the actual disk operations are handled by the internal IDE disk controllers. In addition, up to two more IDE drives may be connected in a similar fashion and accessed by proper coding of the chip selects. 
     Referring now to FIG. 4, another embodiment of the invention is illustrated. All pins of connector 100 are connected to correspondingly numbered connector pins of connector 104 by means of wires 150 i . All pins of connector 104 are connected to correspondingly numbered connector pins of connector 102 except for pins 21, 23, 25, 27, 29, 31, 37 and 38. Connector 102 has eight pin connections transposed by twisting four pair of wires 150 i . 
     Referring now to FIG. 5, between connectors 102 and 104 four pair of twisted wires are illustrated. Wires 110 and 112 form the first pair, wires 114 and 116 form the second pair, wires 118 and 120 form the third pair and wires 122 and 124 form the fourth pair. Twisting the first pair of wires 110 and 112 connect pins 21 and 23 of connector 104 to pins 23 and 21 respectively of connector 102. Twisting the second pair of wires 114 and 116 connect pins 25 and 27 of connector 104 to pins 27 and 25 respectively of connector 102. Twisting the third pair of wires 118 and 120 connect pins 29 and 31 of connector 104 to pins 31 and 29 respectively of connector 102. Twisting the fourth pair of wires 122 and 124 connect pins 37 and 38 of connector 104 to pins 39 and 38 respectively of connector 102. These twists are inserted into the cable between drive 1 connector 104 and drive 2 connector 102, allowing different control signals from the multi-disk adapter connector 100 to control each IDE drive independently. 
     The system and method of the present invention, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned as well as others inherent therein. While a presently preferred embodiment of the invention has been given for the purpose of disclosure, numerous changes in the details of construction and arrangement of parts will readily suggest themselves to those skilled in the art and which are encompassed within the spirit of the invention and the scope of the appended claims.