Apparatus and method for terminating a computer memory bus

An electronic device which comprises:

• a multiplicity of printed circuit boards, each board further comprising a multiplicity of electronic components having a capacitance, and a comb of connecting terminals;
• a motherboard;
• a bus, having a characteristic impedance, contained on the motherboard;
• a multiplicity of connectors electrically connected to the bus, into each of which except one the comb of a corresponding board is matingly inserted and electrically connected, the terminals presenting a capacitance to the bus including the capacitance of the components;
• a switch mounted onto each such board in proximity to the comb, having an on state and an off state, and having an input and output, in which the input is connected to the output via a low resistance in the on state and a high resistance in the off state;
• a plurality of leads conductively connecting the combs and the input of the switch for each such board;
• a plurality of leads conductively connecting the output of the switch and the electronic components;
• selection means to simultaneously turn the switch of a single selected board on, while maintaining the non-selected boards off;
• and
• a terminator board further comprising:
• a) a comb of connecting terminals,
• b) one or more switches, each having an on state and an off state, and each having an input and output, in which the input is connected to the output via a low resistance in the on state and a high resistance in the off state, and mounted to the board in proximity to the comb;
• c) one or more termination chips, each of which is electrically connected to the output of a corresponding switch by a plurality of leads, and each of which presents an impedance to the output of the corresponding FET switch;
• d) a plurality of leads conductively connecting the comb and the switches;
• e) selection means to turn the switches for terminator board on or off, so that only a single board is connected to the bus at any time, and the terminator board presents the characteristic impedance of the bus.

An electronic apparatus comprising:

• one or more printed circuit boards;
• a multiplicity of electronic components mounted on each board, each electronic component having a capacitance;
• a bus, having a characteristic impedance;
• a switch located on each board, the switch having an on state and an off state, each switch having a low resistance in the on state and a high resistance in the off state;
• a plurality of leads conductively connected to between the bus and the switches;
• a plurality of leads conductively connected between the switches and the electronic components;
• selection means to simultaneously turn the switch of a single selected board on, while maintaining the non-selected boards off, and
• a terminator board further comprising:
• a) a comb of connecting terminals,
• b) one or more switches, each having an on state and an off state, and each having an input and output, in which the input is connected to the output via a low resistance in the on state and a high resistance in the off state, and mounted to the board in proximity to the comb;
• c) one or more termination chips, each of which is electrically connected to the output of a corresponding switch by a plurality of leads, and each of which presents an impedance to the output of the corresponding FET switch;
• d) a plurality of leads conductively connecting the comb and the switches;
• e) selection means to turn the switches for terminator board on or off, so that only a single board is connected to the bus at any time, and the terminator board presents the characteristic impedance of the bus.

An electronic apparatus comprising:

• a motherboard of insulating substrate having a network of conductive leads applied thereto, pads located on the motherboard for attaching memory elements,
• a multiplicity of memory elements mounted on the motherboard via the pads;
• a bus, having a characteristic impedance, conducting data and address leads to the memory elements;
• a plurality of switching devices having an on state and an off state, each switching device having a low resistance in the on state and a high resistance in the off state;
• a plurality of leads conductively connected to between the bus and the switching devices;
• a plurality of leads conductively connected between the switching devices and the memory element;
• means to turn selected switches on and off;
• and
• a terminator board further comprising:
• a) a comb of connecting terminals,
• b) one or more switches, each having an on state and an off state, and each having an input and output, in which the input is connected to the output via a low resistance in the on state and a high resistance in the off state, and mounted to the board in proximity to the comb;
• c) one or more termination chips, each of which is electrically connected to the output of a corresponding switch by a plurality of leads, and each of which presents an impedance to the output of the corresponding FET switch;
• d) a plurality of leads conductively connecting the comb and the switches;
• and
• e) selection means to turn the switches for terminator board on or off;
• so that connections to the bus are made to selected memory elements only, the non-selected memory elements being isolated from the bus, and the terminator board presents the characteristic impedance of the bus.