A system is disclosed for a computer to communicate with a selected one of a plurality of other computers through two identical communications links associated with the communicating computers. A single channel connects the two links which operate at a clock rate independent of the computers. Binary digits and clock pulses are combined and converted into a three-level signal for serial transmission over the single channel. Both control messages and data words may be transmitted. Each message and...

The invention is used in a computer system to buffer the transfer of program portions from a system having a first bus width to instruction processing logic having a second bus width. An instruction register receives program portions via a system bus from the program memory. A state register stores a code specifying the action to be taken to transfer the next program portion from the instruction register to the instruction processing logic. Control logic, upon receiving a request for the next pr...

Multiple computer system in which a control signal manifestation is circulated by a single control line from one computer to the next to indicate that the computer receiving the control signal manifestation may have available to it for communication with another computer a common communications channel. If, upon receipt of a control signal manifestation, a computer desires to transmit via the channel, it "captures" the control signal manifestation. If not, or after a computer has completed its c...

Improved parallel-processor computer systems and improved data transfer systems incorporating novel networks for inter-machine communication. In a first type of communication system, tree wiring is employed in which the maximum number of outgoing inter-machine communication channels required for any machine of a set of data handling machines to communicate with any other machine of the set is equal to the maximum number of such channels required for communication between a root machine of the se...

A mouse for a computer having a longitudinal slot formed in a side wall of the mouse body through which the mouse cable passes to the computer. The guide slot is notched along one edge with rounded grooves for removably receiving a connector of the mouse cable and thereby selectively adjusting the connected position of the cable at the side wall of the mouse in accordance with the size and configuration of the hand of a user. A pointer in the form of an arrow extends forwardly at the front of th...

A memory expansion circuit for expanding computer memory capacity requiring a minimum of alterations to the host system is disclosed. The memory expansion circuit is parasitic in that it fully exploits address lines, data input and output lines, and control lines already available in the existing host computer system, and it is suitable for use with both static and dynamic memory devices. In a preferred embodiment, a bank of memory devices which responds to a single memory read or write operatio...

A drawing device having a platform from which a marking instrument is suspended and wheels for moving the instrument over the surface of a drawing medium, a pair of these wheels being mounted equidistantly on opposite sides of the instrument, each of the pair of wheels being mounted to rotate freely, another of these wheels being a drive wheel depending from the platform and separated from the instrument on a line therefrom perpendicular to a line connecting the pair of wheels and the instrument...

An apparatus for operational analysis of computing devices which, when coupled to the address, data, and control buses of a computer, displays a representation of a selectable subgroup of the bus signals on a bit map display for each occurrence of a selectable condition. The bits of the least and most significant halves of the selected subgroup define the horizontal and vertical coordinates of a display pixel activated upon occurrence of the selectable condition. Selectable groups are address an...

The method for diagnosing microprogrammed computers consists of locating malfunctioning computer circuits with the aid of basic control data from which individual basic control words are selected under the control of diagnostic control data, and activating those basic microorders contained in the selected basic control words which provide for execution of a predetermined diagnostic procedure. A device for effecting the above method comprises two groups of NAND gates, as well as two flip-flops. T...

A microprogram store having an updating store for holding substitute information elements for use with a fixed microprogram store of an electronic computer, such substitute information elements being replacements for corresponding erroneous or missing information elements in the fixed store, wherein the updating store is an erasable store operated in parallel with the fixed store and supplying an information element held therein whenever an information element in the fixed store is addressed and...