Abstract: A personal computer has a memory system including a write-through cache which is accessible by more than one device. A snoop mechanism includes logic that monitors bus master control signals to determine if a new memory write cycle has been started before a current snoop cycle has finished. If a new cycle has been started, then a corresponding snoop cycle occurs which overlaps the new memory cycle and is pipelined with the previous snoop cycle so that the snooping mechanism does not fall behind the memory write cycles.

Abstract: An address decoder is connected to an address bus and comprises a plurality of latches for latching address signals from the address bus. Decode logic is connected to use unlatched addresses from the address bus or latched addresses from the latches. The decoder is selectively operable to decode addresses in two modes, an unlatched mode and a latched mode dependent upon system frequency. The decode logic produces a signal that is transmitted into a state machine for controlling operation thereof.

Abstract: An all points addressable raster scan graphics display system is operable in two modes. In the first mode, data is extracted from a refresh store, serialized, modified, and applied to a display device at a first frequency. In the second mode, data is extracted from the refresh store, serialized and partially modified at said first frequency, but it is then further modified and passed to the display device at an even sub harmonic, for example half, of the first frequency. The further modification includes concatenation of successive groups of display data bits. Accordingly, with the raster scan device operating at a constant scan velocity, the first mode provides a high picture element definition but relatively low color definition display, and the second mode provides a display with an even submultiple, for example half, the picture element definition but considerably greater color definition.

Abstract: A device for automatically controlling the movement of a welding torch (10) while welding an elongated joint (18). A charge injection television camera (30) is carried on a movable support (20) and includes a matrix of individual light sensing video elements (pixels, 32) which generate voltages responsive to light reflected off of the joint (18) and surrounding areas of the workpiece (12). The voltages produced by the pixels (32) are converted to digital words which are fed to a microprocessor (54) for generating an error signal. This error signal is fed to a digital motor (26) which is used to drive a movable support (20) upon which the television camera (30) is carried.