Abstract: A graphics controller that uses two MREQ priority levels (low and high) to retrieve display data from a frame buffer into a CRT FIFO. The graphics controller sends the high priority MREQ signal to a host controller if the data level in the CRT FIFO is below a low level water mark. The graphics controller sends the low priority MREQ signal if the data level in the CRT FIFO is between a high level water mark and a low level water mark, and if a system memory bus is idle. The host controller grants access of the system memory bus to the graphics controller with a higher priority (i.e. above that of other devices such as CPU and I/O devices) in response to the high priority MREQ signal, and with a lower priority in response to the low priority MREQ signal. Upon being granted access to the system memory bus, the graphics controller retrieves display data from the frame buffer.

Abstract: A device for use in a computer system, particularly a personal computer (PC) which provides compatibility for a proposed ISA plug and play (PNP) standard. The device of the present invention is also backward compatible with non-PNP (legacy) PCs. Upon power-up, a device may initialize using default traditional or specification (ISA) values for I/O address, IRQ and DMA channels. If PNP activity by the host PC is detected by the device, the device is disabled, and awaits activation and I/O address, IRQ and DMA channel assignments from a host PC. If no PNP activity by a host PC is detected, the device continues to operate using default traditional or specification (ISA) I/O address, IRQ and DMA channels. The device of the present invention may be installed in PNP or legacy type PCs without reconfiguring hardware (e.g., DIP switches, jumpers or the like) in the device or installing new firmware, operating system, or applications software in a host PC.

Abstract: A computer system including one or more PCMCIA expansion slots allows video and/or audio capabilities to be added to the system through a standard PCMCIA interface, utilizing multimedia type PCMCIA peripheral cards. A PCMCIA host adapter integrated circuit interrogates a PCMCIA peripheral card to determine whether or not the PCMCIA peripheral card is a multimedia type PCMCIA peripheral including video or audio capability. If the PCMCIA peripheral card is a multimedia type peripheral, the PCMCIA host adapter integrated circuit couples the PCMCIA peripheral card directly to the graphics and sound controller integrated circuits, using the standard PCMCIA interface and bypassing the host system bus. Otherwise, if the PCMCIA peripheral card is a standard PCMCIA peripheral, then the PCMCIA host adapter integrated circuit interfaces communications between the PCMCIA peripheral card and the host system bus in a conventional manner.