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ADDRESSING METHOD to SUPPORT VIDEO MEMORY INTERLEAVING

IP.com Disclosure Number: IPCOM000057232D
Original Publication Date: 1988-Apr-01
Included in the Prior Art Database: 2005-Feb-15

Publishing Venue

IBM

Related People

Authors:
McNeil, WL [+details]

Abstract

A technique is described whereby an address mapping method maximizes video memory bandwidth by supporting interleaving without sacrificing the performance of the microprocessor interface. The concept is used in video graphics array (VGA) circuitry, as used in the IBM Personal System/2, Models 50, 60 and 80, and is particularly useful in expediting video memory access. (Image Omitted) The VGA circuitry interfaces between video memory and the central processing unit (CPU), as shown in Fig. 1. Fig. 1 illustrates the all- points-addressable (APA) configuration of the VGA circuitry. The VGA chip arbitrates requests for video memory utilization from both the CPU and the cathode ray tube controller (CRTC) circuitry contained within the VGA chip.