SUPERMAC AND RASTEROPS BATTLE OVER GRAPHICS PATENTS The rivalry between computer graphics concerns SuperMac Technology and RasterOps Corporation is heating up. Yesterday, SuperMac denounced RasterOps for sending SuperMac a letter earlier this week, in which RasterOps accused SuperMac of patent violations. SuperMac labeled the letter an "unfounded and blatant threat". In the letter, wich RasterOps confirmed, RasterOps warned that SuperMac dealers, distributors and customers would be "duly concerned" if SuperMac persists in the alleged patent violations. The two companies have been slugging it out all year for market share in the fiercely competitive computer graphics business. SuperMac has had the better year so far in 1993, posting record earchings, while RasterOps recently estimated it had a significant operating loss in its first quarter ending September 30. [Wall Street Journal 10/13/93, B9]