See: "http://linuxtoday.com/high_performance/2003052701626NWHESV";
"The joke used to be that IBM's mainframes were the useless dinosaurs of computing. None of IBM's rivals are laughing now. With Linux gaining popularity on IBM's zSeries, the mainframe is making a strong comeback. "This really isn't news though. In 2001, 11% of IBM's new mainframes were being sold with Linux under the hood. Today, according to Joan Mestzeler, IBM's director of enterprise solutions for the zSeries, 17% of IBM's mainframe revenue is coming from Linux and that number is moving steadily upward. "IBM's not the only one doing well from Linux's big iron acceptance. Holger Dryoff, head of SuSE's American operations, says that SuSE's mainframe Linux; is accounting for almost 20% of SuSE's North American business. Other Linux companies--Red Hat and Turbolinux--support the IBM's zSeries, but SuSE is the leading mainframe Linux vendor..."
