公开(公告)号：JPH07210141A

公开(公告)日：1995-08-11

申请号：JP26657094

申请日：1994-10-31

Applicant: IBM

Inventor： SUTEFUAN PATORITSUKU TONPUSON ,  DAAUIN PII RATSUKUREI ,  SHIYAAUTSUDO BURANNON

IPC: G09G5/393 ,  G09G5/00 ,  G09G5/36 ,  G09G5/39 ,  G09G5/395

Abstract: PURPOSE: To provide a method and device for supporting the virtualization of a VGA graphics mode during the native mode operation of an XGA display adapter. CONSTITUTION: In order to make the virtualization of a VGA graphics mode possible during the native mode operation of an XGA display adapter, the adapter is selectively enabled by making VGA graphics supporting hardware 208 and a specific VGA register accessible. The XGA display adapter contains an XGA operation mode register having three control bits and the register is selectively written by means of application software so as to permit or inhibit a virtual VGA function. When the virtual VGA function is permitted, a logic circuit in a host interface 200 discriminates whether each video memory access is not native memory access, but contains virtual VGA memory access, by checking CPU addresses related to each video memory access.