0xB0C2 - 15, 16, 24 and 32 BPP modes, support for linear frame buffer, support for retaining memory contents on mode switching.0xB0C1 - virtual width and height, X and Y offset.0xB0C0 - setting X and Y resolution and bit depth (8 BPP only), banked mode.Six versions of the BGA have existed, of which 0xB0C5 is the current version (as of 2009, Bochs version 2.4). They are used in the sections below, with their numerical value between parentheses.Īs Bochs has evolved, so has the BGA. The names of these defines all start with VBE_DISPI. The Bochs sources define in vga.h, located in the subdirectory iodev/, a number of defines that are useful for programming the BGA. QEMU (with the -std-vga command line argument) also uses the latest version. There are six versions of the BGA (0xB0C0 through 0xB0C5), but if you use the latest version of Bochs you only need to concern yourself with the latest one (0xB0C5). Via these ports it is possible to enable or disable the VBE extensions, change the screen resolution and bit depth, and manage a larger virtual screen. The first one is an index port, the second one a data port (comparable to how the VGA handles its sets of registers). The Bochs emulated graphics hardware (henceforth called BGA for Bochs Graphics Adaptor) is accessed via two 16-bit IO-ports.

3.4 Setting display resolution and bit depth.

Bochs cmos