VGA_ATC_DATAR
regval = bus_space_read_1(iot, ioh_vga, VGA_ATC_DATAR);
if (bus_space_read_1(iot, ioh_vga, VGA_ATC_DATAR) != (regval ^ 0x0f))
res = vga_raw_read(vh, VGA_ATC_DATAR);