CRTC
uint16_t saved_r21 = CRTC.r21;
CRTC.r21 = (mode & 0x0f) | 0x0100;
CRTC.r22 = (src << 8) | dst; /* specify raster number */
CRTC.crtctrl = 0x0008;
CRTC.crtctrl = 0x0000;
CRTC.r21 = saved_r21;
CRTC.r21 = 0x0100 | ip->fgcolor << 4;
CRTC.r21 ^= 0x00f0;
CRTC.r21 = 0;
CRTC.r10 = 0;
CRTC.r11 = tv_top * FONTHEIGHT;
CRTC.r21 = 0x01f0;
CRTC.r21 = 0;
CRTC.r11 = tv_top * FONTHEIGHT;
CRTC.r11 = tv_top * FONTHEIGHT;