VGA_CRTC_V_BLANK_END
vga_wcrt(regbase, VGA_CRTC_V_BLANK_END, vtotal & 0xff);
par->crtc[VGA_CRTC_V_BLANK_END] = (yres + lower - 1 + vslen) & 0xFF;
write3X4(par, VGA_CRTC_V_BLANK_END, vblankend & 0xFF);
par->crtc[VGA_CRTC_V_BLANK_END] = pos & 0xFF; /* 0x7F for original VGA,