
The Vision964 driver had some difficulties in setting up the following mode:

mode = {
  {{ 800, 400},  /* visible */
   { 800, 400},   /* virtual */
    { 240, 180},   /* size [mm] */
    text,
    { 8, 16}},   /* textgrid */
    { 800, 808, 816, 936, 984, 1000, 0}, /* x timing */
    { 400, 407, 412, 414, 439, <6>Nov 18 20:42:30 kernel:    { 1, 1},   /* magnify */
    100,          /* flags   */
    31420450,          /* dclk    */
    { 1, 1},   /* clk     */
    { 1, 1}    /* lclk    */
}

Effect was that half the screen was blanked. I tracked this down to a bug in
setup of x.blankend but I don't understand why. Decreasing x.blankend by one
solved the problem but there is no significant change in the register setting.
(setting an overflow bit or something like that...)

