topcat —
HP98544 98550 “Topcat” and “Catseye”
  device interface
topcat* at intio?
topcat* at dio? scode ?
wsdisplay* at topcat?
This driver is for the HP98544, 98545 and 98547 “Topcat” and
  HP98548, 98549, and 98550 “Catseye” display cards. This driver
  merely checks for the existence of the device and does minimal setup, as it is
  expected the applications will initialize the device to their requirements.
  The Topcat and Catseye are nearly identical in common usage and only the
  Topcat will be referred to from now on.
The Topcat display cards are not user configurable. If one is
    present on a system, it will always have a frame buffer address of 0x200000
    and a control register address of 0x560000. These are the HP series 300 ITE
    (Internal Terminal Emulator) defaults. The device can also be used as a
    graphics output device.