double-scan CGA

Bright Text on 1-bit Displays

  • by

XT-class Toshiba laptops started to use “double-scan CGA” displays with a resolution of 640×400 in the late 80s. This allowed for better graphics and much sharper text in comparison with ordinary CGA solutions. However, the LCDs which Toshiba used worked only in 1-bit mode so there were no shades of grey (blue). Lower resolutions in graphics emulated (four) colors using 2×2 patterns. The text mode, on the other side, emulated the intensity bit (bright text) using bolt characters.

Toshiba experimented a lot with hi-res fonts in ROM and I’m not pleased with the results. Standard (thin) font is hard to read and not visually appealing. Fortunately, it is possible at least to swap the bold and standard fonts using a keyboard shortcut. It is strange that the highlighted characters are in fact less readable then but overall experience is still better than with the default setup.