Hercules Graphics Card

The Hercules Graphics Card was basically MDA with addressable pixels.

IBM had created the Monochrome Display Adapter standard (MDA) to satisfy the business market that desired text display and according to conventional wisdom didn't need the added expense of color or color graphics. The theoretical maximum resolution was 80x25 text characters with 4 intensities (720x350x4). However, the MDA internal buffer was limited to 256 scanlines, requiring interlacing to create a video frame. The card could not address pixels so no graphics were possible. The hardware actually allowed for 8 colors, but this was not documented and never used. CGA cards could simulate MDA mode (and in color). But the result was eye-straining artifacted blurry text even on the best monitor to match the mode. Most monitors were not 720x350, so the result was awful most of the time. True MDA hardware was the superior text display option. People desiring the best graphics for each purpose would use a CGA card and an MDA card together in the same computer and have two monitors connected. As CGA and MDA did not occupy the same memory in the system BUS, both monitors could be used simultaneously (IBM intended this). Hercules card supported two graphic pages in memory. If only the upper memory page was used then a concurrent CGA card could use another monitor.

Hercules hardware could automatically emulate CGA by reducing it to greyscale. Some say this was a better way to see most CGA games. It could also display text by reducing Hercules mode to CGA resolution but this resulted in "squashed" text. But on a CGA optimized monitor, Hercules could do sharper clearer text than

Although in monochrome, the 720x350 mode was the maximum possible resolution on IBM-PC and compatibles for a relatively long period. Using 4 interleaved VRAM banks meant the was no need for interlacing, so superior animation. Even after EGA was introduced, Hercules mode was the superior option for graphics that only required greyscale color.

The Tandy 1000 and Epson Equity used cloned Hercules hardware on the motherboard to provide Hercules mode support. Nearly all VGA and later cards will display Hercules graphics.