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Hercules Graphics Card

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The Hercules Graphics Card (HGC) is a computer graphics controller formerly made by Hercules Computer Technology, Inc. that combines IBM's text-only MDA display standard with a bitmapped graphics mode, also offering a parallel printer port.<ref name=":2" /><ref>Template:Cite web</ref> This allows the HGC to offer both high-quality text and graphics from a single card.

The HGC was very popular and became a widely supported de facto display standard on IBM PC compatibles. The HGC standard was used long after more technically capable systems had entered the market, especially on dual-monitor setups.

History

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The Hercules Graphics Card was released to fill a gap in the IBM video product lineup. When the IBM Personal Computer was launched in 1981, it had two graphics cards available: the Color Graphics Adapter (CGA) and the Monochrome Display And Printer Adapter (MDA). CGA offered low-resolution (Template:Resx) color graphics and medium-resolution (Template:Resx) monochrome graphics, while MDA offers a sharper text mode (equivalent to Template:Resx) but has no per-pixel addressing modes and is limited to a fixed character set.

These adapters were quickly found to be inadequate by the market, creating a demand for a card that offers high-resolution graphics and text.<ref>Template:Cite news</ref> The founder of Hercules Computer Technology, Van Suwannukul, created the Hercules Graphics Card so that he could work on his doctoral thesis on an IBM PC using the Thai alphabet, impossible with the low resolution of CGA or the fixed character set of MDA.<ref>Template:Cite news</ref> It initially retailed in 1982 for $499.<ref>Template:Cite news</ref>

Hardware design

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The original HGC is an 8-bit ISA card with 64 KB of RAM, visible on the board as eight 4164 RAM chips, and a DE-9 output compatible with the IBM monochrome monitor used with the MDA. Like the MDA, it includes a parallel interface for attaching a printer.<ref name=":2">Template:Cite news</ref>

The video output is 5 V TTL, as with the MDA card.<ref name="nemesis">Template:Cite web 070822 nemesis.lonestar.org</ref><ref name="ports">Template:Cite web</ref><ref>Template:Cite web</ref> Nominally, the Hercules card provides a horizontal scanning frequency of 18.425 ± 0.500 kHz and 50 Hz vertical.<ref name="industrial-monitors">Template:Cite web 070822 adm-electronic.de</ref> It runs at two slightly different sets of frequencies depending on whether in text or graphics mode, providing a different vertical refresh rate and a different aspect ratio via a different pixel clock and number of scanlines.Template:Citation needed

Capabilities

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File:Hercules Graphics Card test image.png
Wikipedia logo rendered at Template:Resx without aspect ratio correction
File:Wikipedia logo on Hercules display (adjusted).png
Wikipedia logo displayed on a CRT monitor by a Hercules-compatible video card
File:Hercules graphics simulated image.png
Hercules image at Template:Resx without aspect ratio correction
File:Hercules graphics (aspect ratio corrected).png
Hercules image with correct aspect ratio as would be seen on a 4:3 monitor

The Hercules card provides two modes:

The text mode of the Hercules card uses the same signal timing as the MDA text mode.

The Hercules graphics mode is similar to the CGA high-resolution (Template:Resx) two-color mode; the video buffer contains a packed-pixel bitmap (eight pixels per byte, one bit per pixel) with the same byte format—including the pixel-to-bit mapping and byte order—as the CGA two-color graphics mode, and the video buffer is also split into interleaved banks, each 8 KB in size.

However, because in the Hercules graphics mode there are more than 256 scanlines and the display buffer size is nearly 32 KB (instead of 16 KB as in all CGA graphics modes), four interleaved banks are used in the Hercules mode instead of two as in the CGA modes. Also, to represent 720 pixels per line instead of 640 as on the CGA, each scanline has 90 bytes of pixel data instead of 80.<ref name="manual101">Template:Cite book</ref>

The 64 KB RAM of the HGC can hold two graphics display pages. Either page can be selected for display by setting a single bit in the Mode Control Register. Another bit, in a configuration register exclusive to the HGC, determines whether the second 32 KB of RAM on the HGC is accessible to the CPU at the base address B8000h. This bit is reset at system reset (e.g. power-on) so that the card does not conflict with a CGA or other color card at address B8000h.<ref name="manual101b">Template:Cite book</ref>

Use

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In text mode, the HGC appears exactly like an MDA card.<ref name="wadlow198312">Template:Cite news</ref> Graphics mode requires new techniques to use. Unlike the MDA and CGA, the PC BIOS provides no intrinsic support for the HGC. Hercules developed extensions, called HBASIC, for IBM Advanced BASIC to add HGC support<ref>Template:Cite news</ref> and Hercules cards came with Graph X, a software library for Hercules graphical-mode support and geometric primitives.Template:R

Popular IBM PC programs such as Lotus 1-2-3 spreadsheet,Template:R AutoCAD computer-aided drafting, Pagemaker and Xerox Ventura desktop publishing, and Microsoft Flight Simulator 2.0 came with their own drivers to use the Hercules graphics mode.<ref>Template:Cite web</ref>

Though the graphics mode of the Hercules card is not CGA-compatible, it is similar enough to the two CGA graphics modes that with the use of third-party terminate-and-stay-resident programs it can also work with programs written for the CGA card's standard graphics modes. As the Hercules card does not actually have color-generating circuitry, nor can it connect to a color monitor, color appears as simulated grayscale in varying dithering patterns.<ref>Template:Cite web</ref><ref>Template:Cite web</ref><ref>Template:Cite web</ref>

Clones of the Hercules appeared, including generic models at very low prices, usually without the printer port. Hercules advertisements implied that use of generic Hercules clones can damage the monitor.<ref name="Byte_Magazine">Template:Cite news</ref>

Reception

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The Hercules Graphics Card was very successful, especially after Lotus 1-2-3 supported it, with one-half million units sold by 1985. Template:Asof Hercules Computer Technology had 18% of the graphics card market, second to IBM.<ref>Template:Cite news</ref> Hercules-compatible graphics cards shipped as standard hardware with most PC clones. As a de facto standard, support in software was widespread.<ref name=":0" />

Card versions

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The Hercules Graphics Card had several versions.

Hercules Graphics Card

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Several updated versions of the original Hercules Graphics Card exist. The original board from 1982 is referenced as GB100, with updated versions in 1983 (GB101), 1984 (GB102) and 1988 (GB102Z).<ref>Template:Cite web</ref>

Hercules Graphics Card Plus

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The Hercules Graphics Card Plus or HGC+ (GB112) was released in June 1986 at an original retail price of $299.<ref name="InfoWorld 1 Sep 19862">Template:Cite news</ref> It was an enhancement of the HGC, adding support for redefinable fonts called RAMFONT in MDA-compatible text mode.<ref name="Elliott_2012_HGCPlus2">Template:Cite web</ref> It was based around a specialty chip designed by Hercules Computer Technology, unlike the original Hercules Graphics Card, which used standard components.<ref>Template:Cite journal</ref> Software support included Lotus 1-2-3 v2, Symphony 1.1, Framework II and Microsoft Word 3.<ref name="InfoWorld 1 Sep 19862" />

Hercules Network Card Plus

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In 1988 Hercules released the Hercules Network Card Plus, (HNC NB112) a variant of the Graphics Card Plus with an integrated TOPS/FlashTalk-compatible network adapter.<ref>Template:Cite news</ref> Like the HGC+, it supported RAMFONT, but lacked a printer port.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite news</ref>

Hercules InColor Card

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Template:Main articles The InColor Card (GB222) was introduced in April 1987. It included color capabilities similar to the EGA, with 16 colors from a palette of 64. It retained the same two modes (Template:Resx text with redefinable fonts and Template:Resx graphics), and was backward-compatible with software written for the earlier monochrome Hercules cards.<ref name="Elliot_2012_InColor">Template:Cite web (Pictures and programming information)</ref><ref name="Wilton_1993">Template:Cite book (NB. The second edition does no longer discuss the InColor and MCGA cards at detail level.)</ref><ref name="Brown_2000_RBIL">Template:Cite web</ref><ref name=":02">Template:Cite web</ref><ref name=":1">Template:Cite news</ref>

Hercules Color Card

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The Hercules Color Card (GB200) was a CGA-compatible video board and should not be confused with the InColor Card.<ref>Template:Cite book</ref> This board could coexist with the HGC and still allow both graphics pages to be used.<ref>Template:Cite web</ref> It would detect when the second graphics page was selected and disable access to its own memory, which would otherwise have been at the same addresses. A version without printer port exists<ref>Template:Cite web</ref>

Hercules Text Card

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The Hercules Text Card was a text-only MDA clone, but offered a parallel printer port.<ref>Template:Cite web</ref>

Clone boards

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Other boards offered Hercules compatibility.<ref name="vgamuseum">Template:Cite web</ref>

Certain later models of the Tandy 1000 (such as the 1000 TL and SL) and the Epson Equity<ref name=":9">Template:Cite book</ref> contained circuitry built into their CPU boards that supported Hercules display modes in addition to their standard CGA modes.

See also

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References

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Further reading

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