Hercules Graphics Card

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Hercules Graphics Card
HGC with parallel port
Release date1982; 42 years ago (1982)
ArchitectureMotorola 6845
Cards
Entry-levelHercules Graphics Card
Mid-rangeHercules Graphics Card Plus
High-endHercules InColor Card
History
PredecessorMDA, CGA
SuccessorEnhanced Graphics Adapter

The Hercules Graphics Card (HGC) is a computer graphics controller made by Hercules Computer Technology, Inc. that combines IBM's text-only MDA display standard with a bitmapped graphics mode. 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

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 offers low-resolution (320x200) color graphics and medium-resolution (640x200) monochrome graphics, while MDA offers a sharper text mode (equivalent of 720×350) but has no per-pixel addressing modes and has 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.[1] 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.[2] It initially retailed in 1982 for $499.[3]

Hardware design

The original HGC is an 8-bit ISA card with 64KB 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.[4]

The video output is 5V TTL, as with the MDA card.[5][6] Nominally, the Hercules card provides a horizontal scanning frequency of 18.425 ±0.500 kHz, and 50 Hz vertical.[7] It runs at two slightly different frequencies depending on whether in text or graphics mode, due to the slight difference in horizontal resolution.[citation needed]

Capabilities

Wikipedia logo displayed on a CRT monitor by a Hercules-compatible video card
Simulated Hercules image at 720x348 (no aspect ratio correction)
Simulated Hercules image with the correct aspect ratio (as would be seen on a 4:3 monitor)

The Hercules card provides two modes: an MDA-compatible monochrome text mode, and a pixel-addressable graphics mode at 720x348.[8]

Modes:

  • 80×25 text mode with 9×14 pixel font (effective resolution of 720×350)
  • 720×348 graphics mode

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 (640×200) 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.[citation needed]

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.[citation needed]

Use

In text mode, the HGC appears exactly like an MDA card.[9] 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[10] and Hercules cards came with Graph X, a software library for Hercules graphical-mode support and geometric primitives.[9]

Popular IBM PC programs such as Lotus 1-2-3 spreadsheet,[9] 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.[11]

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 TSRs 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 greyscale in varying dithering patterns.[12]

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.[13]

Reception

The Hercules Graphics Card was very successful, especially after Lotus 1-2-3 supported it, with one half million units sold by 1985. As of June 1986 Hercules Computer Technology had 18% of the graphics card market, second to IBM.[14] Hercules-compatible graphics cards shipped as standard hardware with most PC clones. As a de facto standard, support in software was widespread.[8]

Later cards

The Hercules Graphics Card was followed by several other Hercules cards.

Hercules Graphics Card Plus (HGC+)
This card was released in June 1986 by Hercules Computer Technology, Inc. at an original retail price of $299.[15] It was an enhancement of the HGC, adding support for redefinable fonts called RAMFONT in MDA compatible text mode.[16][17] It was based around a specialty chip designed by Hercules Computer Technology, unlike the original Hercules Graphics Card which used standard components.[18] Software support included Lotus 1-2-3 v2, Symphony 1.1, Framework II and Microsoft Word 3.[15]
Hercules Network Card Plus
In 1988 Hercules released the Network Card Plus, a variant of the Graphics Card Plus with an integrated TOPS/FlashTalk-compatible network adapter.[19] Like the HGC+ it supported RAMFONT, but lacked a printer port.[20][21][22]
Hercules InColor Card
April 1987. Included color capabilities similar to the EGA, with 16 colors from a palette of 64. It retained the same two modes (80×25 text with redefinable fonts and 720×348 graphics), and was backward compatible with software written for the earlier monochrome Hercules cards.
Hercules Color Card
Not to be confused with the InColor Card. A CGA-compatible video board. This board could coexist with the HGC and still allow both graphics pages to be used. 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.

Clone boards

Tseng ET-1000 board
ATI Hercules-compatible card from 1986
A Tamarack Microelectronics HGC-compatible card

Other boards offered Hercules compatibility.[23]

Certain later models of the Tandy 1000 (such as the 1000 TL and SL) and the Epson Equity contained circuitry built into their CPU boards that supported Hercules display modes in addition to their standard CGA modes.

See also

References

  1. ^ Inc, InfoWorld Media Group (1988-09-19). InfoWorld. InfoWorld Media Group, Inc. {{cite book}}: |last= has generic name (help)
  2. ^ Inc, Ziff Davis (1989-05-16). PC Mag. Ziff Davis, Inc. {{cite book}}: |last= has generic name (help)
  3. ^ Inc, InfoWorld Media Group (1986-09-01). InfoWorld. InfoWorld Media Group, Inc. {{cite book}}: |last= has generic name (help)
  4. ^ Inc, InfoWorld Media Group (1982-09-27). InfoWorld. InfoWorld Media Group, Inc. {{cite book}}: |last= has generic name (help)
  5. ^ "IBM PC-Compatible EGA Video Reference". Archived from the original on 2014-05-11. Retrieved 2007-08-22. 070822 nemesis.lonestar.org
  6. ^ "Monitor Ports". 071105 whitefiles.org
  7. ^ "Industrial monochrome monitors 7" - 14"" (PDF). Archived from the original (PDF) on 2007-02-02. 070822 adm-electronic.de
  8. ^ a b Inc, InfoWorld Media Group (1989-06-26). InfoWorld. InfoWorld Media Group, Inc. {{cite book}}: |last= has generic name (help)
  9. ^ a b c Wadlow, Tom (December 1983). "The Hercules Graphics Card". BYTE. p. 343. Retrieved 2013-10-20.
  10. ^ The Hercules Graphics Card, December 1983, BYTE Magazine (PDF). 1983.
  11. ^ "Microsoft Flight Simulator (v2.0) Covers (PC Booter)".
  12. ^ "ibm pc - How do CGA emulators for Hercules graphics work?". Retrocomputing Stack Exchange. Retrieved 2021-02-07.
  13. ^ "Hercules ad from Byte Magazine April 1985". Byte Magazine. April 1985.
  14. ^ Enterprise, I. D. G. (1986-06-23). Computerworld. IDG Enterprise.
  15. ^ a b InfoWorld 1 Sep 1986, p. 41, at Google Books
  16. ^ Elliott, John C. (2012-08-09). "Hercules Graphics Card Plus: Notes". Archived from the original on 2016-11-23. Retrieved 2016-11-23.
  17. ^ Inc, InfoWorld Media Group (1986-09-01). InfoWorld. InfoWorld Media Group, Inc. {{cite book}}: |last= has generic name (help)
  18. ^ "Inside the IBM PC: Before you consider the Hercules Graphics Card Plus consider the technology behind it". Byte Magazine (Advertisement). 11. October 1986. Retrieved 2016-11-24.
  19. ^ Inc, InfoWorld Media Group (1988-03-21). InfoWorld. InfoWorld Media Group, Inc. {{cite book}}: |last= has generic name (help)
  20. ^ CW (1988-04-22). "Hercules bringt neues PC-Board mit Ramfont: Grafik und Netzwerk auf einer Karte". Computerwoche (in German). Retrieved 2016-11-24.
  21. ^ "Hercules Network Card Plus". PC Magazine. 1988-05-31. Retrieved 2016-11-24.
  22. ^ Inc, InfoWorld Media Group (1987-10-26). InfoWorld. InfoWorld Media Group, Inc. {{cite book}}: |last= has generic name (help)
  23. ^ "VGA Legacy". Archived from the original on 2014-06-29. Retrieved 2014-06-28.

Further reading

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