Editing Hercules Graphics Card (section)

== Hardware design ==
The original HGC is an [[Industry Standard Architecture|8-bit ISA]] card with 64&nbsp;KB of [[Random-access memory|RAM]], visible on the board as eight 4164 RAM chips, and a [[D-subminiature|DE-9 output]] compatible with the [[IBM 5151|IBM monochrome monitor]] used with the MDA. Like the MDA, it includes a parallel interface for attaching a printer.<ref name=":2">{{Cite news |date=27 September 1982 |title=Hardware News |pages=77 |work=InfoWorld |url=https://books.google.com/books?id=BzAEAAAAMBAJ&q=infoworld+1982+hercules&pg=PA77}}</ref>

The video output is 5&nbsp;V [[Transistor–transistor logic|TTL]], as with the MDA card.<ref name="nemesis">{{cite web |title=IBM PC-Compatible EGA Video Reference |url=http://nemesis.lonestar.org/reference/video/ega.html |access-date=2007-08-22 |archive-url=https://web.archive.org/web/20140511072035/http://nemesis.lonestar.org/reference/video/ega.html |archive-date=2014-05-11 |url-status=dead}} 070822 nemesis.lonestar.org</ref><ref name="ports">{{Cite web |last=White |first=Ray |date=2004 |title=Monitor Ports - Obsolete Interfaces |url=https://whitefiles.org/b1_s/1_free_guides/fg1mt/pgs/h10f.htm |website=Technology Guides|archive-url=https://web.archive.org/web/20170322001323/https://whitefiles.org/b1_s/1_free_guides/fg1mt/pgs/h10f.htm |archive-date=2017-03-22 }}</ref><ref>{{Cite web |date=2011 |title=PC video hardware page: Monitor connections |url=http://www.epanorama.net/links/pc_video.html#monitor |access-date=2023-04-13 |website=ePanorama.net|archive-url=https://web.archive.org/web/20170317051011/http://www.epanorama.net/links/pc_video.html#monitor |archive-date=2017-03-17 }}</ref> Nominally, the Hercules card provides a horizontal scanning frequency of 18.425&nbsp;±&nbsp;0.500&nbsp;kHz and 50&nbsp;Hz vertical.<ref name="industrial-monitors">{{cite web |title=Industrial monochrome monitors 7"–14" |url=http://www.adm-electronic.de/pdf/MNL115_ita_eng.pdf |url-status=dead |archive-url=https://web.archive.org/web/20070202201848/http://www.adm-electronic.de/pdf/MNL115_ita_eng.pdf |archive-date=2007-02-02}} 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.{{Citation needed|date=August 2020}}