Editing VGA connector (section)

=== PS/2 signaling ===
In the original IBM VGA implementation, refresh rates were limited to two vertical (60 and 70&nbsp;Hz) {{dubious-span|reason=this claim does not seem to be in the cited source (though I would not exclude the possibility OP may have misread the source, or if I'm misreading it, tell me how); claim originally added here: https://en.wikipedia.org/w/index.php?title=VGA_connector&diff=prev&oldid=973364678|and three horizontal|date=May 2024}} frequencies, <span class="cleanup-needed-content" style="padding-left:0.1em; padding-right:0.1em; color:var( --color-emphasized, #595959 ); border:1px solid #DDD;">all of</span> which were communicated to the monitor using combinations of different polarity H and V sync signals.<ref name="IBM PS/2">{{Cite book |url=http://classiccomputers.info/down/IBM_PS2/documents/PS2_Hardware_Interface_Technical_Reference_May88.pdf#page=492 |title=IBM Personal System/2 Hardware Interface Technical Reference |chapter=Video Subsystem (Type 1) |pages=13.99–13.100 |archive-url=https://web.archive.org/web/20180514201314/http://classiccomputers.info/down/IBM_PS2/documents/PS2_Hardware_Interface_Technical_Reference_May88.pdf#page=492 |edition=First |publisher=[[IBM]] |date=May 1988 |archive-date=14 May 2018 |access-date=16 February 2021}}</ref>

Some pins on the connector were also different: pin 9 was keyed by plugging the female connector hole, and four pins carried the monitor ID.<ref name="IBM PS/2" />

With the implementation of the VESA DDC specification, several of the monitor ID pins were reassigned for use by DDC signaling, and the key pin was replaced with a +5&nbsp;V DC output per the DDC spec. Devices that comply with the DDC host system standard provide {{nowrap|5 V ± 5%}}, from 50{{nbsp}}mA to 1{{nbsp}}A.<ref>{{Cite book |title=VESA Enhanced Display Data Channel Standard Version 1.1 |publisher=[[Video Electronics Standards Association]] |date=24 March 2004 |page=18}}</ref>