At 11:28 AM -0500 8/23/99, James Sentman wrote:
>This brings up another question. Most of the past year I've spent at
>a client location with my 2400 connected to an external monitor and
>keyboard. The monitor they gave me was a 17 gateway thing. Perfectly
>ok. BUT when it was plugged into my 2400 and you hit the monitor
>control strip, the first line correctly displayed the model and
>number of the monitor!
>
>I understand that the reason Apples monitor connectors are larger
>than standard VGA connectors is because they contain "sense pins"
>that allow the Mac to know what resolutions the monitor supports. But
>in this case there is only a standard VGA connector with none of that
>voodoo, and Gateway sure doesn't support apple sense technology.
>
>How in heck does my 2400 know the model number of the monitor it was
>connected to?
Well, to start out with, there actually aren't any more pins in the Apple
connector than there are in the PC VGA connector. Both have 15 pins; the
VGA is smaller because it uses three rows of pins instead of two. The only
reason for the Apple connector is that I think VGA wasn't defined yet when
Apple invented their own. I do wish it hadn't taken them so long to adopt
the VGA connector, though.
That's especially true because over the past several years (5 or so, I
think), the PC has actually had a far superior monitor sensing system,
using the same-old VGA connector. Not all the pins were used, so the Video
Electronics Standards Organization (VESA) decided to use some for a sense
system, DDC. Basically DDC is a serial bus, which allows the computer to
get essentially unlimited information from the monitor, including its name.
By contrast, the Mac monitor sense system is basically three pins on the
connector which are shorted together in different combinations to tell the
Mac which of several Apple-defined monitor types is connected. This system
is quite limited, so Apple eventually decided to adopt DDC too.
Tim Seufert
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