Scene Double 25pin-15pin SVGA

The guys at Scene Double are very helpful - we use a lot of their extenders for sending SVGA a long way and we had to make up a replacement 25 pin (D) - 15 pin (HD) cable. I emailed Ray;

I wondered if you could let us have the pinouts so I can quickly knock them up a new cable.

He replied with suitable engineering forthrightness!

I would not advise knocking up cables with mini coax.

Job done!

You down with DDC (Yeah you know me)

Display Data Channel is the way both analogue (i.e. SVGA) and digital (DVI) computer monitors communicate back to their graphics cards what their abilities are - what resolutons they can run at and what refresh rates. Additionally the monitor will send it's name so that the driver can load colour correction lookups etc.
Now, Scene Double (link above) are my favorite KVM extenders - I've banged on about them before (see here) and they now have a very cute trick where the extender can back-propogate the DDC data from the monitor - very useful particularly when extending Mac monitors (where you can't force generic monitors like you can under Windows). Now, Ray Gordon - the lead engineer at Scene Double helped me through a problem today - I had a MacPro being extended over cat5 to a Dell 2407 monitor. The Graphics card (nVidia FX4500 - so no slouch!) refused to drive the monitor at anything above 1920x1080 even though the Dell's native res is 1920x1200. It transpires that OS-X has a problem that relates to the underlying X11 (Apple version of Xfree86) graphics engine which caches the DDC data from the first display on the card. If it has had a sniff of a different monitor (or the same monitor fed over DVI) it won't allow you to set a different resolution/refresh rate and have it stick through a reboot. The answer is on single monitor systems to hang the extender off the 2nd o/p - then it's all good!

Wow - I always maintained that I'd never extend VGA feeds over cat5 cable. I've tried maybe a dozen units over the last few years and they always seem adequate for a sys op to dive in and do five minutes on the server (creating an account etc.) but never good enough to drive monitors at hi-res that someone has to look at all day (in an edit suite for example). They all look smeary and soft.
Scene Double have a range that works splendidly - they use skew compensation (and in fact you get a whole host of LF and HF adjustments) to make the picture spot on - even at 1280x1024 over 50m of cable. I'm a believer! (I've just installed eight sets - they ain't cheap though - £899 a set).