[rescue] Re: SGI Video - PC Monitor (*)

[Jonathan C. Patschke]

On Thu, 28 Mar 2002, Eric Webb wrote:
> I have a 13W3 -> HD15 borrowed from an RS/6K box.  The cable is good because 
> it works on my SS20.

The SS20 does not do syncs in the same way that the SGI does.  But, since
it's an RS/6000 cable, it's probably not doing anything weird with the
sync signals, as RS/6000s are SOG (I think).

> However, my 19" SVGA won't display anything.  It's reporting 0khz
> horizontal and 72.2khz vertical.  This tells me that the hsync line is
> either grounded or not connected and the vsync line probably is 
> connected.

Actually, it's more complicated than that.  All syncing is done over the
green line on an SGI.  However, the SGI has either grounded the hsync pin,
or it sending monitor ID requests over what would be the hsync pin.

The sync-binding happens on the SGI gfx card, so it's not that the cable
is wired incorrectly or that the cable is supposed to break those signals
off.

> Now, this tube is an Envision EN-910e.  Certainly not top of the line, so it 
> wouldn't surprise me if it doesn't do SOG, but I can't definately say that it 
> doesn't.  (Anyone have one?)

If it's getting vsync, it does SOG, as the vsync is sent on the green pin.
Hsync is send on there also, but if the hsync pin looks weird, your
monitor might be ignoring the hysnc component of the green pin.

> Would it perhaps help to craft a cable/adapter that doesn't connect the sync 
> lines just in case they are the source of the confusion?

Yes.  See below

> Maybe my 13W3->HD15 is wrong/bad?  I have a scope, can anyone tell me
> what I'm looking for?

Here's the fix: pull all the pins out of the 13W3 connector.  Leave the
three coax connectors.  Problem: it won't work on the SS20 anymore, as the
SS20 uses composite sync.  Solution:

[sgi]<---extension cable---><---13w3-to-HD15--->[monitor]

Pull all the small pins off one (or both) ends of the extension cable.  
Do not modify your 13w3->HD15 cable.  This way, you can use the extension
cable to float all the pins so that they won't confuse your monitor when
talking to your SS20, but you can still use the 13w3->HD15 to talk to your
SS20.  This works great on my IBM P200 monitor at home.

--Jonathan