Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!rutgers!bagate!cbmvax!raible
From: raible@cbmvax.commodore.com (Bob Raible - LSI Design)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: NEC 2A question
Message-ID: <16335@cbmvax.commodore.com>
Date: 6 Dec 90 04:08:26 GMT
References: <1990Dec5.155357.3957@intelhf.hf.intel.com>
Reply-To: raible@cbmvax.commodore.com (Bob Raible - LSI Design)
Organization: Commodore, West Chester, PA
Lines: 33

In article <1990Dec5.155357.3957@intelhf.hf.intel.com> griff@anvil.intel.com (Richard Griffith) writes:
>How difficult is it to hook up a NEC Multisync 2A to a 2000?
>anyone know? (awww, comeon, someone here knows... :-)                   
>               
>                       - griff
>
>:Richard E. Griffith, "griff" : iNTEL, Hillsboro Ore.
>:griff@anvil.hf.intel.com
>:SCA!: Cyrus Hammerhand, Household of the Golden Wolf, Dragons' Mist, An Tir 
>:These are MY opinions, if iNTEL wanted them, They'd pay for `em!

I currently use this combination at work. As you note I am a chip
designer and not  an official spokesman for this type of thing, so I am
not certain as to what the "official" advice is. What I have noted is
that if productivity mode operation is desired(when 2.0 is available to
2000 owners) then it is necessary to use separate syncs and not the
CSYNC signal. However during boot phase HSYNC and VSYNC outputs are
momentarily tri-stated and checked for the presence of an external
source of syncs(genlock). However presence of 75ohm pulldowns on NEC2A
sync inputs, the levels are less than ideal and the software wrongly
concludes that an external device is trying to supply syncs and will
provide synchronized 28MHz as well. Consequently the internal 28MHz
clock is disconnected and the system hangs.

The upshot of the above discussion is that ideally the hsync and vsync
signals will be buffered before being connected to monitors having 75ohm
terminations. Typically a TTL buffer is wired into the hood of the
B2000 video connector. The other alternative is to use CSYNC instead,
but as mentioned above, CSYNC won't be available when using any of the
new ECS programmable modes(640x400,1280x200 noninterlaced).

Hope this helps - sure beats trying to figure out why your new monitor
keeps causing your 2000 to hang!