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Path: utzoo!mnetor!uunet!seismo!rochester!cornell!uw-beaver!tektronix!tekcrl!tekfdi!videovax!stever
From: stever@videovax.Tek.COM (Steven E. Rice, P.E.)
Newsgroups: comp.sys.amiga
Subject: Re: Possible new hack
Message-ID: <4494@videovax.Tek.COM>
Date: Wed, 15-Jul-87 11:10:38 EDT
Article-I.D.: videovax.4494
Posted: Wed Jul 15 11:10:38 1987
Date-Received: Sat, 18-Jul-87 04:03:50 EDT
References: <1699@amiga.amiga.UUCP>
Reply-To: stever@videovax.Tek.COM (Steven E. Rice, P.E.)
Distribution: na
Organization: Tektronix Television Systems, Beaverton, Oregon
Lines: 36

In article <1699@amiga.amiga.UUCP>, Dale Luck (dale@amiga.UUCP) writes:

> For you guys that need 120 hz refresh but can get by with half the number
> of lines are your display, you could try this.
> I haven't tried this out , but it shoudl work.
> Write the beam counter in the middle of the display to bump it down
> to the end. I don't remember if the copper can write the beam counter,
> the chip designers might have gone crazy again with their arbitrary
> limitations. But anyway, write it so it is about 255 or so, it will then
> continue counting up to 262 or so and trigger vblank and the display
> will start again. Most monitors should not have any trouble with this.
> Well, I'm no hardware guy so that is just a guess to.

No luck, Dale!  Most monitors will ignore a vertical interval in the
middle of the active picture area.  Those that don't will have a fit
trying to synchronize to something that is twice normal rate.  (The
deflection magnetics are usually resonated at the scan rate to reduce
drive power requirements.)

> This response prompted by some guy in toronto wanting to quad lace
> the display. I remember the tektronics stereo displays were running at
                              ^^^^^^^^^^
Aaaaaarrrrggggggghhhhhh!!!!!  That's TEKTRONIX!!!  No "c"s.  No "s"s.

> twice refresh rate so this idea just popped up. Meaning they were
> interlacing at 120 instead of 60hz per field.

Special monitors.  Big bucks.  Not interlaced -- progressive scan (how
progressive!).  Since the liquid crystal light valve can switch
polarization between frames, every other frame is a "left eye" frame.

					Steve Rice

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