Subject: Re: VideoModes 101
To: Ezra Story <>
From: David Hopper <>
List: amiga-x
Date: 11/20/1995 23:37:59
> > My current resolution of choice is -MODE 9, which is undocumented
> > in any /etc/grfmodes that I've seen.  
> -mode 9?  -mode 9 is nonexistant in any device that uses grfconfig.  Xcl16
> may be using the default mode number when you specify 9.  Somehow,
> somewhere there has to be a grfmodes files loaded by grfconfig that has
> that mode defined.  There are no hardcoded modes in grf_cl.

You are absolutely right.  My mistake.  I had seen the mode definitions
run up to -MODE 12 in xserverrc.  That, though, is a leftover from
Xamiga24, and has nothing to do with Xcl.  When I specified -mode 9,
Xcl didn't tell me it was nonexistant; it went ahead and used the first
mode in my grfmodes file, which was -mode 1.  Looking at mode 1, I realize
that that's the great mode I had been using all along:

81000000 1152 900  8 145 155 167 169 178 905 910 914 930 940
(NetBSD 1.0A values)

> > First question:  using the methods described in VideoModes.doc, I
> > calculate that the mode I'm _currently using_ is impossible.  Xcl-alpha
> > is being driven at -memclock 65MHz (the default); thus we get the
> > following:
> Thats the memory clock, not the pixel clock.. which is entirely different.
" dope."  Come on, I know you want to say it...  Anyway, sorry for my
misunderstanding on this point.  All the more reason for a FAQ, I think.

Given that I have 40ns DRAM on my Picasso II, what are the benefits of
cranking up my memclock from 65 MHz to 70 MHz?  It does nothing for an
already-functional mode, right?  It just allows for greater pixel
clock values for new modes?

> [...]                                      For the cl5426 based boards,
> the only solution is to go into interlace (or parhaps push the board at
> 16bit.. but you're lucky if the display doesn't hash on you :-)).

This is a bummer.  I had hoped that I could get a fairly solid--if inter-
laced--display from the Picasso.  Now, I know that the Cybervision 
software under AmigaOS can create a sharp-looking 10x7 16-bit display
with barely a flicker; too bad we can't read the magic numbers that drive it.

> "grfconfig -r /dev/grf3" will list all the modes the device knows about
> in raw mode.

Thanks.  I knew this, but I had assumed that the mode I was using wasn't 
there, when it was all along.

> == Ezra Story -- -- Ezy@IRC -- ==

Thanks, everyone, for your help!