Re: Using a IIgs monitor on a Mac LC II?

[dempson@actrix.gen.nz (David Empson)]

william strutts <wrstrutts1@nospam.home.com> wrote:

> "Tim Haynes" <trhaynes@yahoo.SPAMBGONE.com> wrote in message
> news:QvLB7.73928$YL3.20306577@news3.rdc1.on.home.com...
> >
> > As soon as I saw it, I thought, "Hey, a Mac LC II for $5!  Those things
> > can run IIe emulator cards!"  However, when I got it home and hooked up
> > an RGB monitor from one of my IIgs's to it, it looked like the display
> > was heavily out of synch.
> >
> > Am I out of luck in terms of getting a IIgs RGB monitor working on this,
> > or is the RGB monitor that I tried (the only one I had quickly at hand,
> > and one I've never tried before) fried?
> 
> It won't sync to a IIgs montior. Its refresh rate is much higher
> like 33mhz or 60 mhz. I don't recall exactly. However, the IIgs
> refresh rate is like 15.7 mhz or something like that.

I assume you meant "MHz" (megahertz).  "mhz" isn't a valid unit (it
suggests millihertz, i.e. thousandths of a Hertz, but the "h" is
supposed to be capitalised as well).  :-)

In any case, you were out by a factor of 1000: the relevant numbers are
in kilohertz, not megahertz.  These numbers refer to the horizontal scan
frequency, i.e. the total number of scan lines displayed per second.

The IIgs outputs video at NTSC-compatible TV frequencies (about 15.75
kHz), and this is what the IIgs RGB monitor expects.

The LC and other Macs output video at VGA-like frequencies, which is at
least 30 kHz (60 Hz vertical retrace, multiplied by about 500 scan
lines).