

Here's the story:

(1)  The IIsi *cannot* supply a VGA output.  However...

(2) Some VGA-type monitors can adequately deal with the video signal
the Mac uses to drive the Apple 13 or 14 inch "high resolution color
display"---i.e., Apple's own 640x480 mode.

So, if you wish to hook one of these monitors up to your IIsi, you
need (a) an adapter that converts from the Mac DB-15 connector to the
VGA-style high density DB-15 connector, *but* tells the Mac to use
it's own 640x480 mode, not the VGA 640x480 mode, and (b) a VGA monitor
that can deal with the higher bandwidth of the Mac 640x480 mode over
the VGA 640x480 mode (which as I stated in (1) above, the IIsi cannot
produce).

As far as (a) above is concerned, contact

 James Engineering, Inc.
 6329 Fairmount Ave.
 El Cerrito, CA  94530
 510-525-7350
 FAX: 510-525-5740

They can probably get you the right adapter.  Remember: you do *not*
want the run-of-the-mill Mac-to-VGA adapter, because it will try to
have your IIsi produce the VGA mode, which it cannot (the computer
will just fail to produce any video signal at all).  Instead, you want
an adapter that connects between the Mac-style and VGA-style
connectors, but tells the Mac to use the Apple 640x480 mode.  Sorry
for the poor terminology available for describing this distinction.

As far as (b) is concerned, make sure to get a monitor that can deal
with a horizontal bandwidth of 35 KHz and a vertical retrace rate of
67 Hz.  These are the spec's of Apple's 640x480 mode.  For comparison,
the VGA-standard 640x480 mode uses a 31.5 KHz horizontal bandwidth and
a 60 Hz. vertical retrace rate.

The monitor will probably need to have auto-synch'ing capability, as
the Apple mode you'll be using isn't one of the set of standard modes
in the PC compatible world.

Good luck!

	-Fred Martin

