This is just an FYI for anyone who might search our archives for something about getting a IIci or IIsi to work with a VGA monitor.
I spent all day Sunday last week searching the web for articles or postings on the web from anyone who had successfully connected a IIci to a VGA monitor. Specifically I was looking for DIP switch settings for a generic 10-switch Mac-VGA adaptor.
First, it took me forever just to find any webpages that had DIP switch settings at all. Then, it took forever to find any of those webpages that even mentioned the IIci. And unfortunately, every time the IIci was mentioned, it just said what I already know: the IIci can't drive a VGA monitor, and its not very often that a Mac to VGA adaptor will change that.
All the while I was experimenting with different settings on the IIci. BTW, I know they almost always say that you should shut down, change the DIP switch setting, then reboot to see if it works, but I've never had to. I just change the settings on the fly and see if the screen comes up.
That's what I did while I was experimenting, and finally I came across a couple of settings by accident that worked with two of my monitors. I got them using a generic 10-switch adaptor I got from MacWarehouse. There are also 9-, 8- and 6-switch adaptors out there. I briefly experimented with a 9-switch adaptor but got nowhere, I think because the adaptor couldn't deliver sync-on-green. I think I've read that that is what a IIci needs to sync with a VGA monitor.
Anyway, on a 10-switch adaptor, I got a generic 15" MacWarehouse-brand monitor to work with switches 1, 4, 5, and 8 turned on, the rest off. I also got a 21" Sony monitor to work with 1-4-5-8, and also 1, 4, 6, 7 and 8. Curiously, the 1-4-6-7-8 did not work with the 15".
I see no reason why these settings wouldn't work with a IIsi too. Of course, I have to give the standard YMMV disclaimer, considering that there may be differences between some generic 10-switch adaptors that I don't know about, and of course monitors always have their own differences.
IIsis and IIcis are basically the same in video output. They both combine the Horizontal and Vertical Sync on the Green Video line (Sync-on-Green). They do not provide discrete sync signals. Only a few models of VGA monitor were built with Sync-on-Green capabilities (in addition to discrete sync). They were made to work with Macs or PCs which at the time was rare. Since later Macs could work with discrete sync the Sync-on-Green monitors are very small in number.
I have no reason to believe that the switch operation on two adapters with the same number of switches but from different manufacturers would be the same, or even close except that they do more or less the same thing. Ie. that the switch settings for one adapter would apply to another brand adapter.
There is an adapter from Griffin Technologies that will generate discrete sync from Sync-on-Green but as these are more expensive than a monitor (last I looked) it's not a very practical solution.
Yes, you can change the sync signal settings and not need to restart. A restart is only necessary if you change the video coding telling the computer what type of monitor is attached. Since the options here for a IIci or IIsi are rather limited you likely wouldn't be changing those settings.
--
Clark Martin
Redwood City, CA, USA
Macintosh / Internet Consulting
"I'm a designated driver on the Information Super Highway"
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