Classic Mac (OS 8) screen resolution problems

Muzer

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Ages ago, I bought a Macintosh Performa 630 from someone on this very forum, but I declined to buy the monitor as well, as I thought I would just be able to use an adaptor. The other day, I finally got around to ordering this adaptor, and it arrived today. However, I have tried all of the DIP switch configurations in the manual, and nothing will produce a picture on my LCD.

I thought this was probably because the resolution might be set too high - the maximum on the adaptor is 1152x870, and I seem to remember the seller saying something about 1280x1024. So, my questions are:

* How do I reset the resolution using only the keyboard and no screen?
* What resolution will this give me?


Thanks in advance!
 

arnljot

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I don't have the answer for you.

But I know what I'd do :)

Having modern macs myself, and having had similar resolution problems I'd google for troubble shooting guide for that macs "firmware". Most macs have a series of incantations that can be done while booting which will reset lots of settings, such as screen resolution to lower default values.
 

AndyLandy

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If in doubt, hold down Command-Option-P-R on boot. That'll zap the PRAM and should drop the boot resolution back to 640x480. Hold the keys as you power on. The Mac will chime once and reboot. Once it chimes a second time, you can let go.

If you're using a TFT, it'll probably have a native resolution of say 1280x1024, but most will display something at lower resolutions, even if it looks blocky and horrid.

What adapter do you have? Some have more DIP switches than others. The one I used to use was a six-switch model. It worked in VGA modes with switches 3 and 4 on and the others off (It might be the absolute inverse of that, but certainly switches 3 and 4 were one way and the other four were the other way.)

Hope some of that helps!
 

TheoryBoy

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There are two things here that come to mind.

1. Flat PRAM battery, this can usually be tested by reseting the performa from the keyboard : Command-Control-Power , the mac should bong and detect the monitor.


2. Monitor settings and refresh. The performa is able to detect SVGA monitor types so if you adaptor lists that then use that setting. You could also try "Apple Multiple Scan 14" as that is what a lot of the performas came with.

Once you can get video, you can try other monitor types
 

Justin

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now now, play nice!

you know BINs are allowed

so play nice and help your fellow bayers

remember this me old fruit "don't let the bar stewards drag you down"

cheers buddy, JuvUK


where did this post by Tokyo go?

"More then likely it's your battery my friend, there's loads of 1/2 AA (3.6v) on the feeBay. Sadly I can't link (even BIN's) since everything is considerd "pricedriving" these days. :roll:"
 
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bazzaq

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I agree with previous posts.. gotta replace the battery, almost certainly..

Most of these vga convertors have a refresh rate config too.. Make sure your lcd supports the refresh rate as well as the resolution.
 

Muzer

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There are two things here that come to mind.

1. Flat PRAM battery, this can usually be tested by reseting the performa from the keyboard : Command-Control-Power , the mac should bong and detect the monitor.


2. Monitor settings and refresh. The performa is able to detect SVGA monitor types so if you adaptor lists that then use that setting. You could also try "Apple Multiple Scan 14" as that is what a lot of the performas came with.

Once you can get video, you can try other monitor types

Thank you very much. I pressed command - control - power and it reset. I then started changing the DIP switches to Multiple Scan 14", and it actually started working before I had finished setting them. Then, oddly enough, when I finished setting them it broke again. I don't believe the current setting is actually in the manual at all, but it works, so I'm not complaining ;)

In case anyone else is interested: the config I'm using is 1456789 on, the rest, off (I have a 10-switch model)

---------- Post added at 18:56 ---------- Previous post was at 18:31 ----------

Right, now even when I set it to the "standard" modes, I can't get 800x600 (which is the only other resolution listed... odd.)
 

TheoryBoy

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Cool, Apple monitor id detection only happens at boot time, so changing the setting while powered on might do anything (although some re-detection happens at driver load time during extensions)

But if you select AppleVision/ColorSync 750 as your monitor type it will open up a few more resolutions and keep the refresh rate low enough for your monitor to sync.
 

Muzer

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I've managed to get it in 832x624, BUT the picture is very far to the right of the screen even with H-POS at 0. 640x480 it is then...
 
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