Color Classic Resolution Switching

[JDW]

I am currently filming a new video about the Apple IIe Card in my Color Classic Mystic. As many of you know, I performed the VGA mod on this CC earlier this year, which boost the stock resolution of 512x384 to 640x480. Smaller pixels means everything is smaller, but the upside is you can run many games and other apps which require VGA as the minimum resolution. Even so, aging eyes line mine prefer larger pixels, and I always thought it would be neat if we could switch back to the stock 512x384 on the fly.

One thing I have learned in my testing of the Apple IIe Card is that it switches the CRT screen resolution to 560x384, regardless of whether you have the stock 512x384 or the 640x480 mod! The IIe Card proves it is possible to switch resolutions without having to hack anything on the hardware side. I don't think the IIe Card has any video control circuitry on it, and instead it is just sending some kind of command to the Mac to perform the resolution switching. Would any of you know if that command is something hard coded in ROM?

I'm just trying to brainstorm about whether it is possible to use the same trick to alter the resolution to something else, such as going from 640x480 to 512x384 and back. It would be SUPER NEAT if that was possible!

 

[mg.man]

such as going from 640x480 to 512x384 and back.

...or what about going to 560x384 in "Mac" mode? That might be more doable - since the h/w has been modded for 640x480? I assume the Apple IIe mode is stable with the VGA mod in place?

 

[JDW]

...or what about going to 560x384 in "Mac" mode? That might be more doable - since the h/w has been modded for 640x480? I assume the Apple IIe mode is stable with the VGA mod in place?

It is stable, yes. It looks as perfect with the VGA mod as without. I never tested my machine with the IIe Card in the stock resolution, but when I find screenshots online of the stock resolution CC using the IIe Card, it looks identical to mine with the VGA mod in place. Again, this is proving that the IIe Card is ignoring what resolution is set in the hardware (on the Analog Board) and is forcing a particular resolution (560x384) to display on the CRT. This is why I said, if that is possible (and we know it is), then it should be possible for us to manipulate the resolution in the same way. I just don't know how, on the technical side, hence my opening post.

 

[mg.man]

I never tested my machine with the IIe Card in the stock resolution

That begs an interesting question... if you're correct that the Apple IIe card forces 560x384, then that would mean it's "boosting" the resolution of a stock CC. Are you sure it's not just a case of the CC analog board having the ability to sync on the 'lower' Apple IIe resolution? How have you come to the conclusion the IIe output resolution is 560x384?

 

[JDW]

How have you come to the conclusion the IIe output resolution is 560x384?

ANSWER: this Apple technical document
(Side note: I have the standard VGA mod which retains the 60Hz refresh rate. Not sure what happens if you use the other VGA mod which uses 67Hz.)

For even more detailed info, start watching this video until about the 13:00 mark. He shows both the LC and the Color Classic.

 

[mg.man]

Cool, THANKS for those! I was wondering about the LC.

I do have a IIe card in my CC II, and I do have a LC575 'board, so have been toying with doing the VGA mod. Good to know I won't lose IIe capability.

I'm still curious as to whether or not MacOS could access this 560x384 mode without alteration...

 

[JDW]

I'm still curious as to whether or not MacOS could access this 560x384 mode without alteration...

No because as 8-bit guy points out, the Mac requires SQUARE pixels and using 560 would not keep them square.

 

[mg.man]

the Mac requires SQUARE pixels

I don't think it's "required", more 'designed-for'. Example, you can run MacOS on a Lisa - but it looks a little odd because the Lisa does not natively have "square" pixels. For the Macintosh XL, there was a "square pixel" mod to correct this. My point is, it should 'work', but it may not look right.

 

[JDW]

I don't think it's "required", more 'designed-for'. Example, you can run MacOS on a Lisa - but it looks a little odd because the Lisa does not natively have "square" pixels. For the Macintosh XL, there was a "square pixel" mod to correct this. My point is, it should 'work', but it may not look right.

But if 560x384 isn't a supported resolution in MacOS, would it even work? Not sure. Maybe not.

Mac on Lisa works, I assume, because it is something supported by the Lisa, right?

Regardless, we need to know how the resolution switching on the Mac is done in order to know if it's possible to swap between VGA and the stock CC resolution. I suppose other resolutions like 560 or even higher resolutions than VGA could work too, but in my testing anything higher than VGA on the CC's CRT is too small and grainy to be usable.

All said, I personally want a switch (either software or a mechanical toggle switch) to flip between the stock CC resolution and VGA. That would satisfy me just fine!

 

[mg.man]

Mac on Lisa works, I assume, because it is something supported by the Lisa, right?

there's 'bootstrap' code in the form of MacWorks by Sun Remarketing. Perhaps that 'patches' the underlying ROM functions to add the Lisa resolution?

we need to know how the resolution switching on the Mac is done

Do you mean CC? Regardless, I'm now curious what happens when going from LC 640x480 to "IIe" mode [560x384?] with an external monitor - esp. a flat panel LCD. I think I'll pull my IIe card and pop it in my LC and hook that up and see what happens - never tried.

 

[JDW]

Do you mean CC?

Yes, I don't own any LC machines. I only have a Color Classic Mystic.

 

[mg.man]

I don't own any LC machines.

Stay tuned... will let you know what I find.

Also curious to hear from the gurus States-side once they're 'd up and online...

 

[JDW]

I especially want to hear from a Color Classic owner who also owns the IIe Card and who has done the high-voltage VGA mod, which changes the refresh to 67Hz. I suspect resolution switching even in that case would work fine, but that isn't something I've tested.

 

[mg.man]

will let you know what I find.

OK, so... on my LC II, when running in IIe mode, the resolution is NOT changed - the LC II keeps the output at 640x480 @ 67hz. So "switching" seems to be a "CC" phenomena?

 

[mg.man]

Just remembered... the "LC" supports 512x384... I do have a LC, but not sure I have a working CRT that will work at that rez (don't think my LCD will?). I'll see if I can explore that path...

 

[JDW]

I cannot comment on the LC except to say that typically the Apple 12" RGB Display is used with them, and that display has a native resolution of 512x384. So it seems you have something other than the 12" display. Regardless, I'd love to see a photo of your display when the IIe Card is in the IIe environment.

 

[mg.man]

I'd love to see a photo of your display when the IIe Card is in the IIe environment.

I don't have anything on the LCII to load atm... must get the TotalReplay image...

 

[mg.man]

Haven't had the chance / energy to do a full Total Replay / ProDos partition set up on the LC II, but I did connect my FloppyEMU in SmartPort HD mode with the bundled FE image from BMOW...

No resolution switch... the output stays 640x480 @ 66.7Hz

 

[JDW]

No resolution switch... the output stays 640x480 @ 66.7Hz

But in your first screen photo, I am not noticing anything being chopped off or truncated or pixel-distorted. It looks exactly like it should when the resolution is set to 560x384. If it was displaying in something other than 560x384 mode, I would expect some kind of distortion. But again, I am not seeing that in your first photo.

 

[mg.man]

The "Mac" screen displays edge to edge of rhe monitor, the IIe display has borders. So I'm guessing the IIe "560x384" is just 'padded out all 'round.