LC 575 Monitor Resolution

[LC_575]

Is it possible to set the screen resolution of a 575 to something higher that 640x480?

 

[Gorgonops]

Not to my knowledge. If you Google there are vague hints that people have hacked the monitors in the 68k-era AIO Macs to support 800x600 at a very low (think eye-burn) refresh rate, but a quick look failed to turn up any instructions. (My guess is that it would a similar process to hacking a CC from 512x384, IE, modding the wiring harness to change the sense line information and futzing with a few resistor values in the monitor to permanently change it to the new fixed resolution.)

 

[techknight]

800x600 you could still get within the lock range of the vertical ramp oscillator circuit with some adjusting.

The horizontal however, you would have to almost change out the R/C time constant in the horizontal oscillator circuitry to be able to lock it in. The lock range depends on the particular IC used, but it can only deviate so far in either direction above or below the center frequency of the PLL/Oscillator. It is the job of the hold controls to adjust the locking point, but sometimes this can go "out of range"

 

[LC_575]

So this isn't something I can do with an extension then? I'm not really interested in hardware hacking around high-voltage capacitors.

 

[techknight]

not without hacks, no. maybe if you used an external monitor that supported it, then you could probably get away with a software hack. Then it becomes a question of available VRAM.

 

[Bunsen]

I'm almost sure I've read of someone pulling it off with the existing hardware, but yes, it involves hardware hacking, not software.

 

[Byrd]

I'd trawl through the Colour Classic forum over at Applefritter - like others, I have read about a similar hardware modification to the LC575 analogue board to run @ 800 x 600. Not sure if the 575 motherboard could "take" this though; it was more for a Takky-upgraded Colour Classic with a LC575 analogue board in place of the stock one.

JB

 

[Bunsen]

The analog board from a 575 has been used in Colour Classic hacks to reach 800x600 - but that's a different CRT assembly altogether. Whether it can be achieved in the 575 itself is another question.

http://www.applefritter.com/node/5200

This CC hacker tried both a 575 analog board and one from a Macintosh Color Display (M1212)

http://www.applefritter.com/node/6942

Further clues:

http://www.applefritter.com/node/4801

http://www.applefritter.com/cgi-bin/YaBB/YaBB.pl?board=powercc;action=display;num=1071502305

http://www.applefritter.com/cgi-bin/YaBB/YaBB.pl?board=powercc;action=display;num=1045165303

http://www.applefritter.com/cgi-bin/YaBB/YaBB.pl?board=powercc;action=display;num=1042249830

 

[Bunsen]

800 x 600. Not sure if the 575 motherboard could "take" this though

Good question. A first test would be to attach a second monitor on the (optional) video mirroring port, disconnect the internal monitor and see if the logic board can drive the external @ 800x600 (or indeed any other resolution). If that fails you might need an LC PDS video card.

 

[LC_575]

A first test would be to attach a second monitor on the (optional) video mirroring port, disconnect the internal monitor and see if the logic board can drive the external @ 800x600 (or indeed any other resolution). If that fails you might need an LC PDS video card.

How would one go about doing this?

 

[Gorgonops]

A first test would be to attach a second monitor on the (optional) video mirroring port, disconnect the internal monitor and see if the logic board can drive the external @ 800x600 (or indeed any other resolution). If that fails you might need an LC PDS video card.

Many apologies if I'm wrong with either of these statements, but... a couple points there:

A: Isn't the only "video mirror port" available for the 575 a rare third-party device that hackishly pressed on top of the video chip? and...

B: I may be completely misremembering this, but aren't all the monitor lines part of the big nasty connector that the whole motherboard plugs into in the front of the case? That being the case the only way to "disconnect" the internal monitor would seem to be to cut up the internal wiring harness, or at least fiddle with the edge connector. Even if you were to disconnect the wiring at the Analog Board end, if you can do that cleanly, you'd still need to muck with the sense lines in the harness to let the Mac set other resolutions.

EDIT: BTW, if you Google around you'll find passing references in forum threads to people getting 800x600 out of LC 575 boards plugged into "Mystic" Color Classics when the harness has been modded for VGA. (Remember, "Takky" was the radical harness swap operations with a 5200+ series box.) So it's probably safe to say that going to weird lengths to "prove" that the motherboard is capable is unnecessary.

How would one go about doing this?

I think the short answer is you don't want to try, and if you want a higher-res Mac otherwise like your 575 you'd be much better off buying an LC 475 or Quadra 605 and pairing it with a nice Multisync monitor. A monitor stacked on an LC case takes the same space, basically.

Otherwise, if you want to hack up your 575 your best bet appears to be to see if archive.org still has copies of the Japanese-language websites which fully documented the wiring harnesses in Color Classics, and follow the instructions to enable "VGA mode". (It's unfortunate, but a simple "google" doesn't seem to turn up anything but piles of dead links.) The 575 has the same wiring harness and the sense-line setting for "VGA" will unlock the ability to play with arbitrary video modes on the motherboard side. The only difference is that yours will have different settings to start with, since the mode the CC was locked into was 512x384. (Wild guess, but I imagine the sense line setting for the LC575 matches that for a "Hi-Res" monitor while the CC matches "RGB 12".) You'll just have to remember that without drastically fiddling with its settings or changing component values the only mode the monitor is *designed* to accept and display properly is 640x480@67hz. If you had the wiring diagram you could possibly cut the correct lines and wire a VGA plug to them to disable or mirror the internal, but... do you really want to do all that?

Eh, go for it if you're up to it.

 

[LC_575]

Oh, I'm already overwhelmed. Maybe I just need to clean up my desktop to make the screen look bigger...

 

[Bunsen]

A: Isn't the only "video mirror port" available for the 575 a rare third-party device that hackishly pressed on top of the video chip?

AFAIR, and I was checking one out on ebay recently, it's an Apple part (of that I'm pretty certain) though there may have been third parties as well, and there's a slot set aside for it (not 100% certain).

Point B seems correct.

if you Google around you'll find passing references in forum threads to people getting 800x600 out of LC 575 boards plugged into "Mystic" Color Classics

Yeah, I linked those I could find above.

when the harness has been modded for VGA

Yes, that's the crucial point. These were people who had already taken the plunge into wiring harness mods.

an LC 475 or Quadra 605 and pairing it with a nice Multisync monitor.

Course, you could stick that into the 575 case if you wanted } Again, much hackery involved, but it would be the relatively simple case (heh) of making room and mountings for a known-working system inside the 575, rather than mucking about with wiring and component mods to build a maybe-working system.

Opinions will of course differ as to whether this is a desirable thing to do to a working 68k. And, once you've gone that far, you might as well go the whole hog and Mini/LCD it.

Hmm, Bunsen looks suspiciously at 575 case and Quicksilver motherboard.

 

[Gorgonops]

A: Isn't the only "video mirror port" available for the 575 a rare third-party device that hackishly pressed on top of the video chip?

AFAIR, and I was checking one out on ebay recently, it's an Apple part (of that I'm pretty certain) though there may have been third parties as well, and there's a slot set aside for it (not 100% certain).

The only reference to an output port I could find for the 575 was for a device called the "Presenter 575" that some sites say was a product of a company called "Power R" while other sites call it an Apple product. They're probably the same thing. In either case they seem to have been a *very* niche product aimed at hooking the Mac up to a projector or other large screen.

 

[Bunsen]

It's possible I am thinking of something for the later PPC Performa AIOs

 

[LCGuy]

You might be thinking of the "Apple External Video Connector" which actually was a video output solution made by Apple for the 5x00 series AIOs. I don't ever remember Apple doing anything for the 68k AIOs (with the exception of the LC/Performa 580 which had the slot for the Apple External Video Connector), there were just the third party options.

 

[Bunsen]

Yep, that sounds like it. Pardon my confuzzlement.

 

[uniserver]

google brought me back here.. lol this forum is king!

this guy said he got 800x600 on his LC575

http://mail-index.netbsd.org/port-mac68k/1999/06/13/0014.html

 

[beachycove]

Pop an LCPDS video card in, or pop the right one in at any rate, and you can drive a two page display in thousands of colours and with extended desktop. One advantage of the LC575 in this respect is that it takes a Comm Slot 1 ethernet card, so you won't lose networking if you go this route.

Most of these cards are seemingly not especially good by comparison with high-end Nubus cards, but I think that Focus Enhancements made one that was accelerated. Tracking down drivers might be an even greater pain than finding the card, however, as they are exceedingly rare.