• Updated 2023-07-12: Hello, Guest! Welcome back, and be sure to check out this follow-up post about our outage a week or so ago.

Idea: Macintosh Classic III (LC550+M1420)

Johnnya101

Well-known member
Now this is the sort of thing I was thinking of in my "recreate a Mac" thread. It would be expensive, but imagine getting a new plastic case made, have a nice LCD display that "looks right", a new old logic board with upgrades... all brand new. Expensive, yes, but really cool.
 

alectrona2988

Well-known member
I was thinking more of a drop-in replacement for the Classic and Classic II systems that used a full 32-bit bus with the 68030 along with other add-ons so it won't just be another compromised mac. Unfortunately, I'm not too sure about the VGA mod, especially with an extra bench PSU hanging out the back. It's really cool, but I'm not sure how one could execute it while also making this more of an all-in-one solution.
 

Trash80toHP_Mini

NIGHT STALKER
Don't need bench PSU for 12" RGB LC topper resolution in grayscale that we're talking about. Standard A/B designs appear to be adequate for that. Going Retina Classic is quite another endeavor. ;)

Now this is the sort of thing I was thinking of in my "recreate a Mac" thread. It would be expensive, but imagine getting a new plastic case made, have a nice LCD display that "looks right", a new old logic board with upgrades... all brand new. Expensive, yes, but really cool.
Heh! That's already in the works, but injection mold tooling for the clear case is in storage for a second production run? with a little milling, the front bezel of any Compact Mac can be flattened for LCD installation. Milling and flame polishing the milled surface exposed in one of @maceffects clear bezels would be no biggie. But that's tangential, maybe suggest it in your thread?
 
Last edited:

Trash80toHP_Mini

NIGHT STALKER
Meanwhile I'm badly in need of a Classic II A/B for this project. I think A/B's the only component I'm missing for getting my pile of parts up and running. Definitely need it for fitment testing of this project. So if anyone has one to spare for trade or maybe money . . .
 

Franklinstein

Well-known member
Apple's "built in memory" is a by design bottleneck to expansion capability. You won't find it hamstringing any high end system I can think of offhand. Designed in limitations to "protect the high end" are everywhere to be found, but that's my take on it, others think in terms of average users who may never upgrade their systems.
All of the first-gen Power Macs, most Centris/Quadras except the 900 and 950, and nearly every PowerBook up to the WS/PDQ had soldered RAM. Many of these were at one point considered "high end."

The Classic and Classic II didn't have a ton of space to work with internally, and their power supplies were relatively weak (Apple dissuaded third-party developers of add-on cards for this reason). Unless you're also doing an upgraded analog board and/or using an external power supply, you'll probably end up overtaxing the system and at the very least it will run hotter than most components would like, especially if you start in with PDS cards and tons of RAM.

For a simple drop-in solution I'd probably recommend taking the Classic II board and giving it a mild rework to support a 32-bit bus, 72-pin RAM, and 256 grays on the internal screen (maybe mirrored in colors on an external screen, but this would require reworking the rear bucket as well (or omitting the external floppy port)). Basically it would use most of the same chips from the LCIII transplanted to a CII form factor. Not sure where you'd get the chips though.
 

max1zzz

Well-known member
I wonder if one could probably even get the LC 475 design to work in a classic chassi.
Indeed the same approach could be used with a 475 board but as @Trash80toHP_Mini says we targeted the LCIII mostly becuse I have working reverse engineered replica's. The 475 is actually a target of mine for reverse engineering but as we belive it is a 6 layer board the method I have been using (Which is basically tracing the board) won't work for it so i'll have to reverse a schematic first then redraw the board (And I have another project to practice that on first before tackling the 475)

LCIII board was developed in ____?____ which doesn't lend itself to mooshing components around. So the LCIII in SE/Plus project has been moving into KiCAD as will this project as well, if and when.
That would be Sprint Layout, it's fantastic for tracing a board but as it doesn't define a connection net it's a right pain to modify boards made in it! I'm currently using the board layout done in sprint to create a schematic in KiCad which I can then use to redraw the LCIII board in KiCad :)
 

Trash80toHP_Mini

NIGHT STALKER
Hey max, thanks for the explanation.

@Franklinstein What you've described is pretty much what we're doing here already in a nutshell:

Parts are from a Maxelled LCIII board, design is a done deal and schematic development in KiCAD is in progress. What you've suggested is an entirely new design for all practical purposes, definitely not a "mild rework?" Limited PCB real estate remains problematic.

Aux power supply hooked up to the A/B's AC input lines would be a given, not yet mentioned. ;)

All of the first-gen Power Macs, most Centris/Quadras except the 900 and 950, and nearly every PowerBook up to the WS/PDQ had soldered RAM. Many of these were at one point considered "high end."
The Quadras you're talking about weren't hamstrung by soldered RAM hogging a memory bank. They all had had provision for SIMMs installed to achieve full loadout, rendering anything on board moot, no?

No Centris was ever a high end machine, mid-range what the moniker describes.

PowerBooks don't count. ;)
 
Last edited:

Trash80toHP_Mini

NIGHT STALKER
The 475 is actually a target of mine for reverse engineering but as we belive it is a 6 layer board the method I have been using (Which is basically tracing the board) won't work for it so i'll have to reverse a schematic first then redraw the board (And I have another project to practice that on first before tackling the 475)
If I might suggest as it hasn't come up in PM. Skip right over that target and set your sights on the Quadra 630 with two SIMM slots of the PC Compatible version. Heh! ;)

edit: forgot to mention that 605/475 boards are precious. There will be a lot more battery trashed 6xx donor boards available as well as boards from PSU failed machines and mustard colored cases that can be repurposed without being overcome with guilt. :)
 
Last edited:

Franklinstein

Well-known member
True: the high-end Macs didn't have soldered RAM monopolizing any address space, and it was cumulative, which is why most of these had goofy RAM maximums (like the 6100's 8+32+32=72MB).

The Q630, however, even in double RAM slot form, was one of the compromised models: it could only use a single-bank SIMM in the second slot because the onboard RAM used the other bank. If you were going to rework that board, I'd omit the onboard RAM and send the lines to the second SIMM slot.

Anyway it looked like feature creep was making its way in so my previous suggestion was to keep the spirit of the Classic II's logic board: connector-compatible, no PDS, no extra power, no case mods. The Color Classic and CC II share the same logic board space, which is roughly the same size as that of the Classic II, and since comparing these is pretty close to comparing the capabilities of the Classic II and LC III, I didn't figure it would be a big deal to add some more lines between the CPU and the memory/video controller chip while keeping it in the same general footprint as the original Classic II board. Also, if you're going through the trouble of a full redesign, drop the ROM/FPU expansion slot and have an FPU socket directly on the logic board instead. Omit the soldered RAM and trade the 30-pin SIMMs for two 72-pin SIMMs (though they'll probably have to be at a steep angle to fit properly). Use a ROM SIMM instead of the four big masked ROMs on the logic board. Should have enough space.
 

Trash80toHP_Mini

NIGHT STALKER
True: the high-end Macs didn't have soldered RAM monopolizing any address space, and it was cumulative, which is why most of these had goofy RAM maximums (like the 6100's 8+32+32=72MB).
Yep, Apple marketing won out over engineering, ostensibly protecting sales at the high end 840AV and some others shipped with 4MB, but topped out at a round 128MB? Was stock memory implemented on the board and then ignored or in SIMMs?

The Q630, however, even in double RAM slot form, was one of the compromised models: it could only use a single-bank SIMM in the second slot because the onboard RAM used the other bank. If you were going to rework that board, I'd omit the onboard RAM and send the lines to the second SIMM slot.
The reproduction board that @max1zzz pulled off so nicely was one (stupendous!) thing. But you can rest assured that none of the projects we've been discussing are to be hamstrung with Apple's piddling amounts of stock memory cluttering up the board. Every LCIII takeoff will be all SIMM designs as would the 630 board I suggested. That one's a doozy with its rudimentary IDE support and all kinds of toys in a box or slimmed down to fit the 128K/512K, no options offered.

If I ever found my Q630 board, it'd already have had one of my collection of 72pin SIMM expanders permanently installed with bodge wires connected to every available CAS/RAS line on the pads a/o Controller. The Q605 will require a custom SIMM expander and requisite bodge wires for same.

One day perchance. :rolleyes:

Every bit of memory will be on that Riser if this project happens, all in SIMMs, the pads for ICs are on wasted real estate. The concept there is to provide a sandbox for building experimental cards of all sorts. If you can believe it, my several pages of conversation with max started out under the PM topic: Nubus in LCIII ;)

Anyway it looked like feature creep was making its way in so my previous suggestion was to keep the spirit of the Classic II's logic board: connector-compatible, no PDS, no extra power, no case mods.
Classics were about NOTHING but tat $999 price point. Pulling that off using as few on hand component designs as possible, using the cheapest CPU available and cutting ever identified corner would be the spirit of the Classic. The Classic_II was pretty much the same kind of rehash.
 

Trash80toHP_Mini

NIGHT STALKER
Nope, @max1zzz said it was one of his targets and that he hoped to get to it . . .

. . . I'll do my best to sidetrack him onto doing a revved up Quadra 630 that can go into one of my 605 cases. The only thing missing is an upgraded VRAM/Video Subsystem. IDE on board rocks! It will also fit in a Compact case and drive grayscale :p
 

Trash80toHP_Mini

NIGHT STALKER
Anyway it looked like feature creep was making its way in so my previous suggestion was to keep the spirit of the Classic II's logic board: connector-compatible, no PDS, no extra power, no case mods.
I'm beginning to come around to that same viewpoint, but not ready to succomb to temptation as yet. ;)

I hope this will condense/clarify current considerations:

Apple put the the Classic in a tightly fitted straightjacket with the mezzanine level logic board mount strategy. Addressing that issue by dropping the board to ground level requires an additional ports PCB and more complicated installation process of the resulting kluge. Not good.

PDS (and probably VRAM?) on the memory subsystem riser is looking like it may need to be dialed back for KISS principle adherence. What started out as a way to condense the logic board footprint of built in RAM, DIP ROM and VRAM(?) slots would require the equivalent of widening the LCIII's ROM SIMM to that of a 72pin SIMM.

ROM and main memory can easily co-exist on a slightly modified version of the (active component/buffered) 72pin SIMM expander I have on hand as a reference design.

But VRAM is another question entirely, gut tells me that's a brick wall? Bringing PDS control lines (and VRAM lines?) up that narrow alleyway can't be done. So unless I come up with a workable interface, anything more complex than ROM slot/SIMM expansion is a no go. PCIe x16 slot connector's looking like a great prospect for getting everything on there without going Rube Goldberg on the project, but suitability needs to be verified.

No case modification is already in the specification.

There's no way around the requirement for additional power of any Classic board replacement worth doing that I can imagine.

I've already solved that power problem I think? Apple's ridiculous mezzanine level logic board makes makes that a slam dunk. The cubic underneath the Logic board seems ready made for adapting the PSU board from just about any LCD Display or the likes of a DVD player headed to recycling due to panel or mechanical failure.

Sourcing such a generic PSU board currently available may not be recycling correct, but would be KISS compliant. PSU board needs to be less than 170 x 120 millimeters for it to bolt up underneath the new logic board for the assembly slide into the chassis rails. I'd think anything in production will be 120/240 switchable?

There's no way to get around soldering a fused (and current limited?) AC connection cable from PSU to the A/B. Specifying such is well above my pay grade. For anyone up to building one of these boards, soldering that connection will be rudimentary by comparison. Soldering the AC cable extension will be well within the skill set of most folks interested in this lunacy and can be done and tested by a local friend for the rest of us.

Thoughts?
 
Last edited:

Trash80toHP_Mini

NIGHT STALKER
164 pin PCIe x16 interface is looking very interesting for Classic III. VRAM and PDS can safely stay in the spec. However I'll stick with the 240 pin DDR2 Memory Module interface for a next level project coming up. So all's good so far in HackLabNC. :)
 

Trash80toHP_Mini

NIGHT STALKER
Here's a visual on the generic power board approach:

42inchTV-PSU-00.JPG

This one is too big and definitely too tall, but I'd harvested it from an old school 42" LCD TV with the analog/VGA features. I snagged it from beside the recycling dumpster of my apartment complex. LCD was toast, but very pretty pattern and its boxed entrails were right where I thought they were! Fused AC cord connector and cable lower left. That's what needs to be lopped off and soldered to the AC connector joints on the A/B. DC voltages are on connector upper right. Had to lop it off because the logic board side is soldered.

Putting the LC series type power connector on the bottom of the logic board's a mess waiting to happen. But point flat Molex deal at the slanty side of the fan's ductwork for that lopped off power connector cable loop and we're good to go. AC cable's easily snaked around there as well. Connector for it would be plugged in while the logic board/PSU assembly is slid into the chassis.

Board's good and will work just fine for this knucledraggin' hacker's playtime. Voltages are documented right on the silk screen layer. Metal mounting rails are a big plus. Output is crazy overkill for an LCIII board. Can't imagine we won't be able to source a stock item, smaller PCB, low profile version with power to spare if this craziness gets anywhere.
 
Last edited:

apm

Well-known member
Nice project. Yes it should be possible to mod the Classic II A/B to get higher resolutions, and then use one of the Xceed clone CRT neck boards for greyscale. I've made a custom A/B in SE/30 form factor incorporating the Classic II flyback, which I built probably a year ago but has been sitting in the closet waiting for some proper time to look at it. Of course here the situation is simpler still, since you can just use the existing A/B with a few modifications.

You can buy small DC step-up converters that could supply the horizontal sweep circuitry to eliminate the need for the benchtop supply (which was more for my testing than for any notion of long-term deployment).
 

mogs

Active member
The A/B can be considered as three separate systems (PSU + audio + video).

I've managed to lobotomize the PSU components and hack in a Pico ATX PSU.

Was working nicely till the battery rot finally took out the logic board.

Anyway a similar approach might work here?
 

mogs

Active member
So putting an ATX connector + audio amp circuitry on to the replacement logic board could mean the AB can be stripped right back to just a (modified) video circuit (+DC-DC boost to 31V for CRT) run from a molex.
Then an off the shelf (Pico or SFF) ATX supply can be used either internally or externally.
 
Last edited:

Trash80toHP_Mini

NIGHT STALKER
Welcome back to the fray @apm ;)

Hiya @mogs welcome aboard, though I am a little late on that count. Nice project, can't believe I missed it, but that was a crazy year for all. The AliE links are still good too, wow.

We've got AC heading into the A/B in the usual manner and nowhere for external DC in to look like it belongs there? Lump-on-a-rope always bothers me, especially when Apple builds something pretty to sit on display like the Cube and hangs a big DC converter off the edge on a rope. NOT elegant. :p

I've been thinking along the lines illustrated above rather than the usual FlexATX kinda thing. Without the need to power the standard logic board the A/B needs but power itself which would work well enough I think? Plenty of cooling appears to be swirling around aimlessly by that ducted fan setup. Enough wanders out the vent for cooling from overpressure, but some feedback goes back down the chassis grating at the back into the mezzanine level logic board and the dungeon below it for that open face sandwich kinda PSU I think. Powering FDD, LCIII board, somethingorother-to-SD and SCSI-to-whatever should be fine if we can identify a suitable candidate?

Target's a modified version of the @max1zzz (done deal) LCIII recreation, so everything sound related is on board if we do a hybrid A/B design. He's in the process of reversing his layout back into a schematic in KiCAD for rework ATM.

Have either of you worked out a schematic for the Classic II A/B design?

That SE/30 form factor A/B sounds like the thing if we need to go the conventional PSU approach, scads of room for it with that design.
 
Last edited:

mogs

Active member
@Trash80toHP_Mini Thanks, it was fun to get to that point, too bad I've run out of working classic 1,2 logic boards. Once the house is built I'll hopefully find time to play with these again. Been watching the logic board recreation threads with interest.

I do like the SE/30 style AB form factor idea. Either as a new board or retro-hack.

The Bomarc schematics are quite readable, and only a single copper layer, so pretty accessible.
 
Top