Speeding up a Color Classic - Without mystic or Takky

[PhidoMac]

I have a colour classic. I am spending some time restoring it, recapping it and the analog board, VGA mod, etc. I know at the end of it, I will have a very slow Mac.
But I have been having deep thoughts about how to make it faster.

The days of finding lazy 575 or 550's for cheap are long gone, and people now know these are worth something. While in big markets like the US it is possible to find them, shipping etc adds significantly to the cost, and fundamentally, you are changing the board. At some point its no longer a color classic, but a home for another machines board, which by the time you do the takky mod, you might as well put a whole new machine in there like a Rasberry Pi as you are just using the CRT from the original computer and molesting the insides in a non reversable way.

So I wonder, if we are keeping the modifications to the original motherboard what options are there:

• It is generally listed as these Macs are not overclockable, yet the LCII they are based off are. Looking at the mobo its got a 31.3344Mhz clock crystal that I assume is clock divided to 15.6 Mhz. Perhaps a crystal change or a clock generator would be useful here. 16Mhz was quite slow for the vintage of this computer and the RAM and VRAM should be able to handle a bit of clocking looking as it is as 70ns DRAM and 80ns VRAM . I would imagine a 40Mhz, 50 or 66Mhz crystal could be at least tried. I believe the graphics portion is downclocked from the base clock on the LCII there is a seperate clock generator, and it has been able to be overclocked seperately.
• Now I know that Mac Effect has a clone of the original MicroMac Thunder 68030 32Mhz accelerator. A seemingly simple and highly compatible accelerator. After I finish restoring my colour classic, I am considering buying it, perhaps after experiments in overclocking. Has anyone run one of these boards in an overclocked LC/LCII/Color classic? If shooting for something like 20Mhz clock, then I assume these would clock double that AFAIK they don't seem to have a crystal soldered onto them? A 40Mhz 68030 would seem possible with a 50Mhz being perhaps worthy of a try with a heatsink attached? Are these CPU's socketed?

 

[Phipli]

Straight up your issue with overclocking vs the LC II is there is only a single clock on the ColorClassic. Perhaps you could copy the circuit from the LC II, but you'd be working things out yourself, I haven't heard of people doing it before.

There are a few very timing sensitive things on macs, like video, serial and the floppy drive, if you change the clock more than a small number of single digit percent, they'll stop working properly.

A PDS upgrade card is probably your best bet.

 

[Byrd]

At the end of the day you’re not going to get much out of overclocking the stock board, in terms of performance and potential. Keep up the look for a PDS accelerator or LC520 board is a straight swap if you can find. Japanese auctions might net you some good results.

 

[pizzigri]

I had been offered a 520 board here at a reasonable price, I think it was Slomacuser, when I was looking for a 575 board.
I do not see it too much of a heresy to place a 575 board in a CC, since “mystic” does refer to a cancelled CCIII.... how credible is this claim may be debatable however it’s a lot less invasive than a takky - couldn’t agree more.

 

[mg.man]

if we are keeping the modifications to the original motherboard what options are there:

Also:

https://68kmla.org/bb/index.php?threads/fs-interware-booster-30-l33f-clones-lc-ii-32mhz-accelerator.41222/post-485150

 

[PhidoMac]

A PDS upgrade card is probably your best bet.

Probably. But I am not after easy. Or even cost effective. I guess I am after new ways and different ideas.

There are a few very timing sensitive things on macs, like video, serial and the floppy drive, if you change the clock more than a small number of single digit percent, they'll stop working properly.

Serial and floppy is less important these days. With an adjustable clock generator like the spicey clock, it might be fairly straight forward to clock it up, and 16Mhz is very, very slow for 1992-4, most of these peripherals can operate at 20 or 25Mhz bus. It is when people are pushing 33 or 40Mhz in 040's or 20-25Mhz on 68000's or 68020's on 1980's motherboards there are issues. Changing clock crystals is fairly easy, it can be done literally in minutes.

I had been offered a 520 board here at a reasonable price, I think it was Slomacuser, when I was looking for a 575 board.
I do not see it too much of a heresy to place a 575 board in a CC, since “mystic” does refer to a cancelled CCIII.... how credible is this claim may be debatable however it’s a lot less invasive than a takky - couldn’t agree more.

Oh, look, my personal preferences I wouldn't want on anyone else, and yeh mystic and Color Classic II are a thing. But sticking a 575 or even a 520 board is pretty easy if becoming a rarer commodity. Also people seem to trash the Performa/LC these come out of, removing macs from circulation.

Then it raises the question, what the hell happens to all these original Color classic and LCII motherboards! Are people throwing them in the bin? Surely a small kick in performance would help resale!

https://68kmla.org/bb/index.php?threads/fs-interware-booster-30-l33f-clones-lc-ii-32mhz-accelerator.41222/post-485150

Wasn't aware.. I am interested in the bare boards. Something like that may satisfy my tinkering needs.

The issue with these accelerators is they are still fed by a paltry 16Mhz 16bit bus. If we could get it to 20 or 25Mhz, It would be a 25%-56% improvement in memory/graphics/ALU.. If you could get the 16Mhz bus to 20Mhz, a measly 4mHz gain would still result in a 25% faster bus, which could then feed a clock doubled CPU at 40Mhz.

AFAIK these clock doubling boards only clock up some of the time, when the bus allows it. So getting a 40Mhz or 50Mhz overclock may be much more achievable than on a application where its always 40 or 50Mhz. Which is why it seems people are having success with 16Mhz CPU's clocking at 32 Mhz on these boards.

If we could get 25Mhz on the bus and 50 Mhz on the CPU, that would be a 56% memory/video/bus/clock and 312% ALU processing. improvement.

 

[Unknown_K]

A Sonnet Pesto Plus is what I would recommend if you have the cash. There should be 550 and 575 motherboards out there from systems shipped and destroyed in the process.

 

[just.in.time]

A 520 logic board can be bumped from 25mhz to 33mhz (which I believe is what the 550 board runs at) by moving a resister on the bottom of the board.

Also has the benefit of not being limited to 10MB of RAM like the stock CC board.

 

[pizzigri]

I could agree with you on this matter, however unlike the Mystic that admittedly was cancelled, the Color Classic II is not “a thing” it’s an actual model, that if you’re lucky enough, you can actually buy. Plus, to answer your other question, the plastic quality of the whole 520/550/575 line for reasons unknown is WAY worse than the CC line. some of these actually disintegrate on their own even just sitting on a desk. it’s like having an entire computer made of paper thin blown glass that cannot support its own weight. So I can tell you, today no one would buy or intentionally destroy a 575 just to harvest the LB, not when a complete, functional and healthy unit is valued way more than a stock CC.
but in the even recent past, when the 5xx were plentiful- i.e. sold as scrap from schools - many have removed the LBs still circulating today.

 

[defor]

personally from the prices I've seen, while the price on a 550/57x board might be high, the price isn't that far off from the accelerators designed for the CC/LCII/etc.
The added benefit at the end of the day if you're seriously looking to upgrade is that you get to keep your PDS slot, which most accelerators end up using.
SCSI/localtalk to etherent options (if you want more modern networking) aren't ideal, and bring another set of costs...
I've only ever seen one option for driving displays over scsi and I can't for the life of me remember what it was called, but again, it wasn't great... etc.

The CC, along with most AIO macs, is a nice started bundle, but in the modern day, i find that it's really easy to start needing some expansion or connection tot he outside world, and PDS is kinda invaluable on this front.

 

[pizzigri]

@defor that is absolutely right, plus the 575 board offers another invaluable feature: a Comm Slot for an ethernet card leaving the PDS slot free for whatever other upgrade you may fancy. In this scenario, it makes sense to upgrade the HD to a SCSI to SD for power budgeting

 

[defor]

sorry i forgot to mention the CS1 slot - a great point as well.
I'm not sure changing from scsi to SD for the drive is necessary, as I've always run cc's even back in the late 90's with 550/570 boards with no issue.
A simply analog board recap should be all that's necessary.
I'm more a fan of moving to SD adapters (take your pick on brand, I'm not picky) because of the long-term durability of a SD card sitting idle compared to an old seized rotary drive.

 

[pizzigri]

I found that an original Apple CS1 card fits perfectly inside a CC frame without any mod except for the plastic “rib” holding the HD power cable and removing the Ethernet card shield.

 

[pizzigri]

However, To the OP: I understand that a Mystic is in a way tampering with the originality of the machine - need for 640 mod - I would then suggest to source either a 520 or a 550 logic board because It simply fits without any modification, down to using the original rear panel.
This way, the Color classic earns a considerable power bump, with a 33mhz 030 CPU/6882 FPU, up to 32 MB of RAM and a full 32bit data path - and better video too.
And if I want to have the experience of using the stock color classic, all I need to do is swap the 550 logic board with the original - not much different that popping out a PDS upgrade board from the LB - and done!
another advantage, that disappears with a Takky and somewhat also with a Mystic ( but is perfectly reversible in the latter) is that collector value and originality of the machine is completely preserved with the 620/550 upgrade.

 

[Phipli]

most of these peripherals can operate at 20 or 25Mhz bus

It isn't so much what the chips can clock at individually, the ROM code and logic board glu are designed to operate at a certain speed and with the least capable chip on the board. These things just... don't overclock.

All macs that are overclockable either have multiple clock sources, or some kind of multiple output clock divider/multiplier that can be set with resistors.

This computer is unlikely to boot even with a 5% faster clock. But, like you say, it's easy to replace the clock to see. In fact, if you use the output enable pin, you can switch off the built in clock and inject your own without even removing the stock clock. Might be good for a quick test

 

[DrGonzo]

I had the same thought as the OP in keeping my CC original but wanting a speed bump. That's one of the reasons I'm building a few of these for my CC and my LCs:

GitHub - TheRealBolle/Tokamac-LC: 25MHz 040 accelerator for the Macintosh LC/LCII/CC

25MHz 040 accelerator for the Macintosh LC/LCII/CC - TheRealBolle/Tokamac-LC

github.com

I'm hoping it provides near 'mystic' performance at a reasonable cost, while keeping the CC as close to original as possible. We shall see...

Regards,
~Dr. G

 

[PhidoMac]

I'm hoping it provides near 'mystic' performance at a reasonable cost, while keeping the CC as close to original as possible. We shall see...

Well with an accelerator they are easy to restore it back to original condition. Part of these old machines is the slowness. Sometimes its useful to demonstrate that, say when you are setting up two machines next to each other for display. An accelerator can easily be removed and slowness demonstrated, particularly on LC's and CC.

 

[Unknown_K]

Cloning the Presto Plus (extra RAM + Ethernet along with the 040) would be something people would buy.

 

[pizzigri]

Cloning the Presto Plus (extra RAM + Ethernet along with the 040) would be something people would buy.

This, but it would NOT be cheap. On a level of a 575 board if not more, I reckon.
still, swapping a logic board in a CC is easier that removing a PDS accelerator - in both cases the board has to be extracted from the machine.....

 

[Unknown_K]

I have no idea what adding RAM and ethernet would cost on low run boards, but cloning the bare Presto (which is a renamed Tokamac part if the above is true) can't be cheap either.