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Mac LC III 16mhz?

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I just picked up a macintosh LC III and it works ok, although the capacitors are failing.

 

What i noticed, is everwhere i read the macintosh LCIII has a 25mhz 030. Mine has the exact logic board an LCIII would have, but it has a 16mhz 030.

 

Any ideas why?

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I have no idea...no LCIII ever shipped with anything less than a 25 Mhz 68030. Are you sure that its actually an LCIII board and not an LCII board? If its an LCIII board, it will have an FPU socket and one RAM slot for a 72 pin SIMM, as well as an enhanced LC PDS slot. If its an LCII board, it will have solder pads for an FPU socket, but no actual socket, and two RAM slots for 30 pin SIMMs, and a standard LC PDS slot.

 

Unless by some chance its a prototype, this is the only way I can figure as to how an LCIII would end up with a 16 Mhz '030, since all the boards between the LCII, LCIII and LC475 are completely interchangable.

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Possibilities:

 

1. God sent you this rarity so that you could sell it for lots of money on eBay (genuinely a one-off) and give the proceeds to the poor.

2. What LCGuy said - it's not an LCIII.

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I did a youtube video on this machine. best way for me is to get pictures of it.

 

Anyway, yes its an LCIII as it has 1 ram slot, and an FPU socket.

Edited by Guest

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Thats really quite strange, thats definitely an LCIII board, but no LCIII was ever sold with anything less than a 25 Mhz 68030, and yes, thats definitely a 16 Mhz '030, otherwise it'd have a MC68030FE25B.

 

I dunno, the only thing I can think of is that Apple did a limited production run of 16 Mhz 68030s in one country because it would have cost too much to sell 25 Mhz LCIIIs there....thats really the only thing I can think of. Apart from the fact that it has the 16 Mhz chip, the board certainly looks identical to a regular production board.

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Those solder pads are in all production model LCIIIs, no LCIII that I've seen ever had a switch there, just the solder pads.

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its definately strange. thats the first thing i noticed when i opened it up. seen the 16mhz CPU, and was like, what the heck?

 

Me hurrying up and sell it for one fluke? or think it just became extremely valuable for one fluke? not a chance. im not here for the selling money game. im here to play with these things. ive had LCs when i was a kid and i wanted to get another one to monkey around with.

 

also there isnt any telltale signs that it came from another country either, as it looks like a plain english install. the volume creation date is 1999

 

it also might be a 16mhz IC overclocked to 25mhz stock osc speed. reason why i think this is becuase the chip gets extremely hot. hotter than comfortable. but it runs ok without a heatsink. Any kind of program out there like apple system profiler would tell me what its running at?

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Well, I'd say either look for a normal LCIII motherboard or seek someone out with a broken LCIII board with a working CPU and get the chips swapped. It really shouldn't matter since an normal 16MHz '030 in a LCIII should outperform one in an LCII since the LCII has that 32-bit? processor on a 16-bit motherboard (address/data bus?) where as the LCIII should have a 32-bit motherboard (address/data bus?).

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Further to this one:

 

In a box of components that I am putting on eBay, I came across a small AIO logic board with a 68030 marked 16MHz, and assumed it was a Color Classic. I took it out to pop in a Color Classic for testing, got my two 30-pin SIMMs out, and proceeding to put them in ... discovered that it took a 72-pin SIMM. It was from an LC5xx machine.

 

For obvious reasons, I fired it up, and discovered that it runs at 25MHz. It is not an exact match for my other LC520 logic board (presently being auctioned, and which is marked as having a 25MHz chip), but it runs at the faster speed and works perfectly in the Color Classic (which thinks it's a Color Classic II in the diagnostics software used to test the components, despite its running at 25 rather than 33 MHz). I confirmed the speed with Gauge Pro, Apple Personal Diagnistics and MacCheck.

 

Thinking this was rather interesting, I then compared the chip markings on the two logic boards tested, and discovered this:

 

Color Classic @ 16MHz:

MC 68030FE16B

04D66C

QEWD9325

MALAYSIA

 

LC5xx @ 25MHz:

MC68030FE16B

04D66C

QEWV9250

MALAYSIA

 

Assuming the last line is a date code or something, they're surely the same.

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Yea mine ran at 25mhz as well. overclocked 16mhz probably for cost reasons.

 

Anyway, reason i said "ran" as in past-tence as when i put it to work as a "real" every day use machine, it has since died and in need of a cap replacement so one of these days i need to get around to doing that.

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Well, 68030s don't run hot, and it does seem that some of the 030 machines were deliberately underclocked so as not to compete with the higher end models, like the IIsi over against the IIci, the processor in the IIsi being perfectly capable of running at IIci speeds, even though the model was clocked slower.

 

Use of the chip with those markings in the faster machine could have been just a cost-saving measure, after there was a batch of 68030s produced that proved to be better than expected or some such, or maybe the factory simply put the wrong stamp on the chip.

 

It is a little odd, however, that we two have discovered the same thing simultaneously in two different 25MHz machines of the period. (Interestingly, the LC520 is spoken of as architecturally very similar to the LCIII, much like the LC475 and 575, so maybe it occurs in these two models only.) Googling turns up nothing on it for me beyond this thread.

 

I can say that the board with the chip marked 16MHz has the same components as the other LC520 board currently in my possession, but some components have been moved around very slightly. So presumably it is an early or late revision that I have.

 

I'll try to take some pics for the Flickr group before I sell the boards.

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No, it's soldered.

 

Searching for the l.b. part number today, I stumbled on this over on Applefritter, towards the bottom. Evidently it's not so rare after all to find 68030s on Apple logic boards marked as slower than they really run.

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I acquired a second LC III yesterday, and ran across this thread. I took my earlier example out and it has the 16 MHz chip too. The one I got yesterday has the 25 MHz. The one with the 16 indicates it was assembled in Malaysia and the 25 assembled in USA. Both boards marked as "Singapore Rev" and have identical components except they boards themselves are slightly different colors.

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