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Switching processors between 520 & 540c


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I've got two PowerBooks, a 520 and 540c, that I acquired in a large lot last year.  The 540c, like most, has an LC040.  But lo and behold, I found that the 520 has a full 58040.  However, the 540c is at 33 MHz and the 520 at 25MHz.

 

So my question is, would it likely work to pull the full 040 from the 520 and use it in the 540c at the full 33MHz?  I'm not sure if the crystal is on the processor daughter board or on the motherboard.

 

Anyone know?

 

 

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IMG_5753.jpeg

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Wow, that's odd.

The crystal which sets the whole sytem speed is on the CPU card, so swapping the cards will give you a 25MHz 540c.

You will have to put on another crystal and see if your CPU works when overclocked to 33MHz.

Can you take pictures of the full 68040 card in question? Curious to see if it was reworked or if it came that way.

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51 minutes ago, pcamen said:

I found another one in my stack of these units - a 520 - that also has a full 68040 at the slower speed.

Can you post pics of the CPU Daughterboard?

 

Apple never made a full 68040 @ 25Mhz, so it is either a replacement someone did of the main CPU, or its a 3rd party upgrade that no one knows about.

 

However, if you're basing this purely on the Apple System Profiler in MacOS 8.0 running on a 520, and not actually looking at the CPU daughterboard, I can say, with almost absolute certainty that it will turn out not to be a full 68040. The MacOS 8.0 Apple System Profiler doesn't bother to distinguish between a 68040 and a 68LC040 in its reporting, it will say 68040 for either type. It's just laziness on behalf of the ASP in MacOS 8.0

Edited by Paralel
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3 hours ago, pcamen said:

Ok, that last one was a red herring.  I must have misread the system info, as the processor is an LC variety.  So just the one above is the confirmed full 68040 @ 25 MHz now. 

You mean the one in the pic? That's an LC, not a full 040. Have you put up a pic of the full 040?

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The only full '040 PowerBook from the factory was the 550c. It's possible someone could one day find a DVT 520 or 540 that has a full 040, or one that got a 550c's card transplanted into it, but none were sold by Apple in that configuration.

 

Unfortunately it's very difficult to find a QFP 68040 that isn't either NOS or pulled from an existing system; it appears Motorola/Freescale discontinued it some time ago in favor of the 68040V, which is basically a low-voltage capable LC chip (so it lacks an FPU). 

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On 3/21/2019 at 3:30 AM, Paralel said:

That's what I did. I got a 550c CPU Daughtercard from Japan and put it in my 540c to have a full 68040 @ 33 MHz

I'm hoping to do this some day. I bought a 33MHz 68040FE chip once when Techknight recommended them and I hope to to be able to transplant it onto my 540c daughterboard. If I remember correctly, Bolle commented once that it could be done with a hot-air station.

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In any given system, a full '040 would be beneficial purely in situations where you want to run floating point math of some kind. Typically, math/science, development, some graphics applications, or if you are running a system that supports it, such as a 650 or 800, it makes running Linux/BSD a little easier.

 

To my knowledge, because most games at the time would've been targeting LC/Performa series computers, close to zero of the day's games get a boost out of a physical floating point unit, and any that do should still be playable without it, again, because the target would've been 030 and LC040 Performa and LC computers, often at lower clock speeds.

 

If you were maxing out a computer for fun, and weren't otherwise doing any of the technical/pro/graphics work mentioned above, you might put in a full 040 just to say you did it.

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I see.

 

In that case, my logic tells me that a faster LC040 running at, say, 40 MHz, is more beneficial than a full 040 running at the stock 33 MHz or 25 MHz, yes?

 

At this point, I'm not sure if I want to do it because I can; I want an upgrade to be useful for something (upgrading to a faster CPU, to me, is a lot more useful than a variant of the same CPU running at the same speed, but with extra features that most software probably won't care about.

 

c

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8 minutes ago, pcamen said:

How about both?  A full 68040 overclocked?

True point. The thing is, though, that to me knowledge, LC040s of any speed are easier, and thus cheaper, to come by these days than full 040s, particularly in the form factor needed for the 540's CPU card.

 

c

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2 hours ago, CC_333 said:

In that case, my logic tells me that a faster LC040 running at, say, 40 MHz, is more beneficial than a full 040 running at the stock 33 MHz or 25 MHz, yes?

It depends on what you're doing.

 

Truth be told, I have yet to see significant evidence that most people are doing high end work with their vintage Macs, so for most people, a 40MHz 'LC040 would be more beneficial than a 33MHz Full040.

 

1 hour ago, pcamen said:

How about both?  A full 68040 overclocked?

The only real need for this is typically bragging rights. The handful of people I know doing work on their upgraded or overclocked '040s don't post about it for the sake of bragging that they have, of all things, an FPU, or that they've managed an overclock.

 

1 hour ago, CC_333 said:

particularly in the form factor needed for the 540's CPU card.

This is the real kicker for this particular thread - it's not like we're talking about an 800/850/950 here.

 

The biggest gotcha, of course, is that of course the PowerBook 550 did have a full 040, and I don't know if there are any heat differences between the full and "LC" versions of the 040. If not, then it doesn't really matter, and any given form factor either "can" or "can't" cool an 040 at a given speed, regardless of what type it is. (but, again, that depends.)

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On 3/22/2019 at 3:32 PM, pcamen said:

Yup, just to say I did, that fits. 

That's the ethos I work from.

 

As far as trying to install a faster LC040 in a 540. You'd need to implement some kind of cooling solutions, such as a low profile heatsink, similar to what is seen on some of the PPC upgrade cards for the 540, because the full 040 @ 33 MHz is known to cause the 540/550 to exceed its thermal budged and lock up on hot days, because it is borderline with the sad cooling solution in the 540/550. I doubt it would tolerate an LC040 at a higher speed very well.

 

Also, I don't think they ever made an LC040 @ 40 Mhz QFP. I've only ever seen a full 68040 in PGA format. 

 

Edit: From looking through NXP's site, they did indeed make a 68040 @ 40 MHz QFP, but only in the full 68040, no LC, so no doubt it would indeed exceed the thermal budget of the 540. You'd need a cooling solution for sure.

Edited by Paralel
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I found the reason why there were never any attempts to make 68040 @ 40 Mhz QFP upgrade for the 500 series at that time, the part didn't exist. From what I can tell reading NXP erratum, the QFP format for the 40 MHz part didn't exist until the 21st century at Freescale when they moved the 68040 (at that time meant for embedded applications) to a newer fab process. 

 

Technically, it should be pretty simple to implement this type of upgrade now. Just make sure you have the right crystal, and that should be all you need.

 

I'll leave this to someone else though, from what I can tell doing a quick search, people are asking ~$380 for a MC68040FE40A. Too rich for my blood.

Edited by Paralel
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Even with a heatsink, the 040 on my DayStsr even idle gets HOT. Granted it's OCd from 33 to 40 via oscillator, but even with the passive arrangement it's toasty. I might check it with an IR thermometer out of curiosity.

 

Definitely got hotter than my Q610 ever did.

 

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