Switching processors between 520 & 540c

[pcamen]

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?

 

[Bolle]

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.

 

[pcamen]

Yea, as soon as I find a good guide to opening those things up.  I've tried on a couple to remove the front plastic to disassemble them but always end up breaking something. 

 

[pcamen]

Looks pretty original.  Bummer.  I was hoping to get a full 68040 on some of my 540c's. 

 

[pcamen]

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

 

[Paralel]

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

 

[pcamen]

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. 

 

[Paralel]

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?

 

[Macdrone]

Ya looks like system profiler lied.  It says LC right on the chip.

 

[pcamen]

Ok, I'm going nuts.  I could have sworn that (a) what I saw was a full 040 and (b) I took a picture of it and posted that here.  But I was wrong, both were LC varieties.  Darn. 

 

[Byrd]

Just a quirk with Apple System Profiler - use Norton System Info for better info

 

[Franklinstein]

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). 

 

[Paralel]

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

 

[ArmorAlley]

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.

 

[CC_333]

Please forgive my ignorance, but how is a full '040 in a 540c better than an LC040, give that both operate at 33 MHz?

c

 

[Cory5412]

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.

 

[pcamen]

Yup, just to say I did, that fits. 

 

[CC_333]

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

 

[pcamen]

How about both?  A full 68040 overclocked? 

I agree, it's academic.  But for some reason there is something that keeps nagging at me that says ... it could be just a little better.