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Source for last generation L88M m68040?


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I started an archiving project using a Mac Quadra 610 here:

https://68kmla.org/forums/index.php?/topic/25007-starting-archiving-project-using-quadra-610/

 

However, the 50 MHz NewerTech Quadra Overdrive proved to be not all that stable. The rest of the machine is 100% stable running at 25 MHz without the Quadra Overdrive, and I'd like to fix that.

 

Does anyone know of a source or sources of the last mask .57 micron L88M Freescale / Motorola chips, aside from the $50 ones on eBay?

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Hi John,

 

It's funny that you mention this. I have a Quadra Overdrive in my Performa 475 and it does behave erratically every now and then. It also blocks the network card. I installed AppleShare 4.0 on the P475 and the two don't play nicely together.

 

Thanks for the confirmation.

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If the cpu is removable on the accelerator card, then why not just pop it into the quadra and swap the onboard oscillator. It won't be as fast but at least it's faster than what you got...

 

"Quadra 610

The 25 MHz Quadra 610 replaced the 20 MHz Centris 610 and uses the full 68040 CPU, not the FPU-free 68LC040 version. The oscillator runs at 12.5 MHz and the CPU at twice that internally, 25 MHz. Using a 14.7456 to 15 MHz oscillator will boost speed to 29.5 to 30 MHz while allowing the serial ports to continue to function properly.

If you don’t need to use the Mac’s serial ports, you can over clock the 610 to 37 MHz with an 18.5 MHz oscillator. You can drive a Quadra 610 with DOS card to 34.9 MHz using a 16.96 MHz oscillator."

 

- From Low end mac

Edited by 360alaska
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techknight:

 

The Quadra Overdrive doesn't change the number of wait states at all. It runs the processor at 50 MHz when the bus is relinquished by the motherboard. Everything else runs at the same, standard 25 MHz.

 

360alaska:

 

I could do that, but I'd rather get a cool, even more overclockable m68040 and run it at 50 MHz and keep the rest of the system at the standard speed for best stability. This system has had uptimes with heavy usage of many months, and I want to get back to that level of stability.

Edited by johnklos
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techknight:

 

The Quadra Overdrive doesn't change the number of wait states at all. It runs the processor at 50 MHz when the bus is relinquished by the motherboard. Everything else runs at the same, standard 25 MHz.

 

 

And thats exactly what I meant. it has to insert wait states for the bus to catch up. some peripherals dont like excessive wait states. And you cant relinquish the bus unless there is RAM, and ROM, and CACHE onboard the accelerator. Then you need a DMA interface in order for that to even think about relinquishing a bus. 

Edited by techknight
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techknight:

 

It's much, much simpler than that. Whenever the m68040 is talking to the motherboard, it is running at 25 MHz. Whenever it isn't, it's running at 50 MHz. This is why purely synthetic benchmarks such as dhrystone show 50 MHz speed - the whole main loop of the benchmark fits in the m68040's caches, so 99% of the time the benchmark is running, it's running at 50 MHz. There are no wait states - just slow states ;)

 

rsolberg:

 

I bought one a while back, but when I installed it, I immediately knew it was a counterfeit because it was an LC040. I got my money back, but I'll definitely check any I get in the future. 

 

Aside from seeing how hot the chip gets, I don't know if there's a way to verify that it's a late mask - errata all appear to have been fixed in the E71M and E42K masks. Hmmm...

 

Also, I didn't go with that seller because of the ridiculous shipping price, although I was going to make an offer, but instead I got mine for $55 USD shipped.

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http://www.ebay.com/itm/MC68040RC40A-Manu-MOT-FREESCAL-Package-PGA-32BIT-W-CACHE-MMU-FPU-/201024477214

 

40MHz version.... but it's from China.  Could be legit, old stock.  Could be counterfeit.  Couldn't tell ya.

 

That's the E42K mask, which is .65 micron - you can see the mask printed in the corner of the chip in the photo. The E42K mask is better than the original masks which came in Macs, but it's not as cool as the L88M mask (.57 micron), which also has the die mounted differently to better dissipate heat.

Edited by johnklos
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I was watching the 40MHz ones from China, but passed due to the earlier mask. If you're interested in the ones I linked above, ask the seller for a shipping quote. The calculator on that listing seems out of whack. I ended up paying about $10 for shipping, albeit within Canada. The unit I received is definitely as marked- it runs markely cooler than the XC68LC040 it replaced and is identified as a MC68040 in software, FPU benchmarks run properly. I think this unit is circa 2006 as it has the Freescale logo in place of the Moto 'M'. I thought I was going to need a heatsink, but the top of the package doesn't seem to break 40C under load.

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I wonder how difficult it would be to replace the processor on a 550c daughtercard with a newer model. Its current processor is one that is period correct, so it generates quite a bit of heat. Something cooler would be nice.

Edited by Paralel
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The newer models are made with a newer mask, meaning they draw less power, generate less heat and should be more overclockable. Most people say they get warm but not hot to the touch, even without a heat sink. Since I want to run mine at 50 MHz 24/7/365, I want the coolest, most stable one possible.

 

Paralel: Yes, you can. They're cheap, too:

 

http://www.ebay.com/itm/MMPN-C68040FE25-Manufacturer-MOTOROLA-Encapsulation-QFP-32-BIT-W-CACHE-MMU-/181813260936?hash=item2a54ea3288:g:x5UAAOSwT6pVkfVg

 

Make sure you get an MC68040FE without a "V" at the end. The "V" signifies a 3.3 volt chip instead of 5 volts. You'll have to find someone who can desolder and resolder a 184 pin QFP chip.

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