What is the maximum temperature a 68040 can tolerate?

[Gulliver]

What is the maximum temperature a 68040 @40 mhz can tolerate?
I already read the 68040 users manual from Freescale, but then there I could not find the information I need. I want to know this since I plan to overclock it and measure its temperature with a digital thermometer with an alarm so as to know when I am reaching the absolute limit, and then stop, before I kill it.
The other thing is, where on the 68040 should i put the temperature sensor? Is the heat conducted evenly to the entire chip enclosure, or does it get hotter on the center?

[the_leander]

What is the maximum temperature a 68040 @40 mhz can tolerate?
I already read the 68040 users manual from Freescale, but then there I could not find the information I need. I want to know this since I plan to overclock it and measure its temperature with a digital thermometer with an alarm so as to know when I am reaching the absolute limit, and then stop, before I kill it.
The other thing is, where on the 68040 should i put the temperature sensor? Is the heat conducted evenly to the entire chip enclosure, or does it get hotter on the center?

40Mhz is the fastest you can push an 68040 without the need for exotic cooling methods. They're just not stable beyond that.

Tbh mate, any overclock you put on it would be negligible at best. If it's working and its stable, leave it alone. Trying to crank it up to 50Mhz is a sure fire way of causing the magic blue smoke to escape from it.

[bbond007]

What is the maximum temperature a 68040 @40 mhz can tolerate?
I already read the 68040 users manual from Freescale, but then there I could not find the information I need. I want to know this since I plan to overclock it and measure its temperature with a digital thermometer with an alarm so as to know when I am reaching the absolute limit, and then stop, before I kill it.
The other thing is, where on the 68040 should i put the temperature sensor? Is the heat conducted evenly to the entire chip enclosure, or does it get hotter on the center?

I would venture to say the actual point of failure will vary chip-to-chip.

I think a better question would be - what is the fastest stable speed you can over-clock an 040. I do know PP&S factory over-clocked the 25mhz part on my accelerator to 28mhz and that board was very stable.

Lets just say the 040 was not know for being real overclockable... 060 will take over-clocking more reliably than a 040.

[Gulliver]

Thanks guys, but I was asking about temperature, not mhz. I know what I can do and where to push the limits regarding speed, what i dont know is what is the maximum heat the chip can tolerate without dying, and this is very important, because according to that information, plus a few tests with my digital thermometer, I can find out the most efficient way to cool it.

Let me explain it easily: My particular 68040 can work at 50 mhz. But I am using a huge heatsink and a really enourmous fan, plus some other secondary fans. The thing is that I want to reduce the amount of cooling to a point where the 68040 can still work without burning, and I can finally close the tower, which is something I cant with all this excessive cooling. So I want to adjust the 040 cooling and for that i need that information.

[matthey]

From 68040 User Manual Section 11...

Maximum Operating Junction Temperature 110°C

You should read all of Chapter 11 as it has more information. The manual can be downloaded here...

http://amiga.serveftp.net/datasheets.html

It's called a datasheet on this site but it's the same thing.
I wouldn't try to push overclocking the 68040 too much and that's with excellent cooling. Some of the later 68040 masks were pretty overclockable and some of the early ones would barely do 40 MHz. It's better to convert to a 68060 and get one of the newer mask 68060's and you have something 3 times as fast and cooler than any 68040@40MHz .

[Gulliver]

I have already read that section 11, and about that junction maximum temperature of 110 degrees celsius. And as I understand it, the maximum junction temperature is much higher than the maximum temperature at the ceramic chip enclosure, which is the onlyone I can measure.

It is allways better to convert to a 68060, but that is possible on Apollos and Blizzards, and not every 040 accelerator.

[Minuous]

This info should be in the relevant datasheet. If it's not, you could email Freescale and ask why they are making incomplete datasheets, and what the maximum operating temperature is. If they get enough such requests they might even update their substandard documentation.

[Gulliver]

You are right on that one!
For example the 68040 user manual on chapter 11, where it speaks about the thermal characteristics of 68040 processors, it explains the temperature the 68040 with and without cooling, but only on 25mhz and 33 mhz models. It seems as their user manuals are way too old, and havent been updated since before the creation of the 68040 at 40 mhz!

[ElPolloDiabl]

The ideal place to measure temperature would be underneath, next best place would be directly on top. The max temperature would 60 degrees celsius, I'm pretty sure all CPUs fail after that.

[Gulliver]

@Fanscale
60ºC then.
Now on the measuring place, can it be on the side of the chip. The problem is that heatsinks will be ont top of the chip, so no place. Underneath the chip there is no place, as the socket and the soldered pins prevent that from happening. Would that be okay?

[johnklos]

It doesn't work like that exactly. A cool chip will be stable at a higher clock speed than a hot chip. If you run the chip at almost the top of the thermal envelope, you'll be lucky to get it to run at its normal clock speed.

With regards to overclocking, remember that a majority of all of the m68040s made in the early and mid 1990s were all the same mask meaning that a 20 or 25 MHz marked chip is identical to a 40 MHz marked chip. I have overclocked dozens of 25 MHz CPUs to 40 MHz without ever a problem. Of course doing so requires adding a heat sink if there isn't already one.

I have a bunch of QuadDoublers which run at 50 MHz and they all work fine. They have heat sinks and some don't even have fans - just some air movement from the power supply fan is enough.

The biggest problem I've seen with overclocking m68040s is with the clock generator. Replacing a MC88920 with a faster-rated MC88916 is usually a good solution, but only if you're having stability problems.

Some of the Amiga accelerators which can take either an m68040 or an m68060 have completely different clock generators which can run much faster. In that case, if you find a new mask m68040, you should be able to run your CPU much faster - perhaps 66 MHz or more. One of these days I'll find one and give it a try.

[Gulliver]

@johnklos

It is not that I am going to use it without cooling, but it is about how much cooling do I need for not killing the chip and being able to close my tower setup
I plan on using an aluminum/copper heatsink with a fan on it that provides 4.5 CFM. That should fit my tower, but then will it keep the 040 cool enough not to die?
On the othe hand, It should be pretty interesting if you could tell me what is the fabrication mask of the 040 of the QuadDoublers you are using, and what cooling solution they have.
I am using the worst MC68040 mask there is (E42K) from 1995. But at least that is better than any XC68040 part.

I am going to check which clock generator I have, just to be on the safe side.
UPDATE: Just checked it is a custom clock generator as I have no plastic SOIC chips on the accelerator.

Thank you for your advice!

[Zac67]

Don't forget that both higher clock speed and higher temperature (plus higher voltage) increase electromigration, thus lowering the life span of your '040.

The most accurate place to measure temperature would be center (or close to) of the chip package, directly above or below the die. Since top center is also the most crucial point for cooling you'll have to settle for somewhere on the side, immersing the sensor into the heatsink.

[delshay]

if and when i find time i will overclock 68040v ( 3.3v version ) to check heat output.

iv not read the docs on the 68040 but the 68060 has a thermal sensor built-in which i find amazing no amiga user(s) have tested.

[Stedy]

Hi,

Based on 8W of power @ 40Mhz, the maximum temperature, measured on the case would be 85C. There is a Junction to case thermal resistance of 3 C/W so in use the case heats up by 24C , so you simply subtract this self heating from the maximum device temperature to get the safe temperature on the case.

The hotter a part gets, the slower it operates. Depending on the design, this may causes stability issues. Cooler is better.

@Gulliver

Look at some of the new pin shape CPU coolers, they are amognst the most efficient on the market. In a towered A1200, you should have ample room for a taller heatsink. If you can fit one of thses, you may be able to reduce the number of cooling fans.

Worht looking at this software, http://www.heatsinkdesigner.com/

@Delshay.

The Maxim 1617 will read the thermal diode and provide a temperature reading via the I2C bus.

@Fanscale

I have run the MPC8458 @ 1 GHz at a junction temperature of 105C, for 24 hours with no issues. Intel/AMD cpus might expire but the Freescale/Motorola ones are hardy.

Ian