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?

[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.

[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.

[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!

[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?

[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!

[Gulliver]

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.

Ian

Thanks, it is easier and safer to know where I stand.

@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/

Ian

I will use then one of those coolers. That Heat Sink Designer software seems rather good, I will give it a try.

Thank you