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80286 temperature

M

mkemp

Experienced Member
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I've just about gotten my tricked-out XT-286 finished. When I had it running for a while I noticed that the CPU and FPU are hot to the touch, too hot to keep a finger on.

The XT-286 is running the stock 6mHz and both the 286 and 287 are marked as 10mHz parts. Should I be concerned? I can dig up heatsinks for both, and a fan for the 286.

I have another board I've tested with both 6 and 8mHz chips - the board doesn't "light up" and the chip gets really hot, I haven't tried the 10mHz in that board or the 6 or 8 in this one.

Both +5V and +12V from the power supply are okay. I might figure out which 286 pin is Vcc and measure that.

Any thoughts?
 
Assuming that your PS isn't cranking out over the limits, I'd say you are okay. I have several 486's that will get your pinky warm - one needs a fan the other doesn't.
 
My 286-10 ran happily for 20 years. It was mildly hot; hot water from tap temperature not up to boiling or skin burning. Thus, the XT-286 should give you many more years of operation.

However, if you have the heatsinks available, adding them won't hurt the system any.
 
I think it's normal, and there's no need for a heatsink on a 286. Not even 386DX's come with heatsinks!
 
Thanks to all who replied. I think I'll just stick heatsinks on the CPU and FPU and forget about fans for the moment.
 
Heatsinks are not necessary on these chips, they run hot and this is normal. Silicon is just fine far outside of temperature ranges that would be comfortable to humans. As long as it isn't over 70C or so I wouldn't worry about it, and if it is then something else is wrong.
 
For some reason I can't seem to find an Intel spec sheet for this, but surely there must be one. Modern processors are rated in the 60°-90°C range, and some go to 100°C. That is for what they refer to as critical case temperature. Presumably the core temp is allowed to be considerably higher.

My feeling is that a super conservative company like IBM would have put a heat sink on its 286s if it was even remotely possible that it would make a difference.
 
HAaaa hahahahahaha... I WORK for IBM. The only area where they're "super conservative" is financially. (and mainframes)

I'm afraid the PC division (when it still existed) was the same as any other volume manufacturer. If the 286 will run without the heatsink, and the heatsink has a cost... it's a gone burger.

If you can find one to fit it, and can fit it properly (i.e. no airgaps in the thermal grease to cause build-up) then absolutely, fit it. It will extend the life of this vintage system.
 
Gibsaw said:
. . . If you can find one to fit it, and can fit it properly (i.e. no airgaps in the thermal grease to cause build-up) then absolutely, fit it. It will extend the life of this vintage system.
Click to expand...

That is a sensible reason.

Life extension ... hmmm. Maybe I'll get myself one of those hats that you put ice in. :D
 
Buy a small stick on heat sing for bout $1.50 and it will absorb the extra heat and cool off with air flow, such heat sinks are commonly used inside digital cable boxes and what not, they dont require mounting or and glue, they just stick on.
 
gerrydoire said:
Buy a small stick on heat sing for bout $1.50 and it will absorb the extra heat and cool off with air flow, such heat sinks are commonly used inside digital cable boxes and what not, they dont require mounting or and glue, they just stick on.
Click to expand...

The OP has an XT-286 box; air flow is pretty minimal.
 
According to the data sheets on the 80286 CPU as published in the Intel Microprocessor and Peripheral Handbook (page 3-38) the 80286 CPU (-6, -8, -10, and -12 parts) has an absolute maximum ambient temperature under bias rating of 70 degrees C. Later on page 3-71 it quotes a maximum case temperature of 85 degrees C.

The table states:

"Notice: Stresses above those listed under 'Absolute Maximum Ratings' may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability."

The data sheets for the Harris/Intersil 80C286 give the same operating temperature ranges, but the maximum package power dissipation is listed as 2.2W for the PLCC package and 1.22W for the PGA package (this is with clock speeds of up to 25 MHz), as compared to the Intel 80286 which lists a maximum power dissipation of 3.0 watts.

The Intel 80286 is clearly capable of operating in the 'too hot to touch' range.

Sean
 
ISTR that the PC XT 286 used a 6MHz part, and the PGA package. (I could be in error).

At 6MHz an 80C286 is loafing and probably would be barely warm to the touch.
 
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