If you happen to find this style of heatsink/fan
http://www.suntekpc.com/htm-2/fnc-486-cpu-fan … or-dc1204sm.htm

The fan in this design traps the heatsink when clipped to the CPU in normal use.... not being normal, I have slid out the supplied heatsink and mashed the fan down on top of the fixed sink on cyrix 486, where it holds on well.

Trashbytes wrote on 2023-12-22, 15:55:

its a 486, it was designed to run like that with passive heatsink cooling in a case with little to no air flow for years, its no […]
Show full quote

AlessandroB wrote on 2023-12-22, 15:31:

I have the hexact cpu in my collection and i can say that using it, become hot like a Sun, the only think is that intel do not think that cpu will survive so many years, they think that this dx2 must be replaced and recycled in 3/4 years maximum. Using it for years and years must destroy it, i can't belive it can survive for years at this temperature. If you touch it literally you burn your finger after only 10 minutes.

its a 486, it was designed to run like that with passive heatsink cooling in a case with little to no air flow for years, its not a modern CPU with a 250watt TDP that will die the moment it hits 105c. I grew up with 386 and 486 machines and they are unkillable from heat so long as they have some form of passive cooling or even just air flow from a case fan.

The 486 DX-33 doesn't even need passive cooling, I know it seems foreign to run them that way but its perfectly fine and what conditions they were designed around, adding a case fan near them for a bit of air flow is all that's really needed. IIRC it wasn't till the DX2- 80 and DX4-100 that they needed some form of small fan on them to supplement the passive cooling.

Just for reference 50c will burn your fingers and a cup of hot coffee will also burn your fingers and both are well below 100c, the 486 DX2-66 is fine up to ~85c with nothing more than its heatsink and basic case fan airflow. (It wont ever hit that temp, thats what the heatsink is for)

As for what Intel wanted . .well these CPUs were normally used in PCs at a time when you didn't just go out and buy an upgrade every 2 - 3 years. .CPUs were very expensive at the time so Intel didn't have a reason to do what you suggest and the 486 CPUs were built to last under a variety of stressful conditions . .like being in a dusty case with little to no airflow in some server closet running at high temps.

Agreed. My 486DX-33 doesn't even run that hot. I can still touch it with my finger . Perhaps what might also help with these Overdrive CPU's is that they are 3.3V CPU's and not 5V.

My Cyrix 486DLC-40, on the other hand, runs very hot (too hot to touch). When I bought that CPU, I always had a 486 CPU fan mounted inside the case with air just blowing over the CPU.

zuldan wrote on 2023-12-23, 08:23:

dominusprog wrote on 2023-12-22, 12:44:

If you plan to put the board inside the case, install an 80x80mm jet fan at the front.

https://www.delta-fan.com/AFB0812SH.html

The fan mounting holes in all my cases are 70mm by 70mm apart. Any idea if this fan would fit that?

Check this one out. And keep in mind that you can use a DC/DC module (or build one yourself using LM317 regulator) to decrease the voltage.
https://www.delta-fan.com/aub0712hh-c.html

Usually I'm from the camp that sticks a fan in to the bottom of the case, pointing at the CPU and make sure the air gets there.

Technically it's not take necessary but I like to keep things cool. I even put a sink on a SX25 and have extra fans in a 286 :p

As I'm currently do a 486 DX4-100 overdrive build, thought I'd share my own cooling solution.

Because the case I'm using doesn't have a good place to mount an internal fan, I opted to put a 40mm fan onto the heatsink itself in a side-mount configuration. This moves air better through the fins under the flat metal top of the heatsink.

It's way more cooling than it needs, but it definitely won't be overheating.

Cool. It reminds me of a construction from the 80s.
In a PC magazine, there was a prototype of an overclocked 286 PC on the testbench.
The CPU cooling was done by using cardboard. The cardboard worked like an air tunnel that ended in a big 80mm fan or something.

Shponglefan wrote on 2024-01-01, 02:56:

As I'm currently do a 486 DX4-100 overdrive build, thought I'd share my own cooling solution.

Because the case I'm using doesn't have a good place to mount an internal fan, I opted to put a 40mm fan onto the heatsink itself in a side-mount configuration. This moves air better through the fins under the flat metal top of the heatsink.

It's way more cooling than it needs, but it definitely won't be overheating.

Thanks for the great idea! This is the solution I went with. Purchased the exact fan.

zuldan wrote on 2024-01-05, 11:18:

Thanks for the great idea! This is the solution I went with. Purchased the exact fan.

Glad to be of help! Hope your own build goes well! 😀

Shponglefan wrote on 2024-01-05, 16:18:

zuldan wrote on 2024-01-05, 11:18:

Thanks for the great idea! This is the solution I went with. Purchased the exact fan.

Glad to be of help! Hope your own build goes well! 😀

CPU fan now installed (Noctua 40mm NF-A4x20 FLX). I also managed to install a Noctua 80mm NF-A8 FLX behind it. The 80mm fan pulls in fresh air from outside the case and blows it onto the back of the 40mm fan. Total overkill but the CPU went from 57c to 28c. Hopefully she'll last forever now 😉

Nice work! The fan looks like a A4x20 btw. How silent is it?

PD2JK wrote on 2024-01-06, 09:10:

Nice work! The fan looks like a A4x20 btw. How silent is it?

Oops you are correct. I copied pasted the wrong model.

It’s silent. You can use the cables supplied with the fans to turn down the RPM even further to lower the noise but it’s pretty quiet as it is.