Yes, if you have a regular case with a PSU with a fan, there should be enough airflow for a 486DX-33. These were some of the last CPUs to not require any heatsink or fan.
I don't think there is a way to monitor CPU temperature with software. This requires a temperature sensor in the socket, which simply wasn't done yet back then (temperature was not an issue). I believe that started in the era of Pentium III/Athlon CPUs. Later CPUs have the sensor integrated (it is required for throttling/failsafe shutdown).

If a heatsink/fan is required, it is normally written on the CPU. However, even if it can run without cooling, I don't see any reason to do so. The hotter it gets, the shorter its lifespan will be. If you don't want noise, at least a heatsink should be installed.

the DX33 needs a heatsink - it may not be written on it, but it does get hot, especially in regular baby-at cases.

Thanks for the answers ! I'm trying to install heatsink.

kanecvr wrote:

the DX33 needs a heatsink - it may not be written on it, but it does get hot, especially in regular baby-at cases.

I picked up an OEM system a few months back, and it was just the bare 486 DX-33, no heatsink. Case is a standard baby-AT case.

Album of it here:
https://imgur.com/a/jBGyr

kanecvr wrote:

the DX33 needs a heatsink - it may not be written on it, but it does get hot, especially in regular baby-at cases.

Yeah, I have a DX33 in an OEM build, and it didn't come with a heatsink, nor does it strictly "require" one. It does get pretty toasty though, so in the interest of life extension I put a heatsink on it... no fan though.

Technically any 486 CPU bellow 50Mhz. does not require a heatsink. But heat is a big enemy of electronics so it would be nice to have some cooling.

What I do with older systems not intended to have passive/active cooling systems (heatsinks/fans) it's use double sided velcro tape to fix a fan to the case in front of (or as near as possible) the CPU. Using velcro tape makes easy to remove it if needed. You can use a fan from an old Pentium/K6 cooler or from a PII(I)/K7 since these fans are usually ball bearing so less noisy that older ones. You do not need a 'monster' fan so pick up whatever you have at hand.

I have used this method to cool 286 (NMOS), 386@40 and a 486@40 (Socket2) with very good results.

dieymir wrote:

Technically any 486 CPU bellow 50Mhz. does not require a heatsink. But heat is a big enemy of electronics so it would be nice to have some cooling.

You should see things in the proper perspective though...
A 33 MHz 486 has a TDP of 4.5W: http://www.thinkwiki.org/wiki/Intel_486
4.5W isn't exactly going to generate much heat. It's nothing like the CPUs we use today, where a CPU of 70W TDP is considered 'low power'.
Just look at the heatsink they put on the 486DX2-66... Just a tiny heatsink, no fan required. And that one was 6W.

TDP isn't really important, since you need to keep die size and transistor count in mind. It still get's very hot and heat must be dissipated. Otherwise, hot spots may emerge which can kill the CPU.

Also, modern CPUs are working completely different. They can put unused parts into sleep, change voltage, clock frequency, etc.

derSammler wrote:

TDP isn't really important, since you need to keep die size and transistor count in mind. It still get's very hot and heat must be dissipated. Otherwise, hot spots may emerge which can kill the CPU.

4.5W is like a tiny light bulb, like the ones you use in a bicycle. Really, it's no big deal, certainly not for the die size of a 486.
Transistors can generally take up to 90-95C before they even start malfunctioning (which doesn't kill them, just crashes the system). A 486DX-33 simply doesn't get that hot. Even if it has been running for a few hours, you can still touch it.

derSammler wrote:

Also, modern CPUs are working completely different. They can put unused parts into sleep, change voltage, clock frequency, etc.

They do now, but worst case, say in the days of early Athlons, there was little or no throttling, and even when 'idle' they would often use 60W+.
These CPUs would burn up in a matter of seconds if you took the heatsink off.

My Commodore 486DX-33 doesn't have a fan and it looks like it never had one so I think you are safe

power consumption is not directly related to heat dissipation. Touch a DX33 w/o a heatsink after it's been on for an hour - it does 70-80C. It may not be needed, but it is recommended. A fan is optional.

I'd like to point out that we are talking about an Intel 486DX-33 here.
Other brands may run hotter (back then it was a good way to lower prices: tighter binning of the dies, then adding a cheap heatsink and/or fan, basically a 'factory overclock').

Officially, all 486 CPUs up to the DX2-66 are manufacturer approved to NOT need a heatsink. You can of course put one on there, and it may even extend the lifespan of the chip, however silicon really only gets unhappy with the heat at around ~90-100C. This is very hot, so much so that if you were to touch the CPU, you would burn yourself instantly, so if when you touch the CPU and you do not burn yourself instantly, it's likely not hot enough to boil water.

I have seen tons of OEM systems with 486 chips in them that have had no heatsinks nor fans of any sort, and most of them run fine to this day. Personally, a DX-33 is nowhere near powerful enough to warrant a heatsink. You can put one on there, but through official specification, de-facto OEM processes, and my personal experiences, you do not need to do so in order to have it run at a reasonable temperature.

Do you guys just buy thermal epoxy and just glue on a small heatsink?

Any processor can be helped with a heat sink, even an 8088. Heat sink adhesive is pretty cheap, along with heat sinks. I've yet to in-sink-erate any of my oldputers, but it sounds like something amusing to do on a day off. Alas, installing ventilation fans into older devices not made for them, is often a sin, as it often requires marring of the case.

dexvx wrote:

Do you guys just buy thermal epoxy and just glue on a small heatsink?

you can attach a small socket 7 or video card heatsink using a paper clip.

The good heatsinks that can be removed if wanted sort of clip onto the CPU with plastic clips.

I honestly wouldn't spend money on it. The chip won't fry without a heatsink, there are thousands upon thousands of examples of it living a long decent life without a heatsink. If you are worried about heat, a fan might actually be a better idea as it's easier to mount, and you likely already have one you can throw in.

kanecvr wrote:

dexvx wrote:

Do you guys just buy thermal epoxy and just glue on a small heatsink?

you can attach a small socket 7 or video card heatsink using a paper clip.

Drawing a blank, got a pic?