It's not required, but probably recommended. I ran a DX2-66 without a cooler from 93-97.

Standard Def Steve wrote:

It's not required, but probably recommended. I ran a DX2-66 without a cooler from 93-97.

Would you recommend just a heat sink or a sink/fan combo?

A passive heatsink would be more than enough. My DX2-66 ran completely naked for years.

Standard Def Steve wrote:

A passive heatsink would be more than enough. My DX2-66 ran completely naked for years.

I found one that had a fan anyway, so put that on there. Probably don't need thermal paste in the case I assume?

Thermal paste probably isn't necessary, but I'd use it anyway just because there's no reason not to (it's practically free and doesn't make any noise or transmit vibration). My attitude with old hardware (or anything I want to keep for a very long time) is to try to cool it more than I would have in the 90s, because we're asking it to live longer than anyone intended and it's only going to keep getting harder to replace.
It's hard to hurt a CPU but dissipating the localized heat probably makes the motherboard components happier.

Back in those days I had a 5V DX2/66 with just a small passive heatsink with no paste and the clip arrangement didn't put any real pressure between the pieces. It was hot to the touch but at the time I didn't think much of it. To be fair the motherboard was unstable so if there had been any heat induced crashes I wouldn't have known the difference.

No thermal paste for dx2's though I would recommend at least a heatsink.
I have a passive cooled dx2-66 from an IBM PC-300. Ok solution.
Preferable I go for heatsink and fan personally.

if its a 5v model then it does, usually generating more than 6 watt which is twice of the amd5x86-133.
it burnt my finger when i tried to feel it, and even a 3 watt amd5x86-133 with active fan still feels a bit hot although safe.

depending on how snug the heatsink fits, the thermal compound could at least ensure good contact. I use it for just this reason--my clip-on HSF jiggles pretty loosely without it.

rick12373 wrote:

Do I need a heat sink or a heat sink/fan for a 486 DX2 66Mhz? I did not think it was necessary. But I was experiencing a weird issue where the mouse was not working any more. The machine had been on for a while. When I touched the CPU it was quite hot. I left the machine off for a while and turned back on and the mouse was working again. Weird.

Not entirely weird. My Cyrix DX2-50 ran without a heatsink and I could see a notable performance hit when playing Wolf3d (very choppy framerate). Once I installed a heatsink and fan the system ran very happily. Like everyone has said here, it wouldn't hurt to add a fan, and me being quite OCD about cooling (and wire management), I would suggest the same.

The only experience I have with a dx2-66 is the one that came with my DEC Venturis. It came with a passive heat sink installed. Whether or not it makes a difference is a matter of opinion.

Just slap on a passive chipset cooler with a thermal adhesive pad and you are good to go, the cheap stuff works well and nothing too fancy.

Rule of thumb:

Minimum:
3.3V Clean
5V Passive

Normal:
3.3V Passive
5V Active

Safe:
All Active with paste!

Lower life or reliability, if you use 5V 66MHz cpu without cooling!

rick12373 wrote:

Do I need a heat sink or a heat sink/fan for a 486 DX2 66Mhz? I did not think it was necessary.

For early Intels, you only need a heatsink.
For early AMDs, you also need a fan.
It actually says that on some of the chips:
.

For later CPUs (3.3v models), you may be able to get away without even a heatsink.

Due to their age, I even installed a heatsink and fan on my 486DX 33 MHz (though not required). However, a heatsink is probably enough to keep it cool.

If you want to ensure stability and a longer life for your 486DX2 66Mhz, I would strongly suggest a heatsink & fan.

The AMD chips run hotter because they basically binned them lower than Intel to get the prices down.
Basically what Intel binned as a 486DX2-50 + heatsink was binned as a 486DX2-66 + heatsink/fan for AMD.
Which makes sense I guess... the difference in yield made it cheaper to just add a fan.

The Am386DX-40 is probably a similar story. I bet the later Intel 386DX-33 chips could easily clock to 40 MHz as well. But it would cut into 486 sales, so Intel wasn't interested.

Just to give you an idea, my first 486 in 1994 was a Cyrix DX 33, and during that time period for these CPU's heatsink/fan was not even being considered. When I upgrade to an AMD DX4 100 in 1995, it was already common practice to put both a heatsink and fan on top of every 486 CPU. My latest 486 class CPU was a Cyrix 5x86 100, in early 1996, and it came only with a (nice and green) passive heatsink (I also added a small fan on top of it because I was forcing it to 120 MHz).

As a side note, my tiny little soldered-on-board Intel 386SX-16 in 1992 was running so hot, any touch on it, a couple of seconds long, would definitely result in a blistered finger. During that time, nobody was even talking about CPU cooling. It still works today, in spite of the fact that for the first 2 years of its life, it is mostly used with FORTRAN number crunching jobs, numerical analysis programs that runs several days without break.

All things aside, as all the other people already said before me, it is just common sense to use heatsink, fan and thermal paste for any 486 CPU, because it reduces the heat fatigue on the CPU and it cost next to nothing.

For what it's worth, I've been using a totally bare DX2/66 -- no heatsink, no fan -- in a Compaq Presario CDS 510 (exactly like the system in your signature, but came stock with an SX33) for probably a year now with no issues whatsoever. As you know, it's pretty airy around the motherboard in the back of this system so I'm not too worried.

This is an Intel chip which I got brand new from eBay. I forget when it was made but well into the 00's at least, so I assume with the benefit of modern production it's less likely to be heat sensitive than early models.

A DX2/66 though is the very last processor I would run without a heatsink. As soon as you're into DX2/80 or DX4/100 territory it's heatsink at least and probably a small fan, too.

I remember back in college a friend of mine had a K6-2 processor with just a small fan on it, but the inside of his case was getting pretty hot. So I remember him and I, we found some styrofoam and made a conduit, then taped it to the front fan housing so that all the cold air from outside the case would be funneled directly onto the CPU fan/heatsink. His CPU temps dropped over 10 degrees F.

Scali wrote:

The Am386DX-40 is probably a similar story. I bet the later Intel 386DX-33 chips could easily clock to 40 MHz as well. But it would cut into 486 sales, so Intel wasn't interested.

The Am386DX-40 gets barely warm (as opposed to a 486DLC). AFAIK, it differs from the intel ones by using a static CMOS design.
I'm not 100% sure, but I think it can also safer underclocked because of this (higher stability).
https://en.wikichip.org/wiki/amd/am386