5v version here

Yes it seems to depend on the revision of the CPU. I would recommend at least a heatsink on all 486 DX2s.

i suggest using one, intel 486dx2-66s are all 5v models and consumes ~6.6watt, which is considerably hot.

retardware wrote:

Even an (Intel) 486/33 gets so hot when idling in DOS that one cannot touch it for long.

AFAIK, DOS is never really "idle".

It's not a multitasking OS, there is no concept of idle time. It's always doing *SOMETHING*.

looking at that picture what's the difference between amd dx266 and dxL266? they look very much the same except the L

SquallStrife wrote:

retardware wrote:

Even an (Intel) 486/33 gets so hot when idling in DOS that one cannot touch it for long.

AFAIK, DOS is never really "idle".

It's not a multitasking OS, there is no concept of idle time. It's always doing *SOMETHING*.

Good catch 😉

The article of that Ben from Microsoft is funny though 😀

Ben from Microsoft wrote:

So when DOS is sitting at the command prompt ‘doing nothing’ it is actually in a very tight loop of code which is responsible for blinking the cursor and checking for new user input.

In other words, the processor probably is executing a loop from its cache, actually using only small parts of the chip.
Maybe I should attach a temperature sensor and measure the results in the "very tight loop" and in Prime95 or the like.

But I do not understand what Ben wants to say with "blinking the cursor", because this is done by the CRTC. 😀

treeman wrote:

looking at that picture what's the difference between amd dx266 and dxL266? they look very much the same except the L

That's early 3V3 devices from AMD. Later they've changed the product code to include letter V (like Cyrix did and all their clones/copies) to indicate it's a lov-voltage CPU.
Note, there are 386DXL devices as well but AFAIK these all run on 5V, except due to a design tweak and removal of dynamic logic (and addition of SMM) can be clocked down to zero Hz to save power.

I think the486DX2-66 was at the limit between "no fan required" and "fan required".
Depending on the manufacturer, voltage and other factors it fell in one of the groups.
Personally, I'd just install a generously-sized passive heatsink as a precaution.

So when DOS is sitting at the command prompt ‘doing nothing’ it is actually in a very tight loop
of code which is responsible for blinking the cursor and checking for new user input.

The idle loop thing is true, but I don 't know exactly if the cursor thing is as well (on VGA).
I vaguely remember that CGA/Hercules cards did handle the blinking on their own.

For DOS, there's Power.exe and DOSIDLE (third party).
Both can detect idle loops and put the processor to sleep - either by APM BIOS calls or by directly issuing the HLT instruction.
Not sure how well this works for games, though. I always use them for VMs, however.

For Windows 3.x, there's also a device driver (WQGHLT) written by Weiqi Gao.
It works on ~486+ machines (maybe 386SL, too).

Installing heatsinks on 486 CPUs is a hassle, brackets and heatsinks made for those prackets are always difficult to obtain and I don't want to use thermal adhesive tape that is a BITCH to remove afterwards on my previous vintage CPUs 🙁 Shame, really.

My 486DX2-66's run fine without a fan.

It runs a bit hot, but that is not really a problem at all.

Don't forget that 486's use a very coarse lithography, at ether 1um or 800nm. Such coarse lithography is not as subject easily failure by electro-migration from running HOT.

However, I did sodomize my AMD 133mhz 486 processor by gluing a heatsink and fan on it, because finding compatible fans and clips is almost impossible.

have also ran a couple of DX2 66 without a fan or heatsink and they were okay

If speaking of the 5V DX2-66, then a fan OR a heatsink is required. You don't need both, but they usually had both anyway. In my opinion, running without any cooling is a bad idea, unless you have a 3.3V model. The DX-50 and the DX/2-50 usually had cooling as well. DX-33s do not require active or passive cooling under normal environmental conditions. If there was a "borderline" chip, it would have been the DX/2-50. I never really used those though because they had a gimped 25MHz bus, but I always put heatsinks on my DX-50s. I would assume both of the 50MHz chips have similar thermal specifications?

My thoughts: If this was 1994/1995, then we could probably debate whether a heatsink and/or fan is required for a 486DX2-66 but, in 2019, I would say install at least a heatsink if you wish to prolong the life of your chip. These are not manufactured anymore and are become more rare every day.
Like brostenen, I actually have a heatsink and fan installed on my 486DX-33 as well.

Heatsink's with or without a fan are always to be found on eBay. Not like there is nothing to be found at all.
Like this one.

EDIT:
And there are a few more, both North America and Europe....

appiah4 wrote:

If it's a 3.3V model (AMD, Cyrix etc.) you can get away without a heatsink. For the 5V Intel models if it's a regular ceramic cpu you need a fan inside the case or a heatsink; the overdrive intel cpus come with permanent heatsinks so those are just plug and play.

Depends.
On a 3.3 V AMD ADW I recommend to use a heatsink and fan too.
On a 3.3 V AMD ADZ you may not need cooling. But i recommend it too at least when you are overclocking it.

I've put heatsinks even on my 386DX40 CPUs just because they felt a bit too warm for my liking.

There's no reason to keep them naked. So don't.

retardware wrote:

But I do not understand what Ben wants to say with "blinking the cursor", because this is done by the CRTC. 😀

Jo22 wrote:

The idle loop thing is true, but I don 't know exactly if the cursor thing is as well (on VGA).
I vaguely remember that CGA/Hercules cards did handle the blinking on their own.

Yeah, the text mode cursor is done "in hardware". I don't know why he would've said that specific thing.

I don't want to use thermal adhesive tape that is a BITCH to remove afterwards

Just use adhesive on CPU corners and fill the center with thermal paste. But from my personal experience good thermal paste can provide enough surface tension between rough ceramic and small aluminum radiator/cooler even without adhesive.

I've had 5v 486dx2/66 with and without fans. No problems with either.

The 486 DX2-66 Overdrive only came with a tiny little heatsink with no fan. I found that it would overheat after a short while and crash programs, hang, etc. Maybe they intended it to have passive airflow through the heatsink somehow, because it's inadequate on its own.