So this is an actual 5x86 heatsink+fan from a system that I unfortunately didn't keep much else of. Notice, no thermal compound back in those days.
Notice the heatsink has tiny clips that actually go underneath the cpu package - just not far enough to touch any pins and short anything out.
I have a 5x86 chip ready to go whenever I find a motherboard for another build. I'm looking for a UM8881F with Award BIOS, such as the famous Biostar MB-8433UUD-A, or EFA 486U-PIO/A, or another from the AMD 5x86 compatibility list, but finding one has been tougher than I expected. There are some similar ECS boards on eBay right now, but those have no PS/2 mouse.

I'm intrigued by the superGRIP heatsinks from Advanced Thermal Solutions. It seems they have a 45x45mm one that would clip right on to a 486 chip. In particular, as discussed in this thread 486DX2 heat sink debate some of the ATS heatsinks are so big that so long as they don't get in the way of anything else on your board, they appear to provide lower thermal resistance with no fan than what AMD specified as a heatsink+fan on the 5x86 datasheet. So, using one of those big heatsinks you may not need a fan.

Thermal adhesive pads are pretty much junk. You definitely want a clip-on style cooler.

If you can't find something you like, you can always just get something and then use fishing line or something like that to hold it in place by running it through the fins and under the CPU.

Something that would most likely work really well would be to jerry-rig a laptop heatpipe cooler to it and then wire up the fan with a fan controller or even a simple POT setup so you can adjust the speed.

I had done exactly like that with string before back in the day when I had PC built newly and didn't think of getting the heatsink. 🤣, didn't work too well with what I had found in my electronics junk stash that I bought along with me when I was attending College. The Am486DX-40 crashed easily, and really needs heatsink.

When I did get proper heatsink with the horrid little fan which was just a typical cheap stuff, later on bought the Dynamite VLB card and overclocked that cpu to 50MHz and it was like this way for rest of it's life.

Thank you for showing photos. I wanted to see the hooks design first. I can make one once I know what to do.

I had enough with plastic clips, these usually break, some is so sloppy that does not exert any force at all. The one that were best was four little G clips that comes with heatsink was better quality that you press them one by one onto CPU while heatsink is held to it, haven't seen any since. These G clips is cross section design as you hook it onto heatsink, then press inwards this which wedge them onto cpu which did exert good force due to G shape acting as very stiff spring.

Aha, found this while googling something else. That's the G clips design!

https://www.worthpoint.com/worthopedia/ast-48 … rd-n-1807830633

Cheers,