I may be lucky then. I got it up and running at 120Mhz only needed to decrease the RAM timing to Fast (instead of Fastest). What are you suggestions feipoa on the longevity of this setup? I believe the chip is running at 3.3/3.45 or at the most 3.6V (I don't know exactly because of the missing motherboard manual) with a standard heatsink and fan (currently without thermal compound). Would it be OK to use it for an extended period of time with these settings? It performs quite well anyway, 3DBench gives me exactly 100 points (or cannot display more) and Speedsys shows these results.

Thanks debs3759 but the battery seemed to be functional (it stored 4.1V fully charged and held the CMOS data) the problem is it caused some issues with the clock so it had to go. It might be a faulty one though so I will experiment first with external battery and then maybe add a new internal one.

If you are overclocking without thermal paste, you processor is at high risk of overheating, as the heatsink won't make a perfect seal on the CPU, so won't keep it as cool as it needs. I highly recommend keeping it turned off, or at least not thrashing the system, until you are able to apply some reasonable paste.

What about Cyrix (ST and TI built it, too) Cx486DX2 ? So far, at least this CPU (Cx486DX2-66 and Cx486DX2-80) have a lot of additional features, e.g. Write Back Cache (which was implemented for Intel 486DX CPUs later, with the 486DX4-100, also with the AMD 486DX-133). As far as I can see, some other CPU features found in the 5x86 are also implemented, so for socket 3/486 mainboard owners, even for the 5V only core voltage ones, this would be interesting/it would be interesting to enable these additional features. My own 486 mainboard does NOT offer any Cyrix CPU option in the BIOS, but at least two utilities support the Cx486DX also (ctchip34 and "wbon"/"wboff" found at https://github.com/karcherm/cx486wb). Unfortunately Peter Moss 5x86 tool are *not* working, also because it expects only a 5x86, regardless of the fact, that a lot of CPU registers/SMM storage addresses are the same.
Does anybody know an other Cx486DX compatible tool (and no, Cx486DRx tools are also NOT working) ?