Searching around, it appears the number at the bottom (mostly covered up) looks more likely to be 25775 than 26050. The 25775 would indicate a plain K6.

^This. Also the fact that it was marked with paint rather than engraved (but I guess there are exceptions). Anyway, biggest difference is the VCore (3.2V for the K6 vs. 2.2V for the K6-2), so set the board for the lower value and see if it boots; if it doesn't it's probably a plain K6.

esbardu wrote on 2020-06-18, 20:02:

I have a board with a P-166 MMX where I could test it or an Asus P5A with a K6-2 533. But ... I'm afraid that testing it incorrectly might damage the boards.

The important question is not "is a K6 or a K6-2". For 233MHz processors, the important question is: Is it a 3.2V (28Watt) or a 2.2V (13.5W) CPU? There are both K6 and K6-2 233MHz processors running at 2.2V, and being a K6 or a K6-2 doesn't matter for setting up the mainboard.

There is a clue in your picture: on the ceramic case, below the heat spreader, there is a number printed in the lower left. From what I can see on the image, the only package number that matches a widely available K6 processor and is consistent with the pieces of digits on your photo is 25910. This is a 3.2V 233MHz K6 processor.

You are all amazing! Thanks!

I will test it in the P166, PCChips M520 (probably not the best brand). I had a Pentium 233 MMX on this board and I remembered that I had to chose another multiplier to get 3,5x, will need to check. I will try as soon as I can take the PC home, at home right now I have only a P3 and a K6-2 and I don't want to test it in the K6-2.

I also have an Octek RHINO 6VX .

Let's hope I don't damage anything 😀. Voltage in the two boards will be 3,3v.

It's working on a Rhino 6X, it shows as K5 233Mhz. Still need to test it.

I have directly swapped it with a Pentium 100 66x1,5. For the K6 233 1,5 multiplier works as 3,5.

I will try to update BIOS. I have too many retro projects at the same time 😀..

I'm wondering if it's miss reporting cause I thought that the K5 topped out at 133.

chrismeyer6 wrote on 2020-06-19, 13:59:

I'm wondering if it's miss reporting cause I thought that the K5 topped out at 133.

Sure, it is a K6. I guess that in terms of performance there won't be any issues but still need to test. I will also update the BIOS during the weekend.