Z97M Anniversity OC limit?

The Celeron 300a (Mendocino) was a Slot 1 CPU so it was a cut down version of the Pentium II. The whole slotted CPU design came about because of cache shortages so CPU manufacturers got around it by using a daughter board system with different cache ICs that could be found more easily. Once the shortages were over we saw the birth of the first Pentium 3 (Coppermine) Socket 370 CPUs. 

I used a high end server board (I forget the model now) for my 300a which had jumpers that allowed me to manually set the BCLK all the way up to 166mhz via jumpers on the board, that combined with some insane voltage mods and cooling got my 700mhz result that stood as a record briefly among my co workers at the time. You have to bare in mind this was some years later and we didn't care if we burned up the CPUs we were playing with  My cooling solution involved coating the entire motherboard and CPU+heatsink in thick non conductive grease and encasing the entire CPU in ice except for it's slot edge connector. I then submerged the entire motherboard in an ice-water filled bucket turned it on and waited for the sparks to fly. They didn't and I briefly got to see the glorious 700mhz figure on the post screen before the water began to boil and I shut it off   We must have fried a dozen or so old boards experimenting with various overclocks and cooling methods in those days. If I had known about LN2 back then...... Interestingly HWbot only has 2 Celeron 300a entries of 700mhz and over, that was one hell of a CPU, I wish I still had it. I need to correct my last post, I ran mine at 533mhz 24/7 not 633.... typo.... Most hit 450mhz easily even on stock cooling. You also have to bare in mind we didn't have access to advanced coolers back then, it was either stock, slightly better than stock or completely home brew  I think I was in my late teens/early 20s back then and a little too careless with my kit now that I look back on it 

I was so frustrated when one of my co workers managed 733mhz on his AMD K6 III 550, we were trying to see if any of us could get close to the 1ghz of the as yet unavailable at the time Pentium III coppermine 1ghz CPU that had just been released. He ended up winning the competition and a month of Friday afternoons off. Our boss was a blast and always came up with fun/crazy team competitions and team building exercises. I still maintain it wasn't fair, 550mhz to 733mhz was nothing compared to 300 to 700mhz 

This little guy only manages about 4.4ghz before voltages and temps get out of hand, even using an AIO Corsair H105. My Z170 Pro4s is about the equivalent to your Z97 Anniversary but from the skylake lineup. I have added beefier VRM cooling to it but it hasn't opened any doors regarding overclocking unfortunately. It does look better tho....