AMD Athlon 850
Technically this slot A model is the same as this socket A (462) Athlon 850. Both have the 'Thunderbird' core with 256KB on-die full speed L2 cache. I did not benchmark the Slot A version of the 850MHz 'Thunderbird'. It should perform identical except for differences in motherboard chipsets.
The 850MHz Slot A Athlon exists in two versions. One has the Thunderbird core, the other a Pluto core. The latter is like this Athlon 500 with 512KB off-die L2 cache. The 500MHz model has L2 cache on 1/2 of the core frequency and the 850MHz model has 1/3.
Please check motherboard compatibility if you want to run 'Thunderbird' Slot A CPU's. For example the Gigabyte GA-VX7 doesn't support this CPU. If I remember correctly support for 'Thunderbird' CPU's is usually better on Irongate chipsets rather than VIA KX133 chipsets.