Model 4 is an Athlon 'Thunderbird' - unlike models 1 and 2, it has 256KB on-die
-L2-Cache which means the L2-cache is integrated directly into the CPU-core and running at full core-clockspeed(i.e. the same speed as the CPU).
Models 1 and 2 have their L2-cache located inside the cartridge, next to the CPU - it is running at 1/2 or 1/3 of the CPU's speed(depending on the CPU's core-clockspeed).
The difference between models 1&2 is that model 2 is manufactured on a 0.18µ process - consequently, a model 2 Athlon will reach higher clockspeeds than its 0.25µ model 1 predecessor.
An Athlon 'Thunderbird'(model 4) will perform better than a model 1 or 2 because the on-die L2-cache is running much faster and has lower latencies.
You can find Datasheets and Revision-guides for the AMD Athlon here
The opinions expressed above do not represent those of Advanced Micro Devices or any of their affiliates.
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