Intel Coppermine Socket 370 microprocessor

8 months after introduction of Katmai core, Intel released first processors with Coppermine core - new Pentium III core based on 0.18 micron technology. Better manufacturing technology resulted in smaller die size of the CPU, and with smaller die size it became economically feasible to incorporate 256 KB level 2 cache on the die. Although the size of this L2 cache was two times smaller than the size of L2 cache in previous generations of Pentium II and Pentium III microprocessors, the advantage of the cache was in its speed as the cache was running at processor frequency, while back-side cache of older Pentium processors was running at half of the processor frequency. The new L2 cache utilized 256-bit data path to the cache, which was 4 times wider than on Katmai processors. The cache had lower latency and included "Advanced System Buffering" feature. Intel referred to this cache as "Advanced Transfer Cache". Increased speed and other improvements in cache design compensated for smaller cache size, and overall performance of Coppermine processors with Advanced Transfer Cache was on average 10% faster than performance of Katmai CPUs with bigger but slower back-side L2 cache.

By integrating L2 cache on a die, Intel eliminated external cache chips - the main reason why the bulky slot-type cartridge was required in older Pentium II/III CPUs. With the new Coppermine core it became possible to put the processor on smaller and cheaper PGA-type plastic package. Unlike older socket 370 Celerons and Pentiums in plastic PGA packages, new Pentium III package didn't have integrated heatsink. On one hand this was an advantage as it allowed more efficient cooling of the core. On the other hand CPU installation procedure became more delicate as it was possible to accidentally damage the core during heatsink installation. The new package had 370 pins and required socket 370, though this socket 370 was not compatible with original socket 370 used by Mendocino Celeron processors. For new Pentium III processors Intel revised electrical specifications of socket 370, as a consequence new Pentium III processors would fit into older motherboards, but would not work there.

Coppermine processors had lower power requirements than Katmai processors due to lower core voltage - 1.5 - 1.75 V as opposed to 2.0V for Katmai core.

To compare different versions of Pentium III CPUs please see Intel desktop Pentium III CPU chart.