The Pentium III 1GHz sports 256KB of on-die L2 Advanced Transfer Cache (ATC) running at the processor's full core speed. With a 256-bit bus, the L2 cache attains 16GB/second of memory bandwidth at 1GHz. You can read more details of the ATC system in our Intel Pentium III 500E CPU and 550E FC-PGA CPU Review here. In the meantime, here are the specs:

Pentium III Processor Core 256KB Advanced Transfer Cache On-Die (ATC)

• 8-way set associative, 1024 sets
• 32 byte line (32 bytes data, 4 bytes ECC) every 2 clocks, equals 16GB/sec throughput at 1GHz
• 36-bit physical address space
• 4 x reduction in latency versus Katmai PIII L2
• Cache bus speed fully scalable with core frequency
• 288-bit transfer width (256 data, 32 ECC)
• 2 cycle back to back throughput

Advanced System Buffering (ASB)

• 6 Fill Buffers (increased from 4) offer increase of 50% in concurrent non-blocking data cache operations.
• 8 Bus Queue Entries (increased from 4) allow more outstanding memory/bus operations.
• 4 Writeback Buffers (increased from 1) offer reduced blocking during cache replacement operations along with faster deallocation time for fill buffers.

And those are the details for what is essentially the original Coppermine CPU running at 1GHz. But we know what you really want is the benchmarks...