The Celeron is essentially a Pentium III Coppermine series CPU with 128k of L2 cache, communicating with the chipset via a 66MHz FSB, and running at lower clock speeds. They share the same SSE instruction extensions, architecture and technology. The Celeron and Pentium III are similar enough that they are even made from the same .18 micron die using aluminum interconnects. The Celeron comes packaged in the FC-PGA Socket 370 form factor and does not work with a Slot 1 motherboard without a socket adapter.
The Celeron comes with 16k of data and 16k of instruction L1 cache. This is significantly less than the 64k of data and 64k of instruction cache that the Duron carries. L1 cache can make a huge difference to performance since it is largely responsible for keeping a CPU fed with data. The Celeron also comes with 128k of on-die, 8-way associative L2 cache, running at full-speed and connected to the processor core by a 256-bit bus. This is twice the L2 cache of the Duron. Like L1 cache, L2 cache is extremely important for keeping a processor busy.
The Celeron's main weakness is its 66MHz front side bus (FSB). At 700MHz, the Celeron uses a 10.5x bus multiplier, which is the highest multiplier we can remember for any x86 CPU. The higher the multiplier, the more you can consider the FSB as a bottleneck. The Celeron is the only current PC processor to use a bus speed less than 100MHz, and we see a significant performance hit from the lower bus speed when applications are bus intensive.
In sharp contrast, the Duron comes with a 200MHz FSB that has three times the bandwidth. You will see how things pan out in the benchmarks later in the article. Overall, the 66MHz FSB helps clearly segment the Pentium III into the high-end space and the Celeron into the value space. The problem is, the 66MHz FSB may also segment the Celeron into a value space beneath the Duron.
At 700MHz, the Celeron should consume up to ~22W of power, which is low enough to work with power supplies of 135W and less. Of course, if you match up the Celeron to a large motherboard with six PCI slots, several PCI cards, a power hungry AGP card and multiple drives, you're still going to need a power supply in the 250 to 300W power range.
From what AMD has told us, the Duron uses up to ~41W of power, which limits the Duron to 145W and larger power supplies. AMD has posted preliminary technical documents on their site giving lower power numbers. We asked AMD about these lower power numbers and they have not yet gotten back to us about what the situation is. Either way, the lower power usage of the Celeron makes it a much more versatile CPU for low-cost, low power systems.