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 in 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 and the L2 bus is four times wider than the Duron's 64-bit L2 cache bus. 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 766MHz, the Celeron uses an 11.5x bus multiplier, which, to our knowledge, is the highest x86 CPU multiplier of all time. The higher the multiplier, the more the FSB becomes a bottleneck, since the processor cannot get information from memory as quickly. 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. This situation is further aggravated by the Celeron only having 128k of L2 cache, as opposed to the Pentium III's 256k.
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, and we believe these differences are mostly due to the difference in FSB speed. The 66MHz FSB clearly keeps the Celeron from competing with the Pentium III, placing it firmly in the value space. The problem for Intel is that the 66MHz FSB hobbles the Celeron, keeping its performance well under that of the Duron.
Intel knows this, and while the performance shortfall hurts Intel in the current component market, it does not hurt them as much in the OEM market. In January, there will be another round of OEM deals, and as we said in our recent roadmaps, Intel will release Celerons with a 100MHz FSB, no doubt timed to win OEM designs in January with their boosted performance.
At 766MHz, the Celeron still just sips on power, and will work with power supplies of 135W and even 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 range.
From what AMD has told us, the Duron uses up to ~41W of power, which is why they recommend 145W and larger power supplies, with the same caveat about larger systems. AMD's upcoming Mustang CPU will have a mobile variant that will use much less power.
For a more complete look at the Celeron architecture, please check out our Intel Celeron 600MHz Review, where we take a closer look at the Celeron's architecture.