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The competition
Those of you who haven't been paying close attention may be surprised to learn that the Sempron doesn't enter the market with a pushover for its competition. Intel's new Celeron D processor, derived from the Pentium 4 Prescott core, has quietly been earning a reputation as a decent little performer, quite the contrast from its Northwood P4-derived predecessor. Like the Prescott P4, the Celeron D is manufactured on Intel's 90nm fab process, and the D has 256K of L2 cache, twice that of the Celeron it succeeds. Intel's engineers made a bundle of tweaks to the Prescott core in order to improve clock speeds and performance, and the changes seem to have paid off for the Celeron, if not for the Pentium 4.

The Celeron D still fits into Socket 478 motherboards

The scope of Intel's microarchitectural revamp of Prescott is too vast to cover in detail here, but I'll give you some highlights. The big news is that the CPU's main pipeline has been stretched from 20 to 31 stages, allowing for higher clock speeds but potentially wrecking clock-for-clock performance. To offset the effects of this change, the Prescott contains innumerable enhancements to its branch prediction and data prefetching logic, plus lots of transistors dedicated to lowering instruction latencies, like a new integer multiplier unit. Prescott also supports a bunch of new instructions, collectively dubbed SSE3, to accelerate certain types of tasks. Intel didn't forget the cache, either, raising Prescott's L1 data cache size to 16K. (Unfortunately, the Celeron D doesn't get to partake in Prescott's improved Hyper-Threading, because Celerons don't get that feature.)

All of these modifications, combined with Intel's 865 chipset family, make the Celeron D a much more worthy competitor for the Sempron than past Celeron variants. The Celeron D would be even more worthy if it were combined with Intel's new 915G chipset and its much-improved GMA900 integrated graphics core, but that combo may not happen much until Celeron D versions arrive in LGA775 packaging. At present, the Celeron D is only available for Socket 478.

The matchup
This table should give you a quick overview of how the current lineups and Semprons and Celeron D chips compare.

ProcessorAMD SempronIntel Celeron D
Model2400+ (1.67GHz)
2500+ (1.75GHz)
2600+ (1.83GHz)
2800+ (2.0GHz)
3100+ (1.8GHz)
320 (2.4GHz)
325 (2.53GHz)
330 (2.66GHz)
335 (2.8GHz)
System bus333MHz (166MHz DDR)
or 1.6GHz HT (3100+ only)
533MHz (133MHz quad-pumped)
L1 cache128K16K + 12K uops
L2 cache256K256K
Feature size130nm90nm
I could go crazy with the specs and features in this table, but what's here should give you a rough sense of how AMD has lined up the Sempron against the Celeron. Of course, the real issues are performance and value, so let's move on to some benchmarks.