Budget CPU Upgrades: Intel's Celeron 766

What happened to the Celeron 766’s lead over the Pentium III 500E?  No longer is it a 6 or 7% lead, instead the Pentium III 500E outperforms it by over 5%.  Explaining the performance difference is simple. 

The Celeron has four things counting against it here, and they all help to nullify any performance gains its 766MHz clock would give it. 

For starters, the Celeron is still using a 66MHz memory bus.  If you remember back to our original Celeron 600 Review, we pointed out that one of the two most memory bandwidth intensive tests we ran was the Quake III Arena benchmark. 

Secondly, confounding the effect of the 66MHz memory bus is the effect of the 66MHz FSB.  We mentioned in the same review that Quake III Arena can appreciate a very high bandwidth FSB.  More recently, we pointed out similar findings in our Pentium 4 Review courtesy of the processor’s 400MHz FSB. 

The third factor working against the Celeron here is that its L2 cache has a lower hit rate than the Pentium III because of the fact that it is only 4-way associative.  The Pentium III enjoys an 8-way associative L2 cache, and the Duron/Athlon have a 16-way associative L2 cache.  The more associative a processor’s cache, the greater the hit rate. 

Finally, the Celeron only has half of the L2 cache of the Pentium III.  We can prove that this is effecting its performance by looking at the 7% performance drop from the Athlon to the Duron.  Both CPUs run at the same clock, have the same FSB/memory bus clock, the only difference is that the Athlon has a L2 cache that is 4 times larger than that of the Duron.  The Celeron’s 128KB L2 is dwarfed by the Pentium III’s 256KB L2, which also plays a role in its performance disadvantage. 

Even at 1024 x 768 x 32, a resolution that we generally declare as memory bandwidth limited by our testbed’s GeForce2 GTS graphics adapter, the Celeron comes out just slightly slower than a Pentium III 500E. 

So while the Celeron was a fairly decent upgrade for SOHO/business users that had older Pentium II/III systems, it isn’t as attractive for gamers.  But before we pass judgment let’s take a look at how the numbers shape up in other gaming benchmarks.