YES the onboard cache is disabled. Think of buying a Porsche because you want to drive really fast on the Autobahn, but than removing half of the sparkplugs. It's the same chip, just severely crippled and lacking 40%+ of the performance.
Save heating costs on your home, overclock your PC!!!
The last guy was wrong. The difference in performance is around 30%-50%. Most of this difference is due to the very slow memory transfer rate caused by the 100MHz bus. The rest is caused by the cache being slowed from 0 cycles (instant) to 1 cycle. A PIII 1000EB is faster than a Celeron 1.3GHz. I had a Celeron pushed all the way up to 1480MHz and it couldn't get ahead of my PIII 1000EB on the same system.
If you think you'll save money with the Celeron 1.3, you won't really, it cost almost as much as a PIII 1GHz. If you really want to save money AND get decent performance by using a Celeron, I suggest getting the Tualatin 1.0GHz version and overclocking it to 1.33GHz. At least that gives it the memory bandwidth of the PIII. And the 1GHz Tualatin Celeron is around $50.
<font color=blue>You're posting in a forum with class. It may be third class, but it's still class!</font color=blue>