First, I will say I run a AthlonXP 2000+ as my main computer, and will be upgrading to an Athlon64 as soon as PCI-E boards are available for it.
hbdragon88 said:
A Celeron has half the L2 cache of a P4. Now, can someone explain what an "L2 cache" is and what it does?
In modern processors, the L2 cache is basically a small amount (from 128kb to 1 mb are common amounts seen in modern processors) of
really fast memory built into the processor that sits inbetween the processor's L1(an even smaller but faster bit of memory built into the CPU, where the other parts of the CPU get the info to do processing on) and the computer's RAM. The Pentium 4 Extreme Editions take this even further, and add 2mb of L3 cache to the processor. Basically, the more cache you have, the faster the processor is in most cases. Celerons are Pentium 4's with half of the cache disabled(and a slower FSB, but I will mention that later); this allows Intel save some money, by using otherwise good processors that just had some errors in the cache. AMD does the same thing with the Duron processors - a Duron is just an Athlon XP with half the cache. Adding more cache will make a processor faster.
Note that different processor designs are more dependent on cache memory than others. For example, the Northwood core Pentium 4's are very dependant on having lots of cache - a
1.6ghz Duron will beat a 2.6 Northwood Core Celeron in almost every test.
The Prescott core Celeron D chips, with twice as much L2 cache, and various enhancments, are much better performers.
Now, the Front Side Bus, or FSB for short, is basically a measure of how fast the processor talks to the memory controller chip(usually integrated into a chip that talks to a lot of things, called the Northbridge) on the motherboard. The memory controller then communicates with the RAM. A faster Front Side Bus means a faster processor, though different designs benfit more, and some don't need as fast as a connection. Common Front Side Bus speeds are 133mhz, 200mhz, 266mhz, 333mhz, 400mhz, 533mhz, and 800mhz. This covers the range from old Pentium 3s to various Durons, AthlonsXPs, Celerons, and Pentium 4s.
Just a note, the Athlon 64 processors don't have a Front Side Bus in the traditional sense - the memory controller on an Athlon 64 is built right into the processor, not into the motherboard, so the CPU can talk directly with the memory, with a hypertransport link.
This site explains it pretty well.
fret said:
Ive got a P4 2.6 running at 3.38.
Im holding of upgrading until PCIe gets a better foothold and the 1066mhz FSB arrives
Right now, the Socket 939 Athlon 64's already have an effective 2000mhz (1000mhz x DDR)connection with the memory. No need to wait for Intel to catch up.

Of course, PCIe boards for the
Athlon 64 are just starting to hit the review sites.