I have a friend who owns a Dell Dimension 4300. It originally came with a Pentium 4 1.7GHz processor and after running across a few faster processors, I decided to try upgrading the CPU on the Dimension 4300. I did a bit of research and found a forum that mentioned the maximum CPU speed was a theoretical 2.0GHz for the system. So, I stuck in a 2GHz and it worked flawlessly. I also had a 2.4GHz Celeron that we yanked out of one of his newer computers and stuck that in just to see what it would do. It worked flawlessly as well.

I got to looking at the processor specs between the two and noticed that the FSB on the two processors was 400MHz. I also had a 2.60GHz with a 533MHz FSB and it did NOT work in the system. (I realize there is more to the correlation between the FSB and motherboard but I didn't feel like researching it too extensively. It's more fun to "plug it in and see what happens".)

So, I have decided that the Maximum processor speed for a Dell Dimension 4300 is going to be the highest processor with a 400MHz Front Side Bus. Like I said earlier, I used a 2.4GHz Intel Pentium 4 Celeron. BUT, I don't see why a full blown 2.4GHz Pentium 4 with a 400MHz FSB wouldn't work in the same system. I highly doubt there are any 2.6GHz processors with a 400MHz FSB, but in theory, if there is one, it will most likely work fine in the Dimension 4300.

Dimension 4300 Recap:
Maximum Known Working Upgradeable CPU: 2.4GHz Pentium 4 Celeron with 400MHz FSB

Theoretical Maximum CPU Upgrade for 4300: 2.4GHz Pentium 4 with 400MHz FSB OR Any processor with a 400MHz FSB.

I hope that answers any questions regarding the maximum cpu speed that a Dell Dimension 4300 can be upgraded to!