Net-N-Dude Glacier 4500C Arctic Cap Celeron Cooler

The old 266 can generally make it up to 400MHz without a hitch, 448MHz (112MHz x 4.0) is a possibility however it is reserved for the higher yield processors if you can still find them. Pushing the Celeron 300 to its highest realistic overclockable potential, 450MHz, is a bit more difficult than overclocking the 266. Your chances at coming across a 300 that can make it up to 450MHz reliably are slim in comparison to finding a 266 that can hit 400MHz. A 266 will hit 400MHz with decent cooling, a 3+ fan super cooler is not necessary to get the majority of processors up that high (keep in mind that not all processors are created equally, and some may not even pass 266MHz).

The OEM Celeron 300A is a unique find, since the latest batch of OEM processors don't seem to be as friendly at 450MHz as the original 300A's were. Here's where the benefits of a superior cooler may come into play. Most 300As have a core capable of hitting between the 400 - 450MHz mark, however once you begin to push the limits of your CPU and attempt to actually overclock to the 450MHz mark the processor will begin to heat up dramatically. This causes instability as well as irreversible physical damage to the die of the CPU. The question of whether or not your OEM 300A will make it up to 450MHz or not depends entirely upon the quality of the die and the manufacturing of the CPU itself, so it is pretty much a toss up.

The retail 300A processors have a considerably higher success rate at 450MHz, however they too are disappearing off the face of the overclockers' market. Most retail 300A's work fine with their standard heatsink/fan combos and don't usually require the addition of any third party cooling products.

Unfortunately, the 333A is apparently much like a 300A, in the sense that it requires a bit of work to get it up to the 450MHz mark. At the same time, 450MHz isn't physically possible for the 333A due to its 5.0x clock multiplier, leaving the only 100MHz FSB option as 500MHz. On most 333's, 500MHz is a stretch since you begin to approach the theoretical limit of the Celeron A core as it stands (500 - 550MHz is the theoretical limit using the current manufacturing process). Added cooling usually doesn't help it 500MHz for 333A processors, however there have been rare success stories of 333A owners running perfectly at 500MHz. The odds are against you with a 333A at 500MHz, regardless of what type of conventional cooling you happen to be using.