The heart of the Thunderbird's performance comes from its level 2 cache. As we said before, the cache runs at the full processor speed and resides on the chip's die. This high-speed cache keeps the Athlon's core well-fed with data, a task that the classic Athlon's half-speed and slower level 2 cache was unable to do well. At 1GHz+ speeds, the speed and size of level 2 cache is extremely important as the memory and FSB cannot keep up with the processors demands. The Pentium III Coppermine series has a similar 256k level 2 cache design. On the level 1 cache side, the Athlon Thunderbird is well ahead of the Pentium III. The Athlon Thunderbird packs 128k of level 1 cache, four times what the Pentium III carries.

Also keeping the Athlon Thunderbird well fed is a 100MHz FSB double-pumped to the equivalent of 200MHz. With 1.6GBps of FSB bandwidth, the Athlon FSB is not as much of a bottleneck as the Pentium III's 133MHz FSB, which only provides about 1GBps of bandwidth. The FSB is the channel between the rest of the system and the CPU, so its speed is of utmost importance. The Intel Pentium 4 will come with a 100MHz FSB quad-pumped to a 400MHz equivalent, giving a total of 3.2GBps of data FSB bandwidth, so as you can see, Intel knows that they need a fast FSB.