Not quite as much as we'd hoped: just the 150MHz needed to reach 1GHz.

Despite the insanely high clock speed, AMD's latest offering still lacks the on-die cache we've been so patiently awaiting. While, clock for clock, the Athlon is ahead of Intel's Coppermine, in cache intensive applications AMD's 1GHz part will take a performance hit.

As you may have guessed, the lack of an on-die cache means we're not dealing with the upcoming "Thunderbird" core which was originally speculated to be introduced around this time. Instead, the new Athlon is equipped with the K75 core that was introduced with the 700MHz part.

With a move to the K75 core, AMD was able to shrink their die from .25 to .18u. At 102mm˛, the K75 requires less voltage and puts out significantly less heat than the previous K7. AMD has kept very tight-lipped regarding the wattage their Athlon processors consume, but we should be able to count on any system shipping with an Athlon conforming to the "Recommended Power Supply" list found here to maintain complete stability.

Up until the 700MHz Athlon was released, AMD employed a 1/2-cache divider similar to Intel's Katmai Pentium IIIs. Once 700MHz was reached, it became necessary to change the divider to 2/5 in order to keep the SRAM cache operating within its manufacturing tolerance (which equated to 340MHz on our 850MHz Athlon). At 1,000 MHz however, this divider would result in an off-die L2 cache running at 400MHz, apparently over and above the speed at which AMD would be able to get reliable yields.

A 1/3 cache divider, running at 333MHz (that's right folks, running 7MHz slower than the 850). We had hoped that the first GHz Athlon would be introduced sporting the "Thunderbird" core with a full speed on-die L2 cache (which has already been demonstrated). However, the race to break the GHz barrier may have rushed this processor to market.

The road map below shows that the transition from slot A to socket A will take place in the middle of this year. Then and only then, will the full-speed on-die cache be implemented by AMD in the form of the "Thunderbird" and "Spitfire" (aimed at the value sector) cores. Larger on-die cache on Athlons ("Mustang") will also be an important factor when going head to head with Intel's Willamette towards the year's end.