Samsung Alpha 21264A (EV67) and Alpha 21264B (EV68) processors
Introduction: 1999 (Alpha 21264A) and 2000 (Alpha 21264B)
21264A (EV67) entered the market in the end of 1999. Was produced by Samsung using a 0.25µ CMOS process, posessed a die size of 210mm² and required a lower power supply of 2.0V. No significant architectural differences if compared to EV6. 21264A (EV67) core frequencies ranged from 600MHz to 833MHz (TDP approx. from 70W to 100W) which allowed the Alpha architecture to bring back the leadership on integer tasks, lost not so much time ago to Intel Pentium III (Coppermine) and AMD Athlon (K7).
The first samples of 21264B (EV68C) were delivered in the beginning of 2000. This processor was produced by IBM using a 0.18µ CMOS process of its own involving copper conductors. Despite absence of any architectural differences still, the promising technology allowed to rise core frequencies right up to 1250MHz. In 2001, Samsung became able to manufacture 21264B (EV68A) in quantity using a 0.18µ CMOS process of its own, but involving aluminium conductors. If compared to EV67, the die size was reduced by over than one third (to 125mm²), also the voltage did decrease (to 1.7V). 21264B (EV68A) core frequencies ranged between 750MHz and 940MHz (TDP approx. from 60W to 75W). It was declared in September of 1998 that EV68 by Samsung would be implemented in an innovative 0.18µ FD-SOI (Fully Depleted Silicon-On-Insulator) process involving copper conductors, so it should be able to reach 1.5GHz and even more. Unfortunately, it didn't happen.
Different sources mention 21264C and 21264D, code-named as EV68CB and EV68DC respectively, manufactured by IBM using the same technology as EV68C and running within the same frequency range, so they could be considered as minor modifications. The only noticeable difference was a new form-factor, pinless LGA-675 (Land Grid Array) instead of PGA-587. Apparently, these processors were installed in Compaq servers only.
Source: www.alasir.com