The chipset selection for AMD's socket processors Athlon and Duron is quite meager, as there's currently only AMD's 750 and VIA's Apollo KT133 chipset. Only a few manufacturers - e.g. Gigabyte's GA-71XE - intend to use grandfather Irongate (AMD750). Most other board makers despise Irongate, since its restrictions to PC100 SDRAM and AGP 2x are not up-to-date anymore. VIA's KX133 chipset turned out to be unsuitable. Initially it was intended for Slot A and Socket A, but in practice the AMD CPUs only ran stable up to 800 MHz. Consequently the manufacturer dropped the KX133 for Socket A and thus you won't find any Socket A boards with the KX133.

While there is a variety of chipsets for Intel's socket processors (Pentium III and Celeron), including 440BX, 810/Whitney, 815/Solano, 820/Camino, 840/Carmel, and VIA's Apollo Pro 133 (A) as well as models from SiS and Ali, VIA's KT133 is pretty much the only alternative for Thunderbird and Duron. Two months ago most SocketA-motherboards only existed as samples, and only a few users were able to get their hands on a board back then. Meanwhile VIA is shipping a sufficient amount of KT133 chipsets to the motherboard manufacturers and customers can chose from a wider selection of boards. The current situation with practically only one chipset for Socket A motherboards, VIA's KT133, should change soon. As you can see in the following table, AMD, VIA, SiS and ALi are developing new chipsets for AMDs Socket A processors.

1 All new socket processors from AMD use the EV6 protocol. The real clock is 100 and 133 MHz, respectively. Double Data Rate offers an effective bandwidth of about twice the clock frequency (200 and 266 MHz, respectively). The Athlon and Duron CPUs currently available are specified for a 'double-pumped' system bus clock of 100 MHz.