PC133 is an open standard for SDRAM
memory, building on Intel
's PC100 standard. The architecture
of the two are as good as identical, the main difference being the differing clock speed
s: respectively 133 and 100 MHz
The PC133 standard is developed by JEDEC (www.jedec.org), helped by VIA, Micron, NEC and Samsung (among others).
Thanks to justabot for additional information.