Now you have half of the story... here's the rest.
Internal multipliers on the Intel CPUs are fixed.
The 600E chip, for instance has a 6x multiplier, and expects to see a system clock providing the FSB (and CPU) with a 100MHz frequency .... 6 times 100 = 600MHz
The 600EB chip has a fixed internal multiplier of 4.5, expects to see 133MHz on the system, allowing the processor to acheive it's nominal 4.5 time 133 = 600MHz
The E series was made to allow owners of BX boards to upgrade to PIII. It was not a coppermine originally, but all PIII processors over 600MHz (I think) have the 64bit datapath to the on board L2 cache, which is the fundamental difference from earlier PIII chips.
Be aware, however, that older BX boards have older BIOS, so it is sometimes necessary to flash the BIOS to a new version (see your mobo manufacturer's website for that).
Also, if you own a BX board, and attempt to use an EB (133MHz) chip, you will have to overclock to 133MHz FSB to get the chip up to it's rated speed ! Your memory and graphics card might not cut it at the overclocked settings. Many BX owners have made the unfortunate error of buying an EB chip. See Tom's complete overview and explanation @
....tomshardware.com/mainboard/00q1/000308/fsb-133-2-01.html
The nice thing about the BX chipset is that is DOES tolerate overclocking to higher FSB speeds. Mine is happilly feeding my 700E chip 140MHz, forcing the CPU to post a cool 980MHz.
There you have it.
Remember...
AMD stands for Another Meltdown Disaster (toast-wise)