PC150 is strictly for overclocking. There is no official 150fsb standard. It is probably cherry picked PC133 RAM that sold for higher prices. It might be rare since only serious gamers who wanted every last ounce of performance would have paid the premium for it, for everyone else PC133 would have been good enough.

Apparently they're just 133 CL2. Oh well 😜

the PC133 standard only requires sdram to run at cl3, and thats what most common pc133 sdram rated:
hyundai -75/th
samsung -tc75
infineon -ct75
micron -75
winbond -bh75
most of these chips can also be overclocked to 133cl2 or 150cl3, if the dimm pcb is well made, however this is not guranteed.

there are also sdram chips with enhanced latency, which are factory rated at 133cl2 and 143cl3, including:
hyundai -tk
samsung -tc7c
infineon -ct7/dt7
micron -7e
winbond -bh7
of course these chips are of higher quality, and overclocking them to 150 or even 160 with cl2 is not uncommon. however you must use 16MB chips(that makes 256mb with double sided dimm, or 128mb single sided), as 32MB chips are harder to overclock.
kingmax has their own bga sdram chips rated at 150cl3, however most of them don't do well with cl2, and some can't even work stably at 133cl2. even those that do won't overclock much higher.

which chip does your corsair sdram use?

I have some different brands of pc133. the best modules I have by far are the Apacer PC133 CL2. These can do 170fsb at 2-2-2-5 timings on my Gigabyte GA6-OXET board. The Twinmos pc133 CL2 modules I have do 166fsb with timings at 2-2-2-6 which is the same as at 133fsb. The CL2 crucial pc133 ram I have does about 162 maximum at 2-2-2-5. The chips on the Apacer modules are Infineon rated at 7ns. The chips on the Twinmos modules are MTEC rated at 6ns.

Stedman

I've also have good overclocking results with Infineon chips! 153mhz CAS2 no problem 😀