MHz speed of PC2-4200 RAM???

I am attempting to upgrade the RAM on my 1.67MHz Powerbook G4. It has 512MB right now and I want to get another 512 stick for a total of 1GB. My System Profiler says I have PC2-4200 RAM. I check the online RAM sites and they indicate the RAM runs at a speed of 533MHz. OK, no problem...so I thought...

I happen to look at the original box my Powerbook came in and the sticker on the box describing the machine says it contains PC2-4200 RAM running at a speed of 333MHz. Hmmmm, I thought on PC-2700 runs at that speed. Again, my system profiler says I have DDR2 SDRAM PC2-4200.

Question: Is the box wrong? Or where there two speed the RAM runs at? Are two speeds compatible? Very confused now. HELP!!!!

From what I have been told, the G4 chip does not have the capability to utilize
DDR much less DDR2 memory speeds so it treats them like SD RAM. Apparently the use of newer types of RAM was to be cost effective and probably to "hide" how dated the G4 chip was. I was disappointed when I heard this myself but after installing another Gig of RAM in my PB I am less put off b/c it does make a very noticeable difference (still would be nice to have that DDR2 speed though :headphone ) So when buying your RAM I would just buy the slowest speed to save some money since the max speed your PB will use is 333mhz, unless you planned to use those same DIMMs in another machine in the near future.