G4: Adding memory

Hi, I've searched the older posts but I can't find a definitive answer, so I thought I'd ask around, I hope someone can help.

My colleague has an iBook G4 933Mhz with 128MB built-in and 512MB in the slot. I used the Crucial Mac Scanner to see what I could upgrade for her and the scanner insists that 640 MB RAM is the limit, yet the Apple G4 manual insists that I could add a 1GB into the slot to maximise the memory. Is it possible to do so or is 640 MB the limit?

Thanks in advance.

The 933 iBook will take a gig chip for a total of 1.12 gigs. PC2100 DDR266 200-pin SO-DIMM (PC2700 supported; however it will run at only 266 MHz).

Thanks for your help, that's good news.