> Non Hi-res Powerbooks have 64MB of vram

Apart from the non-hires 17" model with 128 MiB standard VRAM (as mentioned by ausPPC) there were also 128 MiB VRAM BTO options for non-hires 15" models:

http://www.everymac.com/systems/apple/powerbook_g4/specs/powerbook_g4_1.67_15.html
http://www.everymac.com/systems/apple/powerbook_g4/specs/powerbook_g4_1.5_15_2.html

We discussed the latter one 2 years ago there:
https://morph.zone/modules/newbb_plus/viewtopic.php?topic_id=7791&forum=11&start=13 :-)