PowerBook 3400 & G3 Modems: Are They Flash Upgradeable?

Are the PowerBook 3400 series and the PowerBook G3 (M3553) internal modems flash ROM upgradeable?
The PowerBook 3400 series and the PowerBook G3 both have 33.6 internal modems. These modems are not upgradeable to a faster speed.
Published Date: Feb 18, 2012