Can I upgrade the video ram of my iMac G3 400 Mhz Slot Loading Fruit 1999

Hye everybody,

I have an iMac G3 400 Mhz Slot Loading Fruit 1999 http://www.everymac.com/systems/apple/imac/specs/imac_dv_400.html .

It includes an ATI Rage 128 VR graphics card. I want to upgrade it, maar read or heard here and there that it can't be expanded, because it's just an onboard chip. Or are there other ways?

Thanks already for the tips!!

Kind regards,

Jan.