The Elbox driver only uses one of the GPU's so it only uses 32mb as graphics memory.
I think some other PCI cards use the Voodoo's video memory as DMA buffer..such as the 100mbit network card which can only be used together with a graphicscard in the mediator.
But i would personally choose a Voodoo 3000 instead of a Voodoo 5..I switched from Voodoo 5500 to Voodoo 3000 a month ago because some games have compatibility problems with the Voodoo 5...so called big endian issues..some games show up in weid colours and such..example are Nightlong, Earth 2140
