2GB DDR or DDR2 (less for older AmigaOne and SAM boards, 1GB or so)
Console designs are not ment to be much expanded.
Not fair Vox, I easn't refering to NG PPC system.
My own MorphOS system has 1.5 GB.
But I actually gree with you that 256MB is too little.
At one time, IBM was open to tthe idea of selling the Cell to third parties (which could have brought us a board with more memory).
However, these days it would be difficult to get them to qualify that application and approve sales.