HELP Memory upgrade problem

Have an old NEC Ready 9730/9740 PC

According to the manual the system board supports up to 256mb ram.Also says system supports 16mb by 32bit simm stick (64mb module)
I have just bought 4 64mb modules and the pc will not see 256 have swapped memory chips around installed only two at a time etc etc.
When all 4 are installed pc only see’s 64mb when only 2 are installed pc sees only 32mb.
I dont think the memory is faulty but havent ruled out that possibility yet but would have thought it wouldnt boot at all if any of the chips was fauty when i place them in pairs.
Is it possible that the manual is incorrect?