Before concluding that the Router "A" 3640 is faulty I thought I will post this in the forum.
We have two 3640 Routers "A" and "B".
Router "B" has 2 x 32 MB memory and 2 x 16 MB memory = 96 MB.
If we move all these memory cards to Router "A" then Router "A" only sees the memory installed in Banks 0 and 1, but does not see the memory installed in banks 2 and 3.
So if I have 32,32 in banks 0 and 1 and 16,16 in banks 2 and 3, then router "A" shows 64 MB only. But if I have 16,16 in banks 0 and 1 and 32,32 in banks 2 and 3, then router "A" shows 32 MB.
Router "B" shows the full 32,32,16,16 = 96 MB. So all the 4 memory are good.
It appears that for some reason banks 2 and 3 slots are faulty in Router "A".
IOS versions, H?W revision numbers are exactly the same fro both 3640 routers "A" and "B".