Correct VAX 8600 Maximum memory size since 64MB boards were available (Johnny Billquist)

The actual machine can have a max to 260MB of memory.
There are three different memory boards that exists for the 86x0, from a software point of view.
4MB, 16MB, and 64MB. In addition, you can mix different boards.
The rule is to put large boards first, and smaller boards later.
Even more fun is the fact that the 16MB and 64MB boards are stacked and thus take up two backplane slots in the backplane, while the 4MB board only takes up one slot.
To complete the picture, there are 8 slots in the memory backplane. You start by putting boards in slot 1, going to slot 8. The boards taking up two slots actually use slot n, while covering slot n-1. That means that the board in slot 1 does not cover up any other slot.
If you are using 16MB boards, the max memory is 68MB.
Slot 1,3,5 and 7 will have 16MB boards. And then you can place a 4MB board in slot 8.
Same story with the 64MB boards.