My recollection of the PB1400 when it was current that it was quite a slow machine.
Additional RAM was the way to improve things (if only slightly), or a G3 CPU which were pretty expensive at the time.
Memory for the 1400 is a bit of an oddball. There is a "factory" RAM socket and a "user" RAM socket.
The "user" RAM socket can actually have 2 RAM cards fitted, but depending on the combination of modules, you'll either hit the maximum RAM or the machine won't function. (See also
http://support.apple.com/kb/TA36087?viewlocale=en_US)
The only combinationd that gave the maximum of 64MB was (with 8MB on the logic board):
8MB in the factory slot
and
two stackable 24M modules in the "user" slot
OR:
8MB in the factory slot
and
one 48MB module in the "user" slot.
The problem we continually struck was customers who had previously purchased a 32MB module wanting to go to 64MB. Sadly, they had to replace their expensive 32MB module since it wasn't usable in ANY combination to get to the magic 64MB.
NewerTech's old "
Guru v2.9" is a handy tool for determining what RAM works with many older Mac models
Also, some of the "user" modules weren't stackable.
iFixIt has
a nice guide for accessing the RAM.
