What cartridge is the right one for JX8P ?
Is it possible to dump the patches via sysex, and if yes, how ?

The Memory Cartridge for the JX-8P ist the MC-16, which can store 16 sounds.
A sysex dump of all the tones of the JX-8P, internal, Preset or cartdridge, is not possible at once. You have to select each single sound and record it's parameters,
but enable sysex on the JX-8P.