Epson 20 - Manual (Page 118)

Installing an Option Card
The illustration below shows the nine option slots inside the
Equity 386. (Slot number 9 is occupied by the SPF card.)
SPF card
Slots 1, 2, and 9 are designed for 8-bit option cards, and slots 3
through 8 are designed for 16-bit cards. As you can see below, a
16-bit card has a second connector.
16-bit option card 8-bit option card
6-6 Installing Options