Figure 8 To remove the card cage, brace your thumbs and pull straight back.

computer, brace your thumbs underneath and pull straight back as shown in Figure 8.

The mother board is fixed to the bottom of the cage and there may be three or four removable cards (depending on how much memory you have) arranged vertically, from back to front, as shown in Table 2.

Note that part numbers beginning with 620 refer to a complete circuit card (defined as a plug-in circuit board with all the parts on it), not an empty board, which is always referred to by another number beginning with 820. All four cards fit into tongue and socket connectors on the mother board. To remove a card, loosen the color coded bails and pull straight up. The four cards slip in and out easily, and the design makes it impossible to reinstall them backwards; although, it's very easy to get confused. Note that the CPU card faces backward, while the System I/0 card faces forward. If the CPU card offers the least bit of resistance when you try to put it in, it means you're holding it wrong. Don't force anything! Check the color codes as illustrated in Figure 9. The Memory cards and the CPU card on Lisas and Mac XL's are interchangeable. The System I/0 cards are not (The XL I/0 card will work in a Lisa but a Lisa I/0 card will not work in an XL) Physically, they fit, but electrically there are problems with disk-drive control. If you just bought a used Lisa, or if you're

Figure 9 Top view of the Usa/XL card cage. Bail colors indicate proper orientation.

restoring a Lisa and can't seem to get it going, it's important to check for the correct System I/0 card. The differences are shown in Figures 10 and 11. ROM cliff erences on the I/0 may also be present if you have upgraded you computer with a 800K floppy drive. If a screen modification kit is present in your computer the

Figure 10 The Lisa I/0 card. Note the battery pack (lower right) and the AMD 9512 coprocessor socket (upper right).