Hereunder some snapshots of Slither (other Taito's Qix hw game)... as usual, a big thanks to iq_132 (and dink for your help) !
In some cases the first time that you run Slither, the game goes in service mode and it returns a "CMOS Invalid" message (as you can see in attached snapshot). To solve the trouble it's enough:
1) press player 1 (start) to load defaults;
2) then press player 2 (start) to save.
In Slither the trackball down and right movements are half-cycle compared to up and left. So moving down or right is twice as fast as moving up or left (this issue is present in MAME too - the game would require a custom trackball code).
PS: all tech infos are courtesy of dink!