Taito Polaris 27128 EPROM Hack
by Mark Spaeth
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Polaris uses 7 2716's, 5 in sockets, and 2 on a daughterboard, with one rom
enabled by a fly-wire going to the pin 7 on a 7442 BCD decoder.

The correct rom mapping is:
PS-01: 0000-07ff
PS-02: 0800-0fff
PS-03: 1000-17ff
PS-04: 1800-1fff
PS-05: 4000-47ff
PS-10: 4800-4fff    <=- on daughterboard
PS-26: 5000-57ff    <=- on daughterboard, with fly-wire

The schematics on Spies are not correct for the 2-pcb set, so we'll have
to hack a little to figure things out :)

The 4 inputs to the 7442 are:
D: /enable (?)
C: A14
B: A12
A: A11

The rom enables on the 2716s (/OE, /CE -- 18, 20) are tied together, so the 'D' 
input on the 7442 should be enough to enable the 27128, with A14,12,11 tied to
A13,12,11.

Thus, the complete hack is:

1. Bend up pins 1,2,20,22,23,26,27,28 on a 28 pin socket, and drop it into any 
   of the existing rom sockets

2. Tie 1,27,28 to VCC

3. Tie 20,22 to IC72:12 (enable)

4. Tie 23 to IC72:15 (A11)

5. Tie 2 to IC72:14 (A12)

6. Tie 26 to IC72:13 (A14)

...and it should work!