Up to 8 * 32Mbit ROMs (27C322) can be used for a maximum of 256Mbit. 27C800/27C160 can also be used depending on jumper configuration.
The size of largest ROM is selected using a pair of jumpers. The rest should be left unconnected.
Largest C ROM
Jumper set
1MiB
J5+J6
2MiB
J7+J8
4MiB
J9+J10
These jumpers seem to apply only to those two ROMs, if the ROMs are not present, simply leave both jumpers unconnected.
C1/2 ROM type
Jumper set
<4MiB
J15
4MiB
J11
C3/4 ROM type
Jumper set
<4MiB
J16
4MiB
J12
C5/6 ROM type
Jumper set
<4MiB
J17
4MiB
J13
C7/8 ROM type
Jumper set
<4MiB
J18
4MiB
J14
A NEO-273 and a LS74 are used to address C ROM. The LS74 provides the 2 most significant bits. The LS139 enables one of four pairs of C ROMs using 2 address inputs depending on which 2 jumpers are connected.
