Is My Jumper On The Line ?
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Number  Rev5 ?  Rev6a ? Function
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JP1     yes     yes     Connects reset timer (NE555) to main reset
JP2     yes     yes     Maps A501 at $C00000 or $80000
JP3     yes     yes     Swaps _CAS of RAM banks (of use for test purposes)
JP4     no      yes     8371  Agnus : TEST line [solder closed !!]
                        8372a Agnus : PAL/NTSC video mode select
JP5     no      yes     28MHz base clock to Agnus
JP6     no      yes     7MHz clock on pin 7 of expansion connector
JP7a    no      yes     Controls _EXRAM to Gary
JP7b    no      yes     CIA tick from VSYNC or pin 32 of A501 (default VSYNC)
JP8     no      yes     LPEN from FIRE0 or FIRE1
JP9     no      no      ??? A non-existent jumper. Future Rev. 7 ???
JP10a   no      yes     Connects AUDIN to pin 18 of serial port
JP10b   no      yes     Connects AUDOUT to pin 11 of RS232 port
JP11    no      yes     Connects CSYNC to BCSYNC or video hybrid
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NB: These are A500 jumpers only. A2000, 2500, 3000 have different jumper assignments. The 1000 *may* have similar settings but I cannot guarantee this.