Apple-1-HW/RC6502-Apple-1-Replica
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RC6502 ROM/README.md
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@ -10,7 +10,7 @@ The RC6502 computer makes the same changes to the hardware dealing with ROM as w
The implementation of the ROM module answers to addresses from $E000 to $FFFF, in other words the last 8KB of the 6502s 64KB total addressable memory space. The onboard socket takes an EPROM/EEPROM with sizes from 64Kb (27C64/28C64) to 256Kb (27C256/28C256), the latter size giving you the option of using up to four switchable combinations (using A13/14 jumpers). When using the smaller size, these two jumpers should be left unjumpered as the corresponding address pins whould be designated NC (No Connect) on the chips themselves! The implementation of the ROM module answers to addresses from $E000 to $FFFF, in other words the last 8KB of the 6502s 64KB total addressable memory space. The onboard socket takes an EPROM/EEPROM with sizes from 64Kb (27C64/28C64) to 256Kb (27C256/28C256), the latter size giving you the option of using up to four switchable combinations (using A13/14 jumpers). When using the smaller size, these two jumpers should be left unjumpered as the corresponding address pins whould be designated NC (No Connect) on the chips themselves!
**NB!** Note that the redesigned RAM module now supports ROM chips on the same card, so if you do not intend to use the optional paging feature you may want to consider using the new RAM module instead (normally you'd get 5-10 per order anyway)! **NB!** Note that the redesigned RAM module now supports ROM chips on the same card, so if you do not intend to use the optional paging feature you may want to consider using the new RAM module instead (normally you'd get 5-10 per order anyway)! Note that this might come at an increased cost since the new RAM module requires more ICs to function, but these should be cheap as chips (the potato kind) anyway!
## Optional feature ## Optional feature
The board enables the use of backplane pin number 39 for paging purposes, this in essence means the ability to shut of the ROM module using appropriate hardware for controlling this pin. This would enable the computer to regain this section of memory space for other purposes afterwards, possibly by switching it out for more RAM... In most cases this will not be needed, so instead I encourage you to solder a hard links between pads 2 and 3 on JP5 - U2 can also be left off the board. The board enables the use of backplane pin number 39 for paging purposes, this in essence means the ability to shut of the ROM module using appropriate hardware for controlling this pin. This would enable the computer to regain this section of memory space for other purposes afterwards, possibly by switching it out for more RAM... In most cases this will not be needed, so instead I encourage you to solder a hard links between pads 2 and 3 on JP5 - U2 can also be left off the board.