Now I'm proposing a C64 breadbin (Longboard) JiffyDOS with "wireless" solution:
it will be sufficient to plug it on kernal ROM socket and it will work without piercing the case and WITHOUT EXTRA WIRES!

How to handle switching between kernals?
The C64 will boot-up with standard kernal (I prefer always that on standard boot-up the machine seem not modified....)
and for swapping the kernal a RESET has to be performed, Hardware or Software!

Hardware: lowering the /RES line (example: pressing the RESET button on an external card...)
Software: typing "SYS64738"(+"RETURN").

NOTE: the price includes the $ 8 that will be paid as a copyright at the conclusion of the sale.

This mod will be assembled on request.
22 (8$ royalty fees included) + eventual Paypal fees + shipping cost

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