BASIC ROM & KERNAL ROM REPLACEMENT ADAPTER REV.3 , FOR COMMODORE 64

Hi, I haven't tried it for old IBM computers, so I don't know if they are compatible for old IBM computers. Thank you.

10K resistors are for pull-up A15-A14-A13 pins, and jumpers are for pull-down A15-A14-A13 pins, when you do not use resistors and jumpers A15-A14-A13 pins will float. The answer to your question depends on the 27-64 EPROM brand and model. You can try it. Thank you for asking.

I already try it, NO resistor on an AM27C64 and it works, thanxs!!!

Thanks for the info

Thank you Attila78

Hi marc-andre trudeau, This is a kernal rom and basic rom replacement adapter. It doesn't affect any game. I did not understand your problem very well. Could you please send photos and longer descriptions to my email address? c64istanbul@gmail.com Thank you.

just to make it clear i have issue with my c64 board not the adapter itself i installed this adapter on an other board same model an it is working fine this project is amazing and work really well btw you can play ultimax games without any chip in the kernal socket i think ultimax mode games use different memory mapping and do not need kernal rom at all to work properly

Jumpers are for switching between different ROMs. If you are using for only replacement you do not need to use jumpers.

Thank you for asking.

You should append kernal file to itself (8 times) to make a 64KB file (kernal+kernal+kernal+kernal+kernal+kernal+kernal+kernal). You can simpy do this with a HEX-Editor program.

Thank you for asking.

You should append kernal file to itself (8 times) to make a 64KB file (kernal+kernal+kernal+kernal+kernal+kernal+kernal+kernal). You can simpy do this with a HEX-Editor program.

Thank you for asking.

Hello Nama, I do not have a Vic-20, I did not test this PCB on a Vic-20. I can not guarantee to work on a Vic-20. I think that kernal and basic ROMs may work but character ROM may not work. If you try this PCB on a Vic-20 can you please share your experiances? PS. The EPROM files in the .zip file are only for C64, not for Vic-20, you should find and use correct files for Vic-20. Thank you for asking.

Thank you for the information. if I need to replace the Kernal ROM (still diagnosing the Vic 20), I will let you know

YES!...this worked in a VIC20 as a Kernal ROM replacement. I gather it will also work as a BASIC ROM replacement too, but not the Character ROM replacement as that uses a different ROM

Thank you Nama.

Thank you very much Mr Eddie Bannister ;)

Hi C64iSTANBUL, my pleasure! It took me a little while to work out the wiring order. Plus I was a little lazy, apologies. I would very much like to see this mod in a new version. I have another challenge for you.. Can you turn this into a PCB? https://github.com/Hartland/C64-Keyboard

I have the hardware parts for this version. https://github.com/Hartland/C64-Keyboard/blob/master/PS2/doc/Schematic_MT8808.pdf

Hello TLBradbury. Yes you are right. Thank you very much for this. If you have any problem please write. :)

Hello Douglas Kier. No, this PCB is not for C64C (short board) Kernel and Basic ROMs. Thank you for asking.

Thank you Snoop67 :)

Excuse me for such a foolish question, but where on your foto are the switches located, so you can switch between these eight kernals ?

A13, A14, A15 Headers/Jumpers are for switching between different ROMs. (If you want to use different roms then you need to prepare your binary Eprom file with your choosen ROMs)

Thank you for sharing this beautiful photo.

Does this design works for char rom too?

This PCB is designed for 8K ROMs, for 4KB C64 CHAR ROM you can use this PCB: https://www.pcbway.com/project/shareproject/CHARACTER_GEN__ROM_REPLACEMENT_ADAPTER_FOR_COMMODORE_VIC_20_and_C64.html

probably a stupid question : my char roms are on 27c64 (so 8kb ROM), does it then requires the specific adapter you designed for 4kb ROMS or this one can make the job ?

Original size of CHAR ROM is 4KB, Bigger eproms usually works. But adress pins more than needed should be connected to either (VCC) or (GND) for stablizing the unused adress pins of eprom.

Alright, makes sense. One more question: - the resistance on the char rom adapter seems to be a 10k 1/8w. Will a 10k 1/4w (same as on this design) works instead?

1/8W is smaller size than 1/4w, they both work. If you solder eprom socket before resistances you will not have problem.