One of my project goals this weekend was to install a JiffyDOS ROM in a C64C; both of which were obtained from World of Commodore in Toronto a couple years back but had been shelved when I found the C64C's ROMs weren't socketed and I didn't have the appropriate tools or enough practice to remove them.
I assumed it was going to just require extracting the ROM chip and replacing with a socket, but after taking the shield off I realized my C64C has the 24-pin Kernal ROM, so the 28-pin JiffyDOS ROM I had wasn't going to fit:
For an added level of difficulty there was also a set of soldered tabs all around the outside that would have to be desoldered as well:
Instead of shelving it again and ordering parts, I dug around in my junk boards and found a couple network cards with ROM sockets I could salvage to help build an adapter:
The salvaged socket pins weren't long enough to perform the socket-on-socket hacks I've seen, so I decided to try using some prototype boards and pushing pin headers all the way through. My first few attempts failed; trying to put it off to the side required too much wiring (and interfered with nearby components / shield) and the next one I simply messed up the pin header alignment oh: Additionally trying to use a proto board without bus traces made it far too easy to rip off the little circular pads when putting any stress on the pin headers:
Finally after re-measuring and test fitting everything before assembling (plus using a more robust board with bus traces) the third attempt worked out much better:
( based on the multi-kernal addapter schematics from http://symlink.dk/nostalgia/c64/rom/ )
With the adapter ready to go all that was left to do was remove the lower shield and extract the Kernal ROM so I could replace it with a socket.
C64C board with Kernal ROM extracted:
Socket installed in place of the Kernal ROM -- Didn't have any 24-pin sockets, so I just clipped 4 pins from the bottom of one of the salvaged 28-pin sockets:
And after all that I was finally able to try the ROM and was happily greeted with the JiffyDOS branded startup screen
I assumed it was going to just require extracting the ROM chip and replacing with a socket, but after taking the shield off I realized my C64C has the 24-pin Kernal ROM, so the 28-pin JiffyDOS ROM I had wasn't going to fit:
For an added level of difficulty there was also a set of soldered tabs all around the outside that would have to be desoldered as well:
Instead of shelving it again and ordering parts, I dug around in my junk boards and found a couple network cards with ROM sockets I could salvage to help build an adapter:
The salvaged socket pins weren't long enough to perform the socket-on-socket hacks I've seen, so I decided to try using some prototype boards and pushing pin headers all the way through. My first few attempts failed; trying to put it off to the side required too much wiring (and interfered with nearby components / shield) and the next one I simply messed up the pin header alignment oh: Additionally trying to use a proto board without bus traces made it far too easy to rip off the little circular pads when putting any stress on the pin headers:
Finally after re-measuring and test fitting everything before assembling (plus using a more robust board with bus traces) the third attempt worked out much better:
( based on the multi-kernal addapter schematics from http://symlink.dk/nostalgia/c64/rom/ )
With the adapter ready to go all that was left to do was remove the lower shield and extract the Kernal ROM so I could replace it with a socket.
C64C board with Kernal ROM extracted:
Socket installed in place of the Kernal ROM -- Didn't have any 24-pin sockets, so I just clipped 4 pins from the bottom of one of the salvaged 28-pin sockets:
And after all that I was finally able to try the ROM and was happily greeted with the JiffyDOS branded startup screen