Tuesday, June 23, 2015

The Commodore 128D Journey

My main Commodore 8-bit computer since about 1990 has been a Commodore 128D. I've used it for all my programming, for my productivity, and for my gaming. I've always tried to keep it decked out. Until a few months ago, it had a 20mhz accelerator (SuperCPU) with 16mb ram, a ram drive (RAMLink) also at 16mb, network interface (64NIC), a 2mb ram expansion unit, JiffyDOS for the internal 1571, cooling fan, SuperMMU, a parallel printing interface, and several floppy drives, including a 2gb hard drive.

This all changed a month or so ago when a lightning strike ran along the network cabling in my house, affecting network-enabled electronics wherever it went. One of the stranger effects was to burn out the Character ROM IC in my C128D. Replacement was easy, but required unhooking all that stuff to replace the chip. Well, while I was in there, I decided the computer needed more decking out. In the queue are the following:

1. JiffyDOS kernal for the computer proper, so it no longer relies on the RAMLink or SuperCPU for JiffyDOS support.
2. Switchable Servant/Super 81 Option ROM
3. Internally mounted uIEC/SD, with externally accessible card slot, forward/backward switches, and...
4. A switch to disable the internal 1571 drive, switching IN the uIEC/SD instead.
5. Second 8580 SID chip with disable switch and external audio jack.

Well, that project is well underway. The JiffyDOS kernal and switch are installed, as is the option roms and their switch.

The uIEC/SD and 1571 switches are mounted, as is the uIEC with externally accessible card slot. Most people try to mount these on the front of the case, but I felt like cutting the front affect the aesthetics, so I opted for the side. The forward/back switches are on order, and will go in the spot forward of the datasette port there.

Here you can see the uIEC mount from the other side. I used some of that JB-Weld Plastic Repair Apoxy, which hardens into a plastic, to secure the unit in place. If I'm careful, I'm sure I can remove the uIEC/SD in the future if I wanted, and then screw it back into the apoxy.

Here's an overview. I've yet to start on the second SIDs -- to do that, I need to raise the SuperMMU up about half an inch, so I have some 40 pin socket on order to do that. In the meantime, I'll get started on the second SID wireing, and putting in the switch and audio jack, so it can all just be plugged in when it arrives.


  1. Hi Bo,
    very nice mods on c128, i'm interested on a dual kernal servant device manager or keydos selfmade so can i ask you how you connected and what type of ic is used?
    Thanks and best regards

    1. It is not home made -- I picked it up off eBay.