Final Expansion 3 for Commodore VIC-20

I did another nice retro computer DIY project recently. I bought a Final Expansion 3 DIY kit from the Retro Donald Webshop. If you remember the VIC-20 from the good old days you will know that it only had 3,5 Kbytes of RAM and you had to wait for ages to load games from a tape drive. This expansion gives your VIC-20 a lot of new features. I will tell about them later, but first the process of building the cartridge. You will have to build it yourself since it is only available as a kit. You can only choose to buy it with or without an enclosure and I chose the version without.

On the website on the shop there is a very clear manual that actually shows with pictures which components go where. Most of the stuff is pretty straight forward except for the SD cart holder that is SMD mounted. I used some flux to solder this one. In the picture you can see the finished PCB, but what you don't see is that there are some components soldered under the ICs as well. On some spots I found it quite challenging to get everything in place without putting to much force on the components. But in the end it worked out fine.

So time to put it in the VIC-20. You might have noticed the DIN plug coming from it. This is actually a serial connector that plugs into the VIC-20's serial port. The cartridge emulates a disk drive over this connector. You can load files from the SD cartridge. It is standard FAT16 formatted so you can just copy files on it from your PC. The first thing you need to load is the firmware for the expansion itself. At first I could not get it to work. I could load software I put on the SD cart, but the firmware didn't want to program. It turned out I forgot to set the dip switches right.. duhhhhh... It actually took me quite some time before I found this out. After the cartridges Eprom is programmed you can use the reset switches to reset the VIC-20 into a nice menu system. And from this
menu you can do some very nice things.

The first menu item is the most exciting one. It says RAM manager and you can add additional RAM to your VIC-20. As stated before the standard RAM amount is just 3,5 Kbyte, but you can go up to 512 Kbyte!! But there is more. You get another 512 Kbytes where you can put programs in you use often that you can then load from the menu directly. You also get a battery backupped real time clock. With the 'Basic Wedge' option you even get additional Jiffy DOS commands. If you want to learn more about this expansion you can read all about it on this URL: http://t-winkler.net/dokuwiki/doku.php?id=en:fe3:main