Sunday, May 21, 2017

Commodore Plus 4

At the Adelaide Retro Computing Group meeting last month I saw some amazing demos running on a Commodore Plus/4, a machine I had never seen before. Keen to learn more and since it is Commodore related, I managed to secure myself one on Ebay, a cartridge game and an sd2iec to load games and demos on it with!

It was particularly great to be able to get one still in it's original box! The history of the Plus/4 is not a good one.

Commodore came up with this machine after the Commodore 64 was released as a low end system alternative along with the Commodore 16 which is part of the same family with less memory - 16K.
It has 64K memory, but unlike the C64 has an upgraded BASIC.

But in one of those "shake your head at Commodore management" moments, the Plus/4 was not backwardly compatible with the Commodore 64 at all. It has an "all in one" TED chip handling cpu and sound duties, which is not SID chip compatible either, with a lower quality sound capability instead. What were they thinking?

The shaking of the head continues with the realisation that this computer also has new proprietary ports incompatible with any popular C64 peripherals like Cassette players, joysticks, and cartridges! The power supply port was also different! Here is a closer look at the ports:

At least the serial port (for a 1541 disk drive) and the video output port are the same as the C64, allowing me to use the same video output cable to connect the Plus/4 to my monitor.

Included with the Plus/4 I received was the manuals, which included a software manual on how to use the 4 applications built into the Plus 4 (hence the 4 part of the naming). you can see the Plus/4 is actually smaller than the C64, and in my opinion looks considerably cooler than the C64 as well.

The cursor keys are particularly different on the Plus/4, and a lot easier to use than the ones on the C64 are. I was pleased to see it powered on first time and shows the upgraded Basic v3.5:

Here is the built in word processor on the Plus/4, a truly awful application to be honest:

As mentioned I also received an SD2IEC Commodore 1541 Disk drive emulation device, specifically a Plus 4 compatible version, as the Plus/4 version needs the proprietary cassette port connector to supply power to the unit. Here is the unit:

Close up view of the SD2IEC - it has three buttons on top that light up green/red, and also serve as a reset button and previous/next disk buttons:

Here is the SD2IEC installed on my Plus/4:

I grabbed an old 4GB SD Card and downloaded the SD2IEC software from the future is 8 bit website, and put into the root folder as per the included instructions with the SD2IEC. I could then download some Plus/4 games (.D64 and .PRG) from Plus 4 World website (great site btw) and also demos from

Note that the Plus/4 can play any Commodore 16 games as well as it's own titles, but for now I am focusing on Plus/4 specific stuff. I am pleased to report that the Plus/4 SD2IEC works perfectly:

Below is the File Browser running on the Plus/4. I can use the cursor keys to navigate to the Plus4 folder where I put all my games and demos to try out:

I was particularly surprised to see some recent games made for the Plus/4, 2017 even! Here is some of the games I tried out, which worked perfectly on the SD2IEC on the Plus/4:

This game, Android 2, was written in 2014 and surprisingly fun and difficult:

The next game I tried was Adventures in Time from 2010, and I was pleasantly surprised as this game was a lot of fun - a difficult platform game:

Here is an arkanoid clone game called Arthur Noid, but unfortunately I don't have a Plus/4 joystick to play it! I have ordered a C64 joystick converter for the Plus 4 which should solve this issue once it arrives, but it did shorten my game testing since I could only play games that used the keyboard...

So, moving onto to the demoscene on the Plus/4, I had mixed success running some of the demos using the SD2IEC, much like I did on the C64 too. However I can't use the 1541UII on the Plus/4 as the cartridge port is not compatible!

Nonetheless I got to enjoy some good demos nonetheless, some of which I recognised from the Adelaide Retro Computing group meeting last month:

The effects are quite impressive indeed for such a machine, and I am glad to be able to enjoy these demos anytime!

The demoscene never cease to amaze me with what they can do with old systems in 2017!

Last but not least I also received a brand new in box cartridge game called "Jack Attack" for the Plus/4, which I wanted to try out:

The Plus/4 cartridges are a odd shape but actually look kinda cool:

Here is the game running, but unfortunately it needs a joystick so....

I thought I would cover the Commodore Plus/4 here as it was released while the Commodore 64 was on sale, and even though it failed for good reasons I already covered earlier in this post, I have enjoyed finding out more about this machine and seeing what it can do!


  1. Nice pickup there! Jack Attack has a story behind it relating to Jack Tramiel. It looks like its in top condition, so look after that one!

  2. This is a great read, thank you. I myself have just picked up the SD2IEC for our Plus 4 and was wondering if you had to connect the cassette adaptor, now I know. The 16 and Plus 4 as you said does have a nice Basic compared to the C64 but no sprites or decent sound.
    Nice to see you got the original box and it all worked, keep it as the boxed ones are staring to grab a good price now in the 2nd hand market.