VIC-20 Super Expander and EPROM programmer

**The8-Bit Guy: Exploring the Super Expander Cartridge and EPROM Programmer for the VIC-20**

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### Introduction to the VIC-20

Hello, and welcome to this episode of *The8-Bit Guy*. In a previous episode, I discussed BASIC and its significance to machines like the VIC-20 during the 1980s. Today, I’m excited to dive deeper into the Super Expander cartridge for the VIC-20, as promised. By the end of this video, you’ll also get a glimpse of another fascinating device: an EPROM programmer that works with the VIC-20.

The VIC-20, released in 1980, was a significant player in the world of personal computing during its time. It boasted a graphics resolution of 176x184 pixels with 16 colors, although only 8 colors were typically available. For its time, this was impressive, especially compared to other affordable computers like the Apple II and Atari 400/800 series.

The sound capabilities were equally noteworthy, featuring 4 voices—three square waves and one for noise. This setup made it superior to most competing systems on the market at the time. However, the system had its weaknesses, particularly in terms of memory. The VIC-20 came with only 5K of RAM, but even less was available for user programs due to system requirements. Upon booting up, the computer informed users that they had roughly three and a half kilobytes (3.5K) of free memory.

Another limitation was its implementation of BASIC. Commodore negotiated a deal with Microsoft to include BASIC in their computers for a single fee. As a result, the VIC-20 inherited the same BASIC as the text-only Commodore PET, which lacked commands for graphics and sound. This put it at a disadvantage compared to systems like the Apple II, where users could easily write programs that utilized built-in graphical and audio features.

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### The Super Expander Cartridge

Despite these limitations, the VIC-20 had a few tricks up its sleeve, thanks to accessories like the Super Expander cartridge. Released in 1981, this cartridge was a game-changer for users looking to enhance their system’s capabilities. Let’s take a closer look at what made it special.

The Super Expander Cartridge doubled the VIC-20’s usable RAM from 3.5K to 7K by adding 3K of static RAM and a 4K ROM chip. This upgrade was particularly useful for users who wanted to write more complex programs, especially those that required additional memory for graphics or sound.

The cartridge also introduced new commands to the BASIC language, such as `GRAPHICS`, `DRAW`, `POINT`, `CIRCLE`, and `PAINT`. These commands made it easier to create visuals on the screen. Additionally, the Super Expander supported three different graphics modes, which could be initialized using BASIC commands. This was a significant improvement over the stock system, where even simple graphical programs were nearly impossible due to memory constraints.

For example, a program that created sine waves on the screen would have been impossible on the stock VIC-20 because it required too much memory. With the Super Expander, users could achieve similar results without resorting to complex POKES and PEEKS, which wasted memory and slowed down execution. The new BASIC commands made programs smaller, faster, and easier to write.

The cartridge also added sound capabilities to BASIC, allowing users to create music and sound effects using a series of `PRINT` statements. For instance, typing `V9` would set the volume to 9, while `T` and `S` controlled the tempo and speaker (voice), respectively. This feature was particularly appealing for developers looking to add audio elements to their programs.

Unfortunately, despite its potential, the Super Expander Cartridge was not widely supported by commercial software. Most games and applications were designed for systems with standard configurations, making it difficult for users to share their custom programs with others unless they also owned a Super Expander. While it addressed many of the VIC-20’s shortcomings, its lack of mainstream support ultimately limited its success.

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### The EPROM Programmer: A Glimpse into Vintage Computing

With the VIC-20 out of the way, I’d like to introduce another fascinating device that complements this retro computing journey: an EPROM programmer. While not as well-known as the Super Expander, this tool offers a unique glimpse into the world of early home computer peripherals.

This EPROM programmer, affectionately named the *PROMQUEEN*, plugs into the VIC-20’s cartridge port but isn’t as wide as standard cartridges. This means users need to be cautious when inserting it to avoid damaging the system. Unlike the Super Expander, which was advertised in Commodore Buyer’s Guides alongside similar tools for other systems, this programmer was designed for the Commodore 64 and plugged into the USER port—a detail worth noting.

The PROMQUEEN board itself is quite intriguing. It features 8K of onboard RAM but no ROM chips, meaning there’s no immediate visual or functional difference when it’s inserted into the system. To use it, you must install a software ROM chip into its socket and start the program by typing `SYS45441`. Once running, the software loads, saves, or edits HEX files and burns them onto EPROMs.

While this device is undeniably useful for its intended purpose, it has some limitations. For instance, it only supports 2K and 4K EPROMs, which limits its practicality for larger projects. However, it was likely designed with specific use cases in mind—such as programming hardware for HAM radio operators who needed to reconfigure settings on older radios.

Despite these constraints, the PROMQUEEN is a fascinating piece of history. It highlights the ingenuity of early computer enthusiasts and their willingness to push the boundaries of what home computers could do. In an era where modern technology makes such tools obsolete, devices like the PROMQUEEN remind us of the creativity and resourcefulness of retro computing.

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### Conclusion

While today’s viewers might find these devices obscure or overly technical, they played a significant role in the history of personal computing. As time goes on, documentation for such niche peripherals may become scarce, making it all the more important to preserve their stories.

I hope you enjoyed this episode and found it as fascinating as I did. If you have any thoughts or questions about the Super Expander cartridge or the PROMQUEEN EPROM programmer, feel free to reach out in the comments below. And as always, stick around for more episodes where we explore the lesser-known corners of retro computing.

Thank you for watching!

"WEBVTTKind: captionsLanguage: enHello, and welcome to this episode of The8-Bit Guy.So, in a previous episode, I talked aboutBASIC and how important it was to machineslike this during the 1980s.And I promised to do a full episode on theSuper Expander cartridge for the VIC-20.So here we are.But, I’m also going to show you at the end,a little about this EPROM programmer thatalso works on the VIC-20.This is a fascinating little cartridge, butbefore I go into the super expander, I wantto present a little refresher course on theVIC-20.It came out in 1980.It had a graphics resolution of 176x184 with16 colors, although generally only 8 of themwere available in most cases.Considering the time it came on the market,the graphics were not bad.I'd say the only half-way affordable computersthat had better graphics were the Apple IIand the Atari 400 and 800 computers.The sound wasn't bad either with 4 voices.Although 3 of them were square wave and the4th one for noise.This was still better than pretty much everyother computer or game system on the market,except for the before mentioned Atari computers.The weak point of this computer was by farthe memory.It only had 5K of RAM.But if you think that sounds bad, it's evenworse than you think.Some of that RAM is needed by the system sothere was only 3.5K available to the end user.In fact, when you boot up the computer itwill tell you that you have roughly threeand a half kilobytes free.Even as a 6 year old kid trying to createprograms in BASIC, I found myself constantlyrunning out of memory.And the other weak point of this computerwas it's implementation of BASIC.You see, Commodore negotiated a killer dealwith Microsoft.For a single fee, they were able to use MicrosoftBASIC in as many computers as they wantedto.So they just brought over the same BASIC thatthey used in the Commodore PET.The PET, however, was a text-only machine.It also had no sound synthesizer.So there was no need for any BASIC commandsto control graphics and sound, when the computerdidn’t have any.So, that meant that computers like the AppleII had an edge since people could write theirown programs in BASIC and create graphicseasily using the built in commands.Keep in mind that back in 1980, coding yourown programs in BASIC was still very mucha thing people actually did.So, it was certainly possible to get RAM expandercartridges like this one for the VIC-20.And it added some much needed RAM.However, there weren't really that many programsthat actually made use of it, since most commercialprograms tended to target the factory optionsso that the customer base would be largest.They knew if they targeted the high-end, thenthat would limit the customer base of theirproduct.And most of the good games for the machinewere distributed on ROM cartridge anyway,so there was no need to have a lot of RAMin the system for those.But, if you were writing your own programs,there was another severe limitation to graphics.If you wanted to initialize a full-screenbit-mapped graphics mode, you needed 4K ofRAM Just to hold the graphics for the screen.And as you can see, this made it more or lessimpossible for the stock machine to do full-screengraphics.So even if you were able to somehow make itfit, there’d be no room left over for yourprogram!But in 1981, Commodore released the SuperExpander Cartridge.Let's take a look inside and see what we get.It’s kind of interesting how they have theselittle metal windows.You can actually see right through to thelittle metal cover on the outside.So, let’s take a closer look at the actualboard.The first thing I noticed is that it sayscopyright 1980, even though everything I’veread said this came out in 81.And since the VIC-20 itself came out in 1980,that means this was at least in the planningstages around the same time.There are 6 static RAM chips, totaling 3Kof extra RAM, and a 4 kilobyte ROM chip.It doesn't really sound like this would addvery much capability to a computer, but itadds more than you think.For one thing, remember the VIC-20 only has3.5K of usable RAM, so this cartridge basicallydoubles that.So that's a significant improvement.Looking at the very thin manual, you’llsee some of the commands that are added toBASIC, such as graphics, draw, point, circle,paint, etc.And it gives you commands to initialize textmode and 3 different kinds of graphics modes.In the back there are some example type-inBASIC programs.So let’s stick the cartridge in the VIC-20and see what we get.The first thing you’ll notice is that thestartup screen is reporting six and a halfkilobytes of RAM.So check out this very short little exampleprogram that creates sine-waves on the screen.So, first of all, this would not be possibleon the stock machine because, like I mentioned,there isn’t enough RAM.If you had a RAM expander cartridge, thenyou could write a program in BASIC to do thisexact same thing without the new BASIC commands,but it would require about 10 times the amountof lines of BASIC code and using a lot ofPOKES and PEEKs, therefor wasting even moreof that precious memory.Not only that, it would run much slower.So by adding these commands to BASIC, it makesthe programs smaller and faster, not to mentionmuch easier to code.Here’s another very short little BASIC programthat draws 3D polygons It’s actually reallyamazing how fast these are drawn.The reason is that all of the actual drawingis being done by the machine language routinesstored in the cartridge’s ROM, rather thantrying to calculate this pixel by pixel inBASIC.So here’s another little interesting example.This program draws garfield using a bunchof circle commands.This is sort of a lost art, being able tocreate neat pictures like this out of a stringof commands, it’s kind of fun to watch asthe picture comes alive with each new strokeof the pen, so to speak.And here’s one last little program I’llshow you, which creates some very strangeart.It has several different screens it goes through.Whoever wrote this seems to like eyeballs.Besides graphics, it adds sound commands toBASIC, but in a really clever way.You can create sounds with the print command.Once you’ve typed the first quotation mark,you press control and the left arrow likethis, which creates a little reverse F.This tells it you want to print sound insteadof text.So you have to start off by setting some parameters,such as V9, which sets the volume to 9, thenT for tempo, then S for speaker, which isanother way of saying voice..In this case I’ll use voice 1.Then I’ll use octave 2, and then some notes.”Now lets see what happens.OK, so if I wanted to make that a full scale,I could add A and B, then I’ll need to changeto octave 3 for the next C. OK, to betterdemonstrate, I actually wrote a small musicalsample, which is part of the music for myCommodore 64 game I’m working on.You can see it is just a bunch of print statements.So, you can see how easy this makes it toadd sound and music to your own programs.All right, So what do I think of the super-expandercartridge?Well, I think it’s a really great cartridge,but the problem is it shouldn’t have beennecessary.They really should have built everything inthis cartridge into the logic board from thevery beginning.Because it was not part of the standard system,there was virtually no commercial softwarethat supported it.And even if you wrote your own games usingthis cartridge, those games still wouldn’twork on your buddy’s computer down the streetunless he too had a copy of the super expandercartridge.So, while it did fix many of the shortcomingswith the VIC-20, it was still, in my opinionkind of a failure.OK, so the next thing I wanted since I havemy VIC-20 out is this EPROM programmer thatI was sent.I really wanted to show it to you, but therereally wasn’t enough information to reallymake a whole video about it.So, let me just give you a little overviewof this thing.So let’s take a look at this eprom programmerwhich was donated to me by Aaron Katz.This plugs into the VIC-20’s cartridge port,but one thing you might notice is that whileit has the same edge connector as a cartridge,it isn’t as wide.So you have to be really careful insertingit in since it doesn’t automatically lineup.Take a look at the Commodore Buyer’s Guide.This is from a few years after the VIC-20was discontinued, but you’ll noticed theydo advertise an EPROM programmer for the Commodore64, but it plugs into the USER port, not thecartridge port.So that’s interesting and it ends up havingsome advantages I hadn’t thought of, whichI’ll show you here in a minute.Looking at the board, I noticed that its calledthe PROMQUEEN.Quite a clever name.I also noticed that, if my math is right,it has 8K of onboard RAM, but no ROM chipsto be seen.So when you power on your VIC-20 with thisthing in the computer, there’s actuallynothing noticeably different.Not even any increase in RAM.So you might think the software would comeseparately on a disk or maybe a cassette,right?Nope.Instead, they actually give you a ROM chipof the software, which you have to place inthis socket.Now this socket is actually mapped directlyto the VIC-20’s memory map, but it is ata non-standard location so it can not auto-startlike a game cartridge.So you can actually stick the chip in whilethe computer is on, then type SYS45441 tostart the software.Once the sofware is started you can removethe chip.This is because it copies itself over to RAMas soon as you start the program.This software will let you load, save, oredit HEX files and then, obviously, burn themto an EPROM.Well, since it only handles 2K and 4K EPROMs,it isn’t all that useful to me.If it could do at least 8K EPROMS I couldprobably find some interesting uses for itaround the house.But, it’s still a pretty neat little devicefrom the time period.I think it was targeted a lot at HAM radiooperators who needed to reprogram EPROMs inthose old HAM radios to change various channelsand settings and things like that.Of course, none of that is necessary on themodern HAM radios because it can all be donein software.Well, I hope the episode wasn’t too mundanefor you.I really have a lot of little peripheralslike this that I want to show off that probablya lot of people have never heard of before.You know, in another 20 or 30 years they mayfall into obscurity to the point there’sno documentation on them.So, I think it’s kind of important to talkabout them and see what place they held inhistory.So, let me know what you thought, and stickaround for more content.\n"