Is it possible for a VIC-20 ROM cart to be 32K?

Ghislain · Post by **Ghislain** » Thu Feb 12, 2009 10:12 am

Let's say I want to write a game that is going to be 32KB and occupy all of the VIC-20 memory expansion space (2000, 4000, 6000 and A000) and I want to turn it into an actual cartridge--are there any technical limitations that could prevent this?

I know there are 16K cartridges (that are located in A000 and 6000--or A000 and 4000, etc) but I've never heard of 24K cartridges or even 32K cartridges.

nbla000 · Post by **nbla000** » Thu Feb 12, 2009 10:19 am

As replied on PM you need a special hardware project for this

At the moment there is a special 16k hack project by 6502dude.

Leeeeee · Post by **Leeeeee** » Thu Feb 12, 2009 10:25 am

It can be done. The easiest way is to use four 8K ROMs and just connect the individual chip selects but it can also be done with two 16K devices or one 32K device with a little extra logic to regenerate the extra address lines.

Lee.

nbla000 · Post by **nbla000** » Thu Feb 12, 2009 11:28 am

Leeeeee wrote:It can be done. The easiest way is to use four 8K ROMs and just connect the individual chip selects but it can also be done with two 16K devices or one 32K device with a little extra logic to regenerate the extra address lines.

OK, but you need a custom PCB or may you recycle 8/16k commodore PCBs cartridges ?

6502dude · Post by **6502dude** » Thu Feb 12, 2009 11:46 am

nbla000 wrote:
Leeeeee wrote:It can be done. The easiest way is to use four 8K ROMs and just connect the individual chip selects but it can also be done with two 16K devices or one 32K device with a little extra logic to regenerate the extra address lines.
OK, but you need a custom PCB or may you recycle 8/16k commodore PCBs cartridges ?

This could be done with exisitng cart PCB (as long as it has all edgecard connector pins) + 27C256 eprom + 74LS148 (or a 74LS08 as suggested by eslapion).

It would be pretty cool to see a 32K game on Vic-20 in cart form.

Leeeeee · Post by **Leeeeee** » Thu Feb 12, 2009 12:20 pm

I recycled a C= 8K/16K cart but that's a bit more recycling than most people will do. 8^)=

Lee.

Richard James · Post by **Richard James** » Fri Feb 13, 2009 3:42 am

You can go above the 6502's memory limit by Bank switching but then your game needs to be written to cope with that.

If you really want to go silly you can have a co-processor with the ROM and RAM. There are some Nintendo titles that used this method to get 3D graphics on the SNES.

http://en.wikipedia.org/wiki/List_of_Su ... ment_chips

The question I would be asking is what sort of game requires 24K or more of data? I remember people in the MiniGame competition, talking about larger games 8K plus on 8bit systems and the fact that with modern programming techniques such as compression we can do more today with 8K or 16K than could be done in the 80's.

I'm not saying you can't make a large game. Since as you can see by the early PC games that the larger memory space allowed for more complex games like Civilisation.

With more memory you can increase
A) The amount of text in game, increases story telling
B) The amount of graphics and screens
C) The complexity of code, more complex games
D) More cutscenes and animation
C) Increase in the Music and Sound effects

There are probably many other possibilities

Ghislain · Post by **Ghislain** » Fri Feb 13, 2009 7:44 am

Richard James wrote:I'm not saying you can't make a large game. Since as you can see by the early PC games that the larger memory space allowed for more complex games like Civilisation.

With more memory you can increase
A) The amount of text in game, increases story telling
B) The amount of graphics and screens
C) The complexity of code, more complex games
D) More cutscenes and animation
C) Increase in the Music and Sound effects

There are probably many other possibilities

These are the things that I had in mind for a 32K cartridge. I could always make a 16K cartridge which would make it much easier in terms of not having to make a PCB project out of it.

With disk drives + memory expansion being very common with today's VIC-20 users, making a cartridge game for the VIC-20 nowadays seems almost like an anachronism.

Actually, a multi-loading VIC-20 disk-based game even without memory expansion could still provide all of these things (just a lot of waiting time). 170 KB per disk side is practically an infinite amount of memory for a VIC-20.

Ultimately, VIC-20 is a retro computer, and when you make a game for it, do you try to stay in the 'retro spirit' so to speak by making it a tape-based or cartridge-based game? Very few VIC-20 users actually had a disk drive back in the day. There were quite a few games that required 8K memory expansion, but none of my friends who also had VIC-20s had this. The most typical VIC-20 accessories were a single joystick and a tape drive.

The vast majority of VIC-20 games were tape games that required no expansion memory followed by those that were put out on cartridge. With a cartridge, you could reach 100% of the VIC-20 audience because they did not require anything extra on the VIC-20 except for a joystick (or a tape drive for the Scott Adams games). VIC-20 users who did not have secondary storage (tape/disk like in my situation--at least for the first couple of years) got ALL of their games on cartridge.

Right now, I'm working on my first all-ML game (Dunjon 3-D discussed in the Games forum). I could make it part-BASIC and part-ML if I wanted to (why not? RPG games use more complex mathematic functions than a typical action game) and there would be hardly any difference to the player really (Realms of Quest 2 is 75% BASIC and 25% ML). But eventually, that would mean that it would have to be a disk-based game, which goes against the VIC-20 'spirit'.

My plan was to make Realms of Quest 3 to be a disk-based multiloading game (ala Ultima IV). But if I make it a 16K (or 32K) cartridge it could be more "retro pure" because it would in theory work on any stock VIC-20 and the save game option would offer to save to disk or tape (the latter being the more traditional VIC-20 storage medium).

Ghislain · Post by **Ghislain** » Fri Feb 13, 2009 7:51 am

6502dude wrote:This could be done with exisitng cart PCB (as long as it has all edgecard connector pins) + 27C256 eprom + 74LS148 (or a 74LS08 as suggested by eslapion).

It would be pretty cool to see a 32K game on Vic-20 in cart form.

How much would it cost to produce a 32K cartridge in the way that you propose? I'm not a very good hardware guy, I'd rather focus on the software aspect of it.

Yeah, I'm really leaning towards making a 32K cart myself. I'd make a limited edition of say 10-20 copies with fancy packaging, plus a floppy disk of all my games. Of course, the game would be freely downloadable, and could be only be played on an emulator or on a real VIC-20 with Mega-Cart expansion

I've only 1-2 VIC-20 games left in me and I want to go out with a bang.

Pedro Lambrini · Post by **Pedro Lambrini** » Fri Feb 13, 2009 2:03 pm

Just to throw in my tuppence worth, I would love to see something really big and new for the Vic. While I understand the sentiment of being 'retro friendly' I do think that sometimes you can get entrenched in such thinking and miss out on great opportunities in the development of the Vic platform. You already alluded to the fact that modern programming techniques are used on and for the Vic so why not modern hardware? Over here in Blighty nobody really bought carts but everyone I knew had a 16k RAM pack...so, in my circles at least, we had a totally different demographic compared to your experience.

The fact is that you are writing a new game today and most people who would play it today have a disk drive and a RAM expansion. But you're right - everyone, then and now, has a cart slot!

Oh, and put me down for a cart if you go that route!

Ghislain · Post by **Ghislain** » Fri Feb 13, 2009 3:48 pm

Pedro Lambrini wrote:Just to throw in my tuppence worth, I would love to see something really big and new for the Vic. While I understand the sentiment of being 'retro friendly' I do think that sometimes you can get entrenched in such thinking and miss out on great opportunities in the development of the Vic platform. You already alluded to the fact that modern programming techniques are used on and for the Vic so why not modern hardware? Over here in Blighty nobody really bought carts but everyone I knew had a 16k RAM pack...so, in my circles at least, we had a totally different demographic compared to your experience.

But I want to make a cart

Well, I'll make the assembled code "cart-friendly" and it's requirement will be a Mega-Cart (at least until I can coax one of the HW technies here to help me out with making real carts once I'm finished with the programming).

Oh, and put me down for a cart if you go that route!

But... it's at best, a figment of my vaporware imagination. I've been putting off RQ3 for so long that I have to make these declarations to shame myself into getting off my butt and programming the game!!

rhurst · Post by **rhurst** » Fri Feb 13, 2009 4:34 pm

it's at best, a figment of my vaporware imagination.

If you build it, they will come.

Pedro Lambrini · Post by **Pedro Lambrini** » Fri Feb 13, 2009 5:41 pm

rhurst wrote:
it's at best, a figment of my vaporware imagination.
If you build it, they will come.

QFT

6502dude · Post by **6502dude** » Fri Feb 13, 2009 7:00 pm

Ghislain wrote:How much would it cost to produce a 32K cartridge in the way that you propose?

If you recycle an old Vic-20 cart PCB & case, this can be done for under $10. It takes about 2 hours to desolder old chip, mount socket, and hack wire it up.

Ghislain wrote:I've only 1-2 VIC-20 games left in me and I want to go out with a bang.

Which register would you use for this bang 36875, 36876, 36877, etc

ral-clan · Post by **ral-clan** » Fri Feb 13, 2009 7:02 pm

6502dude wrote:
Ghislain wrote:I've only 1-2 VIC-20 games left in me and I want to go out with a bang.
Which register would you use for this bang 36875, 36876, 36877, etc

Hehehe.