SC-3000 multicart homebrew

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SC-3000 multicart homebrew

Postby extra_anchovy on Tue Oct 11, 2011 2:00 pm

just came across this today

http://www.smspower.org/forums/viewtopic.php?t=13351

http://www.youtube.com/watch?v=WUY0KTbrAxg&feature=player_embedded

Image

made by a new zealand collector, maybe he's on this forum? amazing though I never though anyone would make anything like this for the SC-3000
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Re: SC-3000 multicart homebrew

Postby honestbob on Thu Jan 05, 2012 9:15 am

made by a new zealand collector, maybe he's on this forum? amazing though I never though anyone would make anything like this for the SC-3000


Well, I am now. Long time lurker, first time poster :)

Yes, I've had a lot of fun with the multicart project.

I'm finally up to doing a one-off production run if anyone is interested. You can find out more details at:

http://sc3000-multicart.com

The SC-3000 Mk II Multicart gives you instant loading of all the good SC-3000 tape games like Burglar Bill, Sorceror's Apprentice, Sir Roderick's Quest, Vortex Blaster, The House, Help, and lots more. Plus if you have your own programmer you can also add up to another 50 or so SG-1000 ROMs to the cart yourself. I don't want to get sued, and trying to ship the ROMs myself feels like waiting for a lightning bolt to strike from above. But hopefully the NZ / Aussie based authors will appreciate the dedication shown to the cause :)

Note - this is a hobby project from a long time SC-3000 fan for SC-3000 fans. The multicart is very cool and you should get one. But I think this one-off run is likely to be just that as there isn't any money in this and it is a lot of work, so get in quick if you're interested :)

I'm happy to answer any questions anyone has about the cart, or SC-3000s in general.

Cheers
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Re: SC-3000 multicart homebrew

Postby tezza on Thu Jan 05, 2012 9:33 am

Kind of reminds me of the Sorcerer cart repair I had to do. What size EPROM is it Bob?
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Re: SC-3000 multicart homebrew

Postby Carcenomy on Thu Jan 05, 2012 4:01 pm

I'm interested in one, especially since my tape drive died. How much?
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Re: SC-3000 multicart homebrew

Postby honestbob on Thu Jan 05, 2012 8:24 pm

Kind of reminds me of the Sorcerer cart repair I had to do. What size EPROM is it Bob?


Yes, I read the Sorceror cart repair post with interest. I have a lot of carts, but I've never seen an original mask ROM go bad, so that was a surprise. Maybe in a few more years. It is actually relatively cheap and simple nowadays to get your own programmer, UV eraser, and EPROMs off eBay, so that stuff has become much easier for the average person to have a go at.

The quick answer to your question is that I used 27C801 EPROMs - those are 8MBit / 1MByte in size. The longer answer goes like this.

For those of you not familiar with the SC-3000, it has a single expansion port which takes plug in games carts a bit like the Sega Master System. The SC-3000 doesn't have any bootstrap code on-board, and only 2KB of SRAM, so in general it can't do anything without a cart plugged in. The cart provides all the game code or (in the case of the Basic cart) the 'operating system' for the computer, plus additional RAM if required. The games carts usually use the on-board 2KB, the Basic carts supply up to 32KB, and the SF-7000 Super Control Station with the disk drive supplies a full 64KB of RAM.

So the SC-3000 memory architecture is very simple. The Z80 can only address 64KB of memory. The bottom 32KB is generally reserved for game ROM code (or Basic OS code), and the upper 32KB is reserved for RAM. The Multicart works by swapping out the bottom 32KB of memory with a different ROM image (all the known game ROMs are 32KB or smaller). So an 8MBit / 1MByte EPROM gives 32 slots of 32KB.

The picture extra_anchovy posted above is from the Mk I Multicart. That was my original proof of concept as I was learning. I took a Yamato game cart, desoldered the original 28 pin mask ROM (16Kb), added a 32 pin socket for the 27C801 EPROM, and used a DIP switch to control the top 5 address lines leaving the Sega to control the bottom 15 lines, giving 32 slots of 32KB. I wrote a detailed tutorial on how that works and how to do it if anyone wants to try making their own here:

http://sc3000-multicart.com/section1.htm

The DIP switch cart worked really well, but I wanted to try building a cart with a boot menu. And I really wanted to get the tape games running on the Multicart. (Cue a lot more breadboard testing). The biggest problem with tape games isn't actually the 2-5 minute load time, it is having to retry 10 times before the bl**dy thing loads correctly! And the Multicart gets around that beautifully.

You can find out more about how the Mk II Multicart works here:

http://sc3000-multicart.com/section3.htm

But in brief it works more or less the same way as the DIP switch based cart except that I use a LS373 8-bit latch to control the top 5 address lines instead of a DIP switch, and the cart has 32KB of RAM on board mapped to $8000 to $FFFF. I also added a second EPROM, so you can have a max of 64 slots (and the LS373 switches between them). There are only about 90-100 SC-3000 game ROMs around, so you can fit most of your favorites on the one cart. And you can also plug AMD 29F040 Flash EEPROMs into the lower socket instead. That halves the capacity as they are only 4MBit, but they are really convenient for quickly swapping games around.

Note - SMS Power has recently been releasing various Korean and Taiwanese dumps which were never distributed for the SC-3000 which can run on the multicart like Xevious, Yie Ar Kung Fu, Circus Charlie, Cabbage Patch Kids, Hyper Sports 2 etc.

So the SC-3000 / SG-1000 game ROMs are trivial to add to the cart, but the tape games require more work. Some are trivial, but some take 3-6 hours to convert. Basically I find the parts of the game code that call the Basic ROM tape load routines and get them to call routines to load the data from the multicart instead. You can see video footage of some of those on sc3000-multicart.com

Here's what the Mk II Multicart PCB looks like. It is plugged into an SC-3000 with the case and keyboard removed - I had to do that for the breadboard testing phase. But the PCB is designed to fit inside a standard cartridge case (with a couple of minor cuts to the case).

Image
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Re: SC-3000 multicart homebrew

Postby honestbob on Thu Jan 05, 2012 8:44 pm

Carcenomy wrote:I'm interested in one, especially since my tape drive died. How much?


That's a shame your tape deck died - a real dataset player with proper tone settings is a godsend. During my childhood we just used consumer audio tape decks, and you had to know exactly which of my two tape decks to use and exactly what volume level for each individual tape. They nearly ended up out the window a few times.

The price is $90 USD plus shipping. I'm asking for a $40 USD deposit to confirm each order. I expect the PCBs will arrive around late Feb and I will assemble them then. Futurlec did a very nice job with the prototype run, but they seem to need the odd friendly "how is it going?" email to keep things ticking over :)

It might sound a bit funny pricing in USD but all the costs are in USD, and I've had interest from some surprising places around the world, so USD it is.

You can find more details at:

http://sc3000-multicart.com/buy.htm

Have a look around the site, and just let me know if you have any questions. The cart currently has around 21 tape games on it, but it should have around 30 by the time the PCBs arrive, plus I'm still working on packing up some music demos for the music cart and a couple of other little special features.

Cheers
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Re: SC-3000 multicart homebrew

Postby tezza on Thu Jan 05, 2012 8:49 pm

Very cool Bob,

I'm always impressed with these kinds of projects. My congratulations.

We need a similar thing for Spectravideo computers (or has someone already done it?)
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Re: SC-3000 multicart homebrew

Postby Carcenomy on Thu Jan 05, 2012 10:02 pm

Interesting. I'll have a think about it and let you know :)
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Re: SC-3000 multicart homebrew

Postby tezza on Thu Jan 05, 2012 10:25 pm

These two can load cassette files as wav sound files from my PC soundcard. It ain't fast though! A plug-in, multigame cart would be just the ticket!

ImageImage

It make a great hardware project for someone. If I was retired, I'd think about having a crack myself.
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Re: SC-3000 multicart homebrew

Postby honestbob on Fri Jan 06, 2012 7:18 am

tezza wrote:We need a similar thing for Spectravideo computers (or has someone already done it?)
These two can load cassette files as wav sound files from my PC soundcard. It ain't fast though! A plug-in, multigame cart would be just the ticket!
It make a great hardware project for someone. If I was retired, I'd think about having a crack myself.


Those are very nice looking examples. I don't know much about the SpectraVideo computers - but I just spent 20 mins researching on the net.

So based on my limited knowledge, the SV-328 would probably be reasonably easy to make a multicart for. There are basically two things you need for a multicart:
1. Small games with no paging
2. Simple, predictable memory architecture (so everything you need is likely to be in the same memory location every time)

The SV-328 looks like it fits that criteria.

As I'm sure you're aware, the Z80 CPU was an 8-bit cpu, so it could only access up to 64KB of RAM. That of course was a major limit as soon as you wanted a lot of sound and graphics, so most 8 bit system that fully developed used paging to give you access to more than 64KB of RAM (eg. Sega Master System, Amstrad, later MSX etc.) So as soon as you need to support one or more different paging techniques, your multicart design gets a lot more complex and you can't use the simple TTL style design I did - you need to move to a CPLD or FPGA. For instance, there are a number of MSX conversions to the Sega Master System (like Knightmare) which run in the legacy mode used by the TMS9929A video chip which would run fine on the SC-3000 as the ports are all in the same place as the Master System. Unfortunately though the ROMs are 128KB and require their own paging system so I can't do it.

The Spectravideo 728 being MSX compatible has a different memory layout, so you'd have to think carefully about your cart design to make sure you could use it on both systems.

Unfortunately I won't be building one myself, but I'm more than happy to discuss ideas with anyone who wants to build their own. You could probably use a similar design to mine for the SV-328.

Just a word of warning though - the hardware design and testing phase is actually the smallest part of the project. Writing the cart software for the menu system and manually converting all the tape games is the time consuming bit. And it looks like a lot of the SV-328 games were on tape.

Cheers
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Re: SC-3000 multicart homebrew

Postby tezza on Fri Jan 06, 2012 7:37 am

Thanks for those thoughts Bob,

Yes, I can see such a project is not to be taken lightly. I certainly won't be doing it any time soon, but these micros seem well suited to such a thing. Much of the software can be found digitized on the web now for Spectravideo emulators such as BlueMSX so converson might not be such as issue.

Anyway, just a thought. Hopefully some hardware guru and Spectravideo nutter will read this thread and get inspired.
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SC-3000 Multicart User Manual

Postby honestbob on Thu Mar 22, 2012 3:18 pm

Hi All

Just thought I'd drop an update in here for any Sega SC-3000 enthusiasts. I've released the SC-3000 Multicart User Manual.

http://sc3000-multicart.com/downloads/S ... v1_01c.pdf

I tried to summarize and include all the interesting or relevant information that is spread around the website or in the SMS Power Dev Forums into a single document. Most of you will only need the Quickstart Guide and Care of your Multicart sections. But there is also a History section, How it Works, Programming reference, a list of all software shipped with the cart as standard, and the Credits and Acknowledgements section. I may make a few more improvements, but this is getting close to the final version.

I finally started shipping the Sega SC-3000 Multicart at the start of March. The final configuration has over 70 pieces of 1980s tape software from NZ and Australia including games, utilities, educational software, demos, and some of the more interesting type-in programs from the Sega Computer Magazines. It also has a full copy of Basic IIIB, the Music Editor plus the 10 demo Sega tunes for the Music Editor, VGM Music tracks, and a few Korean / Taiwanese ROMs for the Samsung Gam*boy and Aaronix SG-1000 II clone which have been tweaked to run on the SC-3000. And if you have an EPROM programmer you can add another 32 SC-3000 / SG-1000 ROMs of your choice yourself.

There are a couple of PCBs left, so if you're interested then pop along to http://sc3000-multicart.com and drop me a line. Funnily enough, despite being probably the third biggest SC-3000 market behind Japan and Australia, I've only had a couple of Kiwis asking for one of these. The appeal for collectors seems to be fairly global. Several Aussies as expected, but also interest from Japan, Norway, USA, Denmark, Italy, and Greece.

Cheers
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