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Zerosquare

Jagtopus v2 interest check

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A few years ago, I started working on the next version of the programmable Jagtopus cartridge. I wanted to add support for larger Flash memories (8 MB and up) and larger save EEPROMs (say, 32 kB), and maybe a few other extras. I designed a schematic, started routing the PCB, then I got distracted by other projects and never finished it. To be honest, the lack of demand for bigger carts was also a factor.

 

Recently, there have been talks of projects needing more than 4 MB of ROM. Yeah, I know what's you're thinking: what's the point of such a project, now that the JagGD exists? Well:

- not everybody has one

- some people prefer physical cartridges over SD cards or digital downloads, either because they like collecting physical stuff, or because they feel part of the nostalgia is using the console like it was used back in the day.

 

Here's where I need your feedback. As homebrew developers:

- what do you think of the idea?

- would such a product be useful to you, and if so, how would you use it?

- besides the larger memories, are there any extra features you'd find useful? (please note that unlike the Skunkboard and the JagSD, this would be a cost-optimized design for releasing games, not a development tool or a multicart. So don't expect anything too fancy ;)).

 

At the moment, this is just a potential interest check. No promises, no preorder lists, nothing has been decided yet :)

 

Edited by Zerosquare
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Definitely interested! I somehow didn't realize that Jagtopus v1 actually went into production a number of years back, so I missed it first time around. A cost-optimized solution for 8MB+ would be great. Bigger is better, of course, but I assume there would be some bankswitching etc. needed to get past the 6MB ROM space?

 

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Yes, bankswitching is needed to make it work. The simplest scheme would be this:

- $800000 ~ $BFFFFF: fixed area, always maps to the first 4 MB of the ROM

- $C00000 ~ $DFFFFF: configurable area, can be switched to any bank

More elaborate banking schemes are possible, but I don't yet know how they would impact the price (depends whether a small CPLD is significantly more expensive than discrete logic).

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There is definitely going to be a demand for larger cart sizes soon, you can count on it. And like you said, larger carts will be necessary once the games to take advantage of them come along, as not everyone is going to have a GD. As far as extra features go for a project like this, I'd say don't worry about them, they would probably just add to the cost of development with minimal usage at best.

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2 hours ago, Zerosquare said:

Yes, bankswitching is needed to make it work. The simplest scheme would be this:

- $800000 ~ $BFFFFF: fixed area, always maps to the first 4 MB of the ROM

- $C00000 ~ $DFFFFF: configurable area, can be switched to any bank

I have used bankswitching on different platforms by the past, but could you elaborate on how the bankswitching could be done on the Jaguar?

What register(s) need to be manipulated by example?

Many thanks for your input.

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Interested. I too didn't know about v1 so would like to opt in this time around :)

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May be interested if I ever get done building skunks and have time to work on my actual game code project again.

 

What sort of price are you targeting, and how would it be programmed? When I was pricing out the new Skunkboard components, I found the most expensive part was getting decent quality PCBs with real gold fingers 😞

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7 hours ago, dilinger said:

I have used bankswitching on different platforms by the past, but could you elaborate on how the bankswitching could be done on the Jaguar?

What register(s) need to be manipulated by example?

Besides the $800000 ~ $DFFFFF cartridge ROM area, the Jaguar has a few other areas that are accessible over the cartridge bus:

image.thumb.png.e2e356eaedd37b2c32239c19dd99e5d3.png

GPIO0 & GPIO1 are not available (they control the cartridge's EEPROM), but other should be usable to put the banking register(s) in.

The register(s) bit layout has not been decided yet, it will depend on the banking scheme.

 

6 hours ago, Saturn said:

Interested. I too didn't know about v1 so would like to opt in this time around :)

Yeah, I should have put a link to the Jagtopus v1 thread for info:

 

5 hours ago, cubanismo said:

What sort of price are you targeting

I have not set a target price yet. I prefer to evaluate the various options first.

 

5 hours ago, cubanismo said:

I found the most expensive part was getting decent quality PCBs with real gold fingers 😞

Yeah, "real" gold (as opposed to flash gold, which is just a very thin layer) is expensive :(

 

5 hours ago, cubanismo said:

how would it be programmed?

There are two existing options for programming Jagtopus PCBs:

- uploading the code from a PC thru the 2nd joystick connector. But since the throughput is limited, it would probably be too cumbersome for 8+MB games.

- using an external programmer designed by SCPCD. It's a much better option for mass production, since it can program 4 PCBs in parallel. But the hardware is not cheap (the design hasn't been optimized for cost, and the 4 cartridge connectors alone are pricy).

 

Using the JagCD is a possibility, but my religion forbids me from even looking at that thing :D

(seriously though, anyone wishing to try it is welcome, but don't expect me to.)

 

Using a JTAG programmer may be an option, but that requires a CPLD with connections to the entire address and data buses, which may raise the price.

 

One possibility I've considered is a modified Jaguar: the ROM image would be stored on a SD card connected to the joystick or DSP port, and a custom BIOS would automatically program the Jagtopus PCB.

 

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10 hours ago, Sauron said:

There is definitely going to be a demand for larger cart sizes soon, you can count on it. And like you said, larger carts will be necessary once the games to take advantage of them come along, as not everyone is going to have a GD. As far as extra features go for a project like this, I'd say don't worry about them, they would probably just add to the cost of development with minimal usage at best.

Agree with this 100% - keep the cost to a bare minimum less the wonky extras or if there's enough demand for whatever else you/others can dream up, set them apart for those who request/need them. I'm not even sure what extra wants or features you would need and I always ask for more lol... what else is there?

 

Definitely want to be on board but ultimately it would depend on price. Do you have a general ballpark range? Part of the reason I proceeded to develop my own 2/4MB PCBs and now 6MB boards was because they either weren't readily available, no one would sell me any for whatever reason (like pulling teeth or just no response at all) or finally the price range was $12 for just a blank de-soldered board alone, that would then later be reduced to $8 but was still too expensive for just a blank board.

 

Please correct me if I'm wrong but we're talking about more than just a blank board here right? One that is being sold with a flash chip (x size) that just needs to be programmed? or are we to supply the chips as well?

 

12 hours ago, Zerosquare said:

Here's where I need your feedback. As homebrew developers:

- what do you think of the idea?

- would such a product be useful to you, and if so, how would you use it?

- besides the larger memories, are there any extra features you'd find useful? (please note that unlike the Skunkboard and the JagSD, this would be a cost-optimized design for releasing games, not a development tool or a multicart. So don't expect anything too fancy ;)).

Now is the perfect time for something like this to materialize.

 

My next project after the 6MB board was to figure out a 16MB bank-switching board (drop the manual switch) but this may save me from having to do that (I would be grateful), which would be really nice since it sounds like you already have the foundation (mostly) laid out and just need to pull the trigger. It also sounds like you're going to be able to go above 16MB with a design like that as well, would that be true?

 

The other benefit of this board would also be (most likely) more readily available flash chips over the "who knows when" depleting stock of 2/4MB EPROM chips that remain out there for regular boards and may finally end up being ultra scarce or eventually no more sooner than later. So it may quickly serve as a nice alternative all-around anyways.

 

15 minutes ago, Zerosquare said:

There are two existing options for programming Jagtopus PCBs:

- using an external programmer designed by SCPCD. It's a much better option for mass production, since it can program 4 PCBs in parallel. But the hardware is not cheap (the design hasn't been optimized for cost, and the 4 cartridge connectors alone are pricey).

Define "not cheap".... as in,how much exactly? :P

I think the initial cost of a custom programmer would be worth it, the problem we have now is that only a handful of Jaguar cart connectors exist as new stock, so I'm not sure where you would be able to acquire those anymore sadly. B&C has like 4 left I think and AFAIK, Best has none. I have 3 or 4 in a drawer somewhere.

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2 hours ago, Clint Thompson said:

Please correct me if I'm wrong but we're talking about more than just a blank board here right? One that is being sold with a flash chip (x size) that just needs to be programmed? or are we to supply the chips as well?

The boards would be sold with all the components soldered, you'd only have to program them. This is both for technical reasons, and because I know not all developers like playing with a soldering iron :D

 

2 hours ago, Clint Thompson said:

Definitely want to be on board but ultimately it would depend on price. Do you have a general ballpark range?

Not yet. It depends on several things: memory size, banking scheme implementation, whether I can find a factory in China with both decent quality and competitive prices (I know a few of them, but I'd have to benchmark them)...

 

2 hours ago, Clint Thompson said:

would be really nice since it sounds like you already have the foundation (mostly) laid out and just need to pull the trigger. It also sounds like you're going to be able to go above 16MB with a design like that as well, would that be true?

"Just pulling the trigger" may be optimistic ; I have the theory laid out, and a partially completed older design. It was based on discrete logic though, which may not be the best solution now that I've revisited the idea. Let's say I'm not starting from scratch :)

More than 16 MB would certainly be possible, the main limitation is memory prices (parallel NOR Flash is significantly more expensive than the serial NAND Flash that's used in memory cards and SSDs).

 

2 hours ago, Clint Thompson said:

The other benefit of this board would also be (most likely) more readily available flash chips over the "who knows when" depleting stock of 2/4MB EPROM chips that remain out there for regular boards and may finally end up being ultra scarce or eventually no more sooner than later. So it may quickly serve as a nice alternative all-around anyways.

Exactly ; not relying on old EPROMs was one of the main goal of the original Jagtopus boards, ten years ago. It turned out that the supply of EPROMs did not dry up like I was expecting (the amount of old/recycled parts you can get from China is amazing...), but you still have more guarantees with new parts.

 

2 hours ago, Clint Thompson said:

Define "not cheap".... as in,how much exactly? :P

@SCPCD is the one who designed and manufactured the programmers; I don't remember their cost exactly, but it was several hundreds euros if memory serves, not including the time he spent soldering and testing them (which is why only 3 or so of them have been manufactured).

 

2 hours ago, Clint Thompson said:

the problem we have now is that only a handful of Jaguar cart connectors exist as new stock, so I'm not sure where you would be able to acquire those anymore sadly. B&C has like 4 left I think and AFAIK, Best has none. I have 3 or 4 in a drawer somewhere.

Ouch -- I had no idea the stocks levels were so low! Thanks for the warning.

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My initial games will be small, derpy abominations.  Most likely simulating text/character graphic games of old.  So, not so concerned with extra ROM space.  But, price and save game support are important.

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2 hours ago, Gemintronic said:

save game support are important.

Oh yeah, good point. Are you gonna put a serial EEPROM on there, or would we just have to reserve a sector of flash for that kind of stuff?

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8 hours ago, Clint Thompson said:

Define "not cheap".... as in,how much exactly? :P

 

Each JagtopusProgrammer cost arround 360€ to made in 2012. Probably more now as there are obsoletes components.

 

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3 hours ago, cubanismo said:

Oh yeah, good point. Are you gonna put a serial EEPROM on there, or would we just have to reserve a sector of flash for that kind of stuff?

Yes, serial EEPROM is planned.

 

There's nothing preventing you from using a sector in the Flash chip if you want to save the cost of the EEPROM chip, but you need to be 100% sure there's no way for the code to accidentally erase/write to the wrong sector, otherwise you can end up with a game that corrupts itself - that would be  a nightmare if it happens after the game is in customer's hands. Another possible issue is that all Flash chips don't have the same blocks layout ; it doesn't matter if you always use the same chip, but we've had to change the chip model several times on the Jagtopus because the previous was either out-of-stock or discontinued.

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very interested in a new version of this,  the only thing that would be useful is a better way to program the boards. the first version seemed annoying to program.

 

being able to program / reprogram boards withoutout manual chip programming and soldering would be very useful!

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4 hours ago, omf said:

being able to program / reprogram boards withoutout manual chip programming and soldering would be very useful!

Being able to get rid of the 15 year old laptop + dock just because it has a parallel port would be very useful too :P

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I've been informed that someone else in the Jaguar community has been working on a very similar project that's almost complete -- it's just not been announced publicly yet. Since there would be no point in having two different carts that do the same thing, I'll let this person unveil their project when they're ready.

 

But I have another idea for a related project that's not quite the same thing. So, stay tuned :)

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