6MB Cartridge - DIY options?

[Seedy1812]

Don't just think about using a larger cart but whether you can use compressed files to get the game onto a smaller cart. Bubsy unpacked is about 8 meg and those files easily compress onto a 2meg one.

[Zerosquare]

46 minutes ago, Seedy1812 said:

Bubsy unpacked is about 8 meg and those files easily compress onto a 2meg one.

Bubsy could be compressed into a zero byte file with no loss of enjoyability.

[Fadest]

6 minutes ago, Zerosquare said:

Bubsy could be compressed into a zero byte file with no loss of enjoyability.

This is wrong !

You would have lose some nice AC discussions then

Which are my best memories of Bubsy (and of course SuperCross 3D among others Jag games...)

[Seedy1812]

We used to joke about compression , using fractal compression we could pack any file into the same 4 bytes 😮

[Seedy1812]

Atari had a great idea to cut down rom space for sprites. You have a 1 bit alpha channel and then for the colour / image -  pack it with the cinepack bpeg compressor ?!?!

Edited February 8, 2023 by Seedy1812

[phoboz]

The lz77 packer is actually a quite good, lossless packer. I use it for all graphics and the size become 20-60% of the original size.

 

I have been fighting with the 4 MB limit for the last 2 games (even if I compress all graphics). Having these 2 extra megabytes will help a lot for future projects, as it gives 50% space.

 

Much more size than 6MB is probably not needed for games that don't have movie sequences etc. (Like CD games)

6MB is usable on the Jaguar without the need for extra programming tricks, like bank switching. So the ultimate Jaguar cartridge is 6MB in my opinion.

[phoboz]

4 hours ago, 42bs said:

This chip is only 16Mbit!

 

Oops, you wrote it. So 2 chips for 4MBytes/32Bit.

 

Yes, so this will be just like the existing solutions. Not 6MB yet...

Then a voltage level shifter is needed after all.

[42bs]

Well, 6MB of compressed game + assets, what a hell of a game are you going to write?!

 

[+CyranoJ]

54 minutes ago, 42bs said:

Well, 6MB of compressed game + assets, what a hell of a game are you going to write?!

 

[Seedy1812]

Isnt a 6MB cart  = 48 Mega bits - so 350 Mega Bits = 43.75 Mega Bytes - wow thats a lot of content.

[42bs]

24 minutes ago, Seedy1812 said:

Isnt a 6MB cart  = 48 Mega bits - so 350 Mega Bits = 43.75 Mega Bytes - wow thats a lot of content.

But Australian bits. These are less more than US American bits.

Edited February 9, 2023 by 42bs

[Cyprian]

I wonder whether would be possible to use cart ROM bank swapping, as it is done in case of Atari XL and Atari 7800 cartridges

[Zerosquare]

4 hours ago, 42bs said:

But Australian bits. These are less more than US American bits.

That's nonsense. They're exactly the same size as American bits, they're just upside-down.

[Zerosquare]

4 hours ago, Cyprian said:

I wonder whether would be possible to use cart ROM bank swapping, as it is done in case of Atari XL and Atari 7800 cartridges

Yes, it's possible. I have designed some logic for it, but not tested it yet.

[+cubanismo]

Yeah, if you can find a fast 16-bit 8MB/64Mbit flash like the Skunkboard uses, an 8mb bank switched cart makes more sense as long as you can implement cheap bank switching logic. Otherwise you usually end up wasting 2mb with common flash sizes, no? And 16bit at double the speed is as good or better than 32bit at normal ROM speeds in theory.

 

Edit: Extra points if you can design a PCB where you can build it as either a 6MB cartridge or a 8MB cartridge using the same flash chip, just by changing which components you solder down.

Edited February 10, 2023 by cubanismo
New idea

[Zerosquare]

11 hours ago, cubanismo said:

Yeah, if you can find a fast 16-bit 8MB/64Mbit flash like the Skunkboard uses, an 8mb bank switched cart makes more sense as long as you can implement cheap bank switching logic. Otherwise you usually end up wasting 2mb with common flash sizes, no?

Yes. For 6 MB you have two solutions:

• Use a 4 MB chip and a 2 MB chip
• Use a single 8 MB chip

Since the second solution is both simpler and cheaper than the first one, there's no reason not to go 8 MB.

 

11 hours ago, cubanismo said:

Edit: Extra points if you can design a PCB where you can build it as either a 6MB cartridge or a 8MB cartridge using the same flash chip, just by changing which components you solder down.

You don't even need to anything, as long as you make sure the default configuration maps the first 6 MB of the Flash memory to the 6 MB address space. Games made for 6 MB don't attempt to bank switch, and thus won't even be aware than there is more than 6 MB of data accessible.

Edited February 10, 2023 by Zerosquare

[+Gemintronic]

Are there repro boards out there that support save games?  I could see a JagStudio runtime with support for loading game logic and custom assets from an EEPROM (hopefully much bigger than the 93LC46.)

 

..but, that's because I have no idea what  I'm talking about.

[Seedy1812]

58 minutes ago, Gemintronic said:

Are there repro boards out there that support save games?  I could see a JagStudio runtime with support for loading game logic and custom assets from an EEPROM (hopefully much bigger than the 93LC46.)

 

..but, that's because I have no idea what  I'm talking about.

128 x 8- or 64 x 16-bit organization (93LC46)  Note thats only 128 bytes of memory - you're not going to store much on that .

There was the memory track ( http://kick-ass.asuscomm.com/html/library/documents/mt.pdf ) which according to the pdf has over 125,000 bytes of storage  .. for up to 250 games.

[+Gemintronic]

12 minutes ago, Seedy1812 said:

128 x 8- or 64 x 16-bit organization (93LC46)  Note thats only 128 bytes of memory - you're not going to store much on that .

There was the memory track ( http://kick-ass.asuscomm.com/html/library/documents/mt.pdf ) which according to the pdf has over 125,000 bytes of storage  .. for up to 250 games.

 

I knew the 93LC46 was tiny.  Just wasn't sure if bigger EEPROMs could be a drop in replacement.  Maybe using some sort of JTAG or a BJL modded Jag to program the memory?

 

Memory Track sounds larger but seems like you'd have to own (and use simultaneously) both the "game engine" cart and the memory track.  Probably super rare by now as well.

[Songbird]

On 2/7/2023 at 10:37 AM, phoboz said:

Perhaps also with a larger EEPROM for save data.

Protector SE already uses the 93c86 EEPROM (2048 bytes) for saves, even though sadly most of that space goes unused... anyway, the point is it's easy to swap in this part as long as the ROM supports the bigger EEPROM.

 

[Seedy1812]

The JagStudio docs say only a 2k eeprom will is supported . Without reading the full docs only 1 type of eeprom may be supported -  They come in 2 flavours 8 or 16 bits , each one would require different read / writing functions (  it might writes 8 or 16 bits at once )

 

 128 x 8- or 64 x 16-bit organization (93LC46)
 256 x 8- or 128 x 16-bit organization (93LC56)
 512 x 8 or 256 x 16 bit organization (93LC66)

[Seedy1812]

2 minutes ago, Songbird said:

Protector SE already uses the 93c86 EEPROM (2048 bytes) for saves, even though sadly most of that space goes unused... anyway, the point is it's easy to swap in this part as long as the ROM supports the bigger EEPROM.

 

As I just pointed out the layout of the eeprom 8 or 16 bits , number of memory location would require different epprom read/write code . I guess this is why the 2K eeprom was picked. I assume its the 8 bit version.

[Songbird]

Yep, and I publicly released the assembly code to support the 93C86 read/write operations some years ago. I think the only minor issue with it is it has a really long hard-coded delay while waiting on a write to complete. This delay can be shortened quite a bit in practice.

[Seedy1812]

6 minutes ago, Songbird said:

Yep, and I publicly released the assembly code to support the 93C86 read/write operations some years ago. I think the only minor issue with it is it has a really long hard-coded delay while waiting on a write to complete. This delay can be shortened quite a bit in practice.

Hehe i noticed you released a lot of code  People were asking when I was going to release code to the games I written and said I was not in a hurray - but somebody pointed out it already was available ..  I wonder by whom  lol

Edited February 10, 2023 by Seedy1812

[Zerosquare]

The largest EEPROM which is a drop-in replacement is indeed the 93LC86, which stores 2 kilobytes. Larger EEPROMs are not available with a Microwire interface, which is what the Jaguar carts were designed for.

 

Using a SPI EEPROM instead would allow much larger sizes, but requires a bit of extra logic on the cart. But now that you mention it, it would be possible to make a very small PCB with the SPI EEPROM and the logic, that could be soldered where the original EEPROM normally is. That would allow upgrading existing cartridge PCBs.

 

I wouldn't rely on it to store game code or data, though -- the data path is only 1-bit wide, and it's slow to access.

Edited February 10, 2023 by Zerosquare