6MB Cartridge - DIY options?

[phoboz]

What are the options to make a 6MB cartridge at an affordable price?

 

Are there any PCB layouts available (to share) which uses 2x 16-bit EPROM?

 

Is someone making these PCB and selling in larger quantities (e.g. a couple of hundred units)?

Edited February 6, 2023 by phoboz

[42bs]

I would say, a custom layout with a parallel flash is likely cheaper and easier to program. Just be sure to cut the write enable after production.

[phoboz]

55 minutes ago, 42bs said:

Just be sure to cut the write enable after production.

I guess a jumper pulling the WE low is a good option (if a custom design is to be made)

 

Some kind of adapter between the programmer and the cartridge would be nice.

(If it is possible to source a cartridge connector similar to the Jaguar's)

[42bs]

Those PCB connectors should be still around, though maybe not the exact size you need.

[+Stephen Moss]

Clint Thompson was working on some 6MB boards, try sending him a PM here on AtariAge or send an e-mail to info@riscgames.com.

[phoboz]

21 minutes ago, Stephen Moss said:

Clint Thompson was working on some 6MB boards, try sending him a PM here on AtariAge or send an e-mail to info@riscgames.com.

Yes there was a thread on that before, I replied to that I needed a larger quantity. I haven't heard anything more on that (got the impression that he intended to sell smaller quantities) Also I would like to avoid dual import charges, as it will affect the budget.

I guess the PCBs come from China anyway?

 

 

Nevertheless I will double check with him again in a PM.

Edited February 7, 2023 by phoboz

[phoboz]

It turns out I cannot PM him.

 

@Clint Thompson, you may contact me if you are interested?

[phoboz]

2 hours ago, 42bs said:

I would say, a custom layout with a parallel flash is likely cheaper and easier to program.

I did some research (as I am not so familiar with Flash). Is there something that can connect directly to the Jaguar's interface?

 

For example I am guessing on Parallell NOR, 64MBit?

How many address lines are needed, I guess it has to be 32 data lines?

The operating voltage seem to be 2.7 - 3.6 Volts on modern chips. Is that directly compatible with the Jaguar, or does it need to be able to handle 5 Volts?

 

PS. Excuse me for asking such basic questions when it comes to hardware...

Edited February 7, 2023 by phoboz

[Jones007]

A question from a non-expert:

Is 6 Megabytes the maximum cartridge size? Or could there be also more, via bank switching?
And if 6MB is max, does that also apply for the SD card readers?

[+Stephen Moss]

26 minutes ago, phoboz said:

The operating voltage seem to be 2.7 - 3.6 Volts on modern chips. Is that directly compatible with the Jaguar, or does it need to be able to handle 5 Volts?

For a 3.3/3.6V device the data output on the bus should be high enough that the Jaguar can read it without misinterpreting a 1 as a 0, whereas 2.7V may be a little more hit and miss but the only way to know for sure is to test it at 2.7V.

However, if address (or data) lines which the Jaguar has to write to are not 5V tolerant that could potentially result in damaged to the IC. You could look at using level translation but that requires more components = more cost and space, so you may have to go to surface mount devices to make space for everything.

[phoboz]

33 minutes ago, Jones007 said:

A question from a non-expert:

Is 6 Megabytes the maximum cartridge size? Or could there be also more, via bank switching?
And if 6MB is max, does that also apply for the SD card readers?

6MB is possible without bank switching. Larger sizes seem to be possible (I take the Jaguar GD as proof of that), but then you probably need some microcontroller in the cartridge?

E.g. I don't know if you can program the Jaguar's cartridges lines to do whatever you like.

[phoboz]

9 minutes ago, Stephen Moss said:

For a 3.3/3.6V device the data output on the bus should be high enough that the Jaguar can read it without misinterpreting a 1 as a 0, whereas 2.7V may be a little more hit and miss but the only way to know for sure is to test it at 2.7V.

However, if address (or data) lines which the Jaguar has to write to are not 5V tolerant that could potentially result in damaged to the IC. You could look at using level translation but that requires more components = more cost and space, so you may have to go to surface mount devices to make space for everything.

Yes, you probably need a 5 Volt tolerant chip then (e.g. 74HC vs. 74HCT), or making a separate voltage translation circuit as you mention.

[phoboz]

A step down level shifter can apparently be done using only 2 resistors.

 

1 hour ago, Stephen Moss said:

so you may have to go to surface mount devices to make space for everything

A design using surface monted resistors will keep the size down, even if the Flash ROM is a DIP IC.

Resistors are not that hard to solder compared to surface mount ICs.

 

So I may start trying to only do level shifting on the write signals (to avoid chip damage), and see if a logic high signal at 2.7-3.6 V will be interpreted as a logic high on the Jaguar.

 

A couple of 74HCT244 (octal buffer) may also work as level shifter.

 

PS. Anyone in Europe who are also in need of a 6MB cartridge PCB? Then we may make a combined PCB order after the design has been validated.

Edited February 7, 2023 by phoboz

[42bs]

Uh, no, no voltage divider as level shifter.
There are 5V tolerant Flash chips, maybe ask @karri a Lynx dev who did Flash-card for the Lynx. And I see no level shifter.

 

And no, no need for a uC for bank switching. You just need a latch and a decoder logic.

[Zerosquare]

7 hours ago, 42bs said:

Those PCB connectors should be still around, though maybe not the exact size you need.

They aren't. They were custom-made for Atari by Molex ; neither them, nor any other connector manufacturer I could find, had any other connector with the same pin pitch (even with a different number of pins).

 

The only source for the connector is Best Electronics. But it's not cheap, and according to someone who posted on AtariAge, they don't have any stock left.

 

3 hours ago, phoboz said:

A step down level shifter can apparently be done using only 2 resistors.

It's not reliable for fast signals. Use a proper voltage-translator chip, they're not expensive.

 

Also, if you use modern Flash memory chips, you're basically recreating the Jagtopus (albeit with 6 MB instead of 4 MB). It may not be worth reinventing the wheel from scratch. (Hint, hint.)

Edited February 7, 2023 by Zerosquare

[Zerosquare]

Also, be aware that the current semiconductor shortage is hitting hard on memory chips. Sourcing them is an issue (unless you're OK with buying zero-guarantee stock from China, maybe...)

[42bs]

1 minute ago, Zerosquare said:

They aren't. They were custom-made for Atari by Molex ; neither them, nor any other connector manufacturer I could find, had any other connector with the same pin pitch (even with a different number of pins).

Isn't it just an ISA slot?

 

Ah, no it seems the pitch is slightly smaller

 

So it is likely easier to add a second connector to the PCB.

 

[neo_rg]

There is a severe shortage of memory chips at the moment. You can get some but you'll pay a premium price + import duty. I'm glad I got a bucket load a few years back. 

[phoboz]

2 hours ago, Zerosquare said:

Also, if you use modern Flash memory chips, you're basically recreating the Jagtopus (albeit with 6 MB instead of 4 MB). It may not be worth reinventing the wheel from scratch. (Hint, hint.)

Yes, a 6MB Jagtopus would be nice. Perhaps also with a larger EEPROM for save data.

 

6MB would still be a considerable improvement over 4 MB, without any additional programming effort (such as bank switching)

 

1 hour ago, 42bs said:

So it is likely easier to add a second connector to the PCB

Sounds like a good improvement for the original Jagtopus, to avoid the need for a BJL modded Jaguar, an old PC with parallel port, and a PC to Jaguar joystick-port cable (unless you have the dedicated programmer)

 

2 hours ago, Zerosquare said:

Also, be aware that the current semiconductor shortage is hitting hard on memory chips. Sourcing them is an issue (unless you're OK with buying zero-guarantee stock from China, maybe...)

Yes, that's why it is still an interesting option to use good old EPROMs. Because these chips (sold from China) are not really affected by the semiconductor shortage.

 

On the other hand, you may end up getting used chips (with a fresh print on), marketed as NOS. I used this method in the past, and 1 in 10 chips had to be thrown in the waste bin.

It's also a time consuming and tedious process to program them, solder them, test the game etc.

Edited February 7, 2023 by phoboz

[42bs]

1 hour ago, phoboz said:

6MB would still be a considerable improvement over 4 MB

With a good compressor it is worth 8MB

[Zerosquare]

11 hours ago, phoboz said:

Perhaps also with a larger EEPROM for save data.

I already have a working solution for this. It requires only minor hardware and software modifications.

 

13 hours ago, 42bs said:

So it is likely easier to add a second connector to the PCB.

11 hours ago, phoboz said:

Sounds like a good improvement for the original Jagtopus, to avoid the need for a BJL modded Jaguar, an old PC with parallel port, and a PC to Jaguar joystick-port cable (unless you have the dedicated programmer)

Good points. A simple and cheap programmer would be useful as well.

[phoboz]

18 hours ago, 42bs said:

There are 5V tolerant Flash chips, maybe ask @karri a Lynx dev who did Flash-card for the Lynx.

I found a few 5V Flash memory chips, but most of them have low memory capacity.

 

The largest one I found was 16Mbit, so several chips would be needed for a 6MB cartridge.

Edited February 8, 2023 by phoboz

[42bs]

10 minutes ago, phoboz said:

I found a few 5V Flash memory chips, but most of them have low memory capacity.

 

The largest one I found was 16Mbit, so several chips would be needed for a 6MB cartridge.

Are those 16bit wide? Or only 8bit?

Anyway, 74hct's to convert 5V > 3v3 will be likely cheaper.

 

Edited February 8, 2023 by 42bs

[phoboz]

2 hours ago, 42bs said:

Are those 16bit wide? Or only 8bit?

The one I checked (A29160B) appears to be usable either as two 8-bit, or one 16-bit memory.

Edited February 8, 2023 by phoboz

[42bs]

This chip is only 16Mbit!

 

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

 

Edited February 8, 2023 by 42bs