The Persistent RAM Cartridge

[+Nezgar]

I have a gem here readers may be interested in - The "Persistent RAM" cartridge by Intra-Tech Computer Products. There appears to be literally no information about it online. Only a single entry on AtariMania with a picture and no other information. Probably considered 'Rarity 10'. There is only two mentions of it on all of the AtariAge forums, in cart lists with no information, and 'no ROM dump' - which I thought was funny (since it's RAM).

It operates passively in the "RAM" mode, and you can load up any standard cartridge based code into the 8K or 16K address space, and flipping the switch to the "ROM" position 'locks it in' to static battery-backed RAM and then operates as an 8K or 16K ROM cartridge. IE - Load the 8K Track & Field, or 16K Pitfall II, flip it to ROM, and when you turn the computer off, and back on again, and instantly you're back in the game as if it is a real ROM cart.

I can see this would have been invaluable for a software developer working on a cartridge title! As long as there is a valid Cart init/entry point intact, it would work. Most XEX games that originated from Cart dumps that leave the original code in the $A000-$BFFF (8K) or $8000-$BFFF (16K) range should work. XEX loaders often have extra initialization code placed elsewhere in RAM, that obviously gets discarded.

I used this as a kid to load games off of tape or disk, and then keep it as a 'virtual cartridge' for instant load the next time. It was neat to be able to change up which 1 game was on it.

The original battery was a 3V lithium cell soldered directly to the PCB, but I replaced it with a ginormous CR123A battery ages ago and attached it externally with hot glue which was long since dead. I just replaced it with a new CR2032 cell holder recently after ordering 4 different types to see what would fit inside the cart shell, since I really didn't want to solder a battery directly to the PCB, which I think was the original configuration... well I got one to fit, and confirmed it still works!

The PCB appears to consists of just 2 8K SRAM chips, and some simple logic chips, a diode to protect against reverse battery polarity, and a capacitor. The solder work was originally really messy, and looked like a lot of old (acid based?) flux was left, indicating quick work. I spent an evening cleaning it all up with isopropyl alcohol, and reflowing solder. After first replacing the battery, I did have some strange issues with the computer not booting up occasionally, but that all seems to have cleared up after time, maybe from corrupt RAM in the cartridge memory space.

I've taken some pictures of the internals as well, lifting up my battery holder so all of the PCB is visible.

My dad who acquired it originally back in the day thinks it was created by a local hardware guru in the Vancouver, BC (Canada) area he knew, but pretty hard to confirm nowadays... may be the same guy that created clone Happy PCB's he had some of, one of which I still have.

I tested a bunch of XEX titles on it last night, there's a lot of stuff that doesn't work (Probably not originated from a cartridge release), but here is a small list of ones I found that do work:

8K:

• Atari Assembler Editor
• Atari PILOT
• Atari Centipede 81 or 82
• Demon Attack
• Activision MegaMania

16K

• Atari Centipede
• Activision Decathlon
• Defender
• Diamond Mine
• Atari Dig Dug
• Donkey Kong Jr
• Atari Football
• Matterhorn
• Miner 2049er
• Ms Pac Man

Maybe someone with experience in PCB design would be interested in replicating it. Maybe others would be interested in acquiring those replicas. Looks like only a few pretty cheap components.

Curious to hear if anyone else out there knows any additional history about this cart, and thoughts on it's workings / design!

 

Cheers,

Ryan

[Tinman]

Neat!

[+MrFish]

Thanks for sharing, and the pics.

 

It's listed on Pitfall Jones' site, and you can see a picture by click the link for it.

No information there though. He really just wanted to make record of as many

carts as possible. A lot of the pictures on his site were obtained from members

here on AtariAge. So it's quite possible the picture original appeared in the

thread he started here, asking for pictures of carts. I'm not sure if there might

be information there or not.

 

I could find it, but I gotta sleep now... Zzzz...

[+MrFish]

OK, one more bit of information here: AA member AtariGeezer mentions having one. Maybe he has some info to share about it.

 

[Edit: That was back in 2016, posted here -> Rarest A8 Carts (Post #25)]

Edited January 21, 2019 by MrFish

[Wrathchild]

The S/XEGS RAMCART 128KB by C.P.U. seems an evolution of such a device

[Gunstar]

It looks to me like The!Cart supersedes persistent Ram cart and Ramcart these days...

[+Nezgar]

The S/XEGS RAMCART 128KB by C.P.U. seems an evolution of such a device

Interesting read! I never knew about this one. More complicated, but the pictures don't look like that much more component wise.

 

It looks to me like The!Cart supersedes persistent Ram cart and Ramcart these days...

Haha, I agree -- I was not trying to imply that this could compete in any way to a modern flash cart

 

But for a fun 8K or 16K novelty... 2x6264 static rams, 74LS04N, 2 switches, and a 3V lithium cell are pretty cheap common components available today.

[+Nezgar]

supposedly AtariMax uses the exact same Solakian type mold shells:

http://atariage.com/forums/topic/146490-spectraview-1-and-2-info/?p=2964166

 

(if new ones were to be made)

[E474]

Hi,

 

The S/XEGS RAMCART 128KB looks like a fun project, although it isn't as highly specced as alternatives such as The Cart!. etc., it had a build cost of 8 euros at the time, so I wonder what it would cost now to produce?

[E474]

Hi,

 

Could the S/XEGS Ramcart 128KB be used to hold a version of SpartaDOS X, and would it be difficult to up the memory to say, 256KB, and have the cartridge act as a writable disk/file system which also holds SpartaDOS X?

[800_Rocks]

I found one on an online auction.  Here's a link to the post I started.  See pictures over there.

Nezgar I would be very interested in your parts list and instructions on removing the orig battery and adding the new one replaceable one like you did.  Thanks!!

 

Edited November 14, 2019 by 800_Rocks
added info

[Vectrexer]

Cool cart.

[Mclaneinc]

Funky cart, missed this the first time, I'm stunned there were not more of these types of products on the market, ram wasn't that expensive (more than now I expect but not massively expensive) and the rest of the bits were pence (bar the PCB).

 

 

[+ZuluGula]

There's new version of RAM cart made currently.

https://atarionline.pl/forum/comments.php?DiscussionID=5337

[+Nezgar]

It's not as fancy as a modern multi-cart or RAM cart, but a nice simple 8K/16K tool. Could be useful for 8K/16K cartridge software development with the ability to instantly make changes to the cartridge area in memory, switch it to "ROM" and reboot. My Persistent RAM pictured in the OP is actually in the hands of @Dropcheck at this time to take a look at for potential eventual reverse engineering / replication if/when time allows.

 

I have fond memories as a kid waiting 15+ minutes for Pitfall II to load from cassette, and then "locking it in" with this Cart so it could be brought up instantly from that point forward... And also the time where we got to the 2nd level "The lost caverns" and never turning the computer off for a week so we didn't have to start over...

 

On 11/14/2019 at 5:20 PM, 800_Rocks said:

Nezgar I would be very interested in your parts list and instructions on removing the orig battery and adding the new one replaceable one like you did.  Thanks!!

Missed this comment before - after desoldering the original battery, I simply replaced it with a CR2032 battery holder to avoid soldering another battery directly in - after ordering a half dozen types, here is the type I found will fit inside the shell:

https://www.ebay.com/itm/402382571996

 

(I bent it upwards for the purpose of the pictures above)

[Steen Hansen]

The Programmer's Story.

 

The Persistent RAM was like the current flash drive, but had its own 8k DOS and file system; it was just a normal cartridge to the Atari-OS. Other companies hooked into the SIO system so they could avoid a lot of assembly language by having the OS figure out where to put/get data in memory, but that was slow as that was single bit-by-bit. We moved 254 bytes at a time via CIO. Faster than the Happy-Drive. For the life of me I cannot remember how it would know where to put and get the data in memory. We used to load some games literally in a second or two as

it was basically memory copying.

 

I used to scan the assembly code for possibilities of regaining a few bytes to make the on screen instructions longer to make more sense.

For instance:

    LDA 0
    LDX 0
    LDY 0

Could be re-written, saving two bytes, as
    LDA 0
    TAX
    TAY

 

And that was a huge win for me at the time. Kinda weird as most icons on browser tabs are larger than 8K now. The print-out of the whole program was nearly a block long. There was no source control; once I accidentally changed a TAX to TXA and it took me days to find the bug.

 

When booting it would use the last few bytes of the stack for variables, then later the cassette buffer was used to transfer data from the files on the cartridge to memory. The DOS was in $A000-$BFFF which meant code had to be set up to transfer data from the cartridge to memory at possibly in $A000-$BFFF. So when loading a file into the Atari, the correct data bank would be selected, then 254 bytes would be copied to the cassette buffer, then the program would jump out of the cartridge, turn the cartridge off, copy the cassette buffer data into the now normal ram maybe at $A000-$BFFF, then the cartridge would turn back on to get the next block of data. Until all the data was moved to or from the cartridge.

 

The one big problem we had was that if the cartridge DOS got corrupted then it could only be fixed by jamming in the cartridge to an already turned on computer. Nothing ever bad happened, but man that was scary to do. A big floppy disk with the DOS came with the cartridge in case of reprogramming being needed. Oh, yeah, I remember now, when the battery died this was a distinct possibility.

 

>>>I'm stunned there were not more of these types of products on the market
There were three companies I know of in Canada. I re-wrote our code and sold it for $500 to a competitor in eastern Canada, he was
smarter than we were, he got government money, I only learned 6502 assembly. His original code used SIO, but he couldn't get it to work.

 

>>>ram wasn't that expensive
Static RAM prices went stratospheric after an earthquake hit the major producing factory in Japan. I wasn't normal ram, it was "persistent" :-)

 

The main cause of Persistent-Ram's demise was really 16-bit computers, as everyone who had money moved on. I got an Atari-ST, the Amiga was too expensive. Our most interesting sale was to a doctor in Syria. Funny, it was developed in Coquitlam BC Canada, then I moved away for like 20 years and now I am back.
Steen