Mod CO12963 for EPROM

[glurk]

Ok, hardware folks.  I'm working on doing the mod here (2 links):

https://hackaday.com/2013/03/22/atari-800-eprom-cartridge-hack/

https://www.insentricity.com/a.cl/200/A800-2764

 

Specifically, I want to do this because I have a few of these boards, and a number of 2764 EPROMS.  More specifically, I'd like to put Altirra BASIC inside my Atari BASIC cart.

 

I've already removed the capacitor and the ROMs and sockets, with soldering iron and heat gun, no problem.

 

The problem is that the links given have photos, and a pinout diagram, but no writeup as to details.  It LOOKS like cutting two traces and adding some jumpers, but has anyone here done this mod and written up the procedure?  I'd rather not screw it up, and specifics would be a huge help, as per which traces to cut and what pins to jumper.  My eyesight is not the greatest these days, and I'd really like to get this to work, so any help would be super appreciated.

 

Possibly this procedure is already explained somewhere on the board here, but I did not / could not find it.

[glurk]

For documentation purposes, here is my current board.  With chips and sockets removed, capacitor replaced, and vias filled in.  The orange lines indicate where I BELIEVE the traces are to be cut.  It would be an enormous help if someone could confirm that these locations are correct!!  Before I screw up...

 

 

[xrbrevin]

check this out: (red circles on the back mean cut traces)

Edited October 9, 2021 by xrbrevin

[glurk]

OK, cool.  At first glance, this appears to be the exact same mod.  Those little red circles are hard to see, though!!

 

Is it necessary for Vpp and /PGM to get +5v??  Just want to be sure on this stuff before I make a mess.  I REALLY want this to work, LOL.  I think I have it down now, but a writeup or something would still be helpful, if anyone has one!  Thanks!

 

[xrbrevin]

click the image a second time for an extreme closeup to see the cuts more easily. i can confirm the mod works fine - i made a SALT cart and a SuperSALT cart this way a couple of years ago. the photos are of one of these, i cant recall which but they both still work fine to this day

if you ask mr robot nicely, he may make you a replica label for Altirra Basic

[manterola]

Go for it! If you screw it up, I can send you a past pixel new pcb that's compatible with brown metallic back cartridges. 

 

[glurk]

YAY!  It does work!!  And I am NEVER EVER going to do this again.  My eyes aren't up to it.  Desoldering the stuff was easy, especially with a heat gun.  And cutting the traces and "scraping" the connections, adding the socket, not too bad either.  But soldering those little jumper wires nearly killed me, hahaha..

 

Good news is Altirra BASIC 1.57 booted up immediately.  I was pretty meticulous on checking my connections.  I wouldn't call this one an "easy" project, maybe for younger folk with better vision, perhaps.

 

Next time around I'll just BUY a board.  Does anyone SELL those past pixel boards pre-made?  I'll buy a few.

[+videofx]

I have carts for sale that take 27C512, 27C256, or 27C128 EPROMS 

[glurk]

videofx-

 

Thanks, but I'm looking for really just 8K / 16K ones that will fit in an Atari cart shell, AND will fit into my original 800.  The one you posted is a bit long!!

 

I might be interested in one to do some testing with, at some later date, though.  I'll keep you in mind.

[+videofx]

Glurk,

 

I have a custom case for my cart and of course it fits in Atari 400/800

[cwilbar]

There are certain old EPROMs that are 8kilobytes (64 kilobits) that have the pinout the same as the sockets in an Atari 8K/16K cartridge.

 

It is easy for 8K cartridges if you have these ROMs and can burn them.  16K is a bit more complex as the Atari masked roms could be made to be enabled by a low or high depending on the rom they were making.

This allowed the use of two masked 8K ROMs; one active low, one active high; resulting in a 16K cartridge that needed no logic for the enables.  To use these in a 16K cart, one would need to wire in an inverter for the second EPROM chip, as the EPROMs were not available in an enable low and enable high variety like was possible with the mask ROMs.

 

If anyone is curious I can look up the number.  I sourced less than a dozen and had to do some digging where they would not cost me an appendage.  I used one to make a basic REV C cart out of an Atari 8K basic card with a bad PROM.

 

 

[glurk]

videofx-

 

Ahhh OK.  Do you have a web site, or somewhere with more info?  Does it do 8K / 16K and larger bankswitched sizes?

[glurk]

cwilbar-

 

Actually I have one (only 1) cart from "Deico Electronics" that takes 2 2764's to make a 16K cart.  They are long gone out of business, and I wouldn't mind to get another one like that too, but the Deico ones are super rare, and I don't know if anyone else makes one like it!

[xrbrevin]

6 hours ago, glurk said:

Does anyone SELL those past pixel boards pre-made? 

you can download the PCB files here:

http://www.grandideastudio.com/pixels-past/

and commission a PCB firm to make you some. they turn up in the post shortly thereafter

[glurk]

xrbrevin-

 

I looked at that (and I'm in the US) and it looks like OshPark wants $29.45 per board.  No way.  And if I download the Gerber files, try to find a more affordable supplier, and miss one little detail - I've never ordered PCB's before - then I might get unusable boards.  I'd rather leave that all to someone with more experience, lest I make a costly error.

 

So really, I'd prefer to (1) Select quantity and (2) Press "BUY" button, LOL.  Or alternately buy some extras from someone here who knows what they are doing, or some kind of group-buy or something.  I'm in no rush, in any case.

[xrbrevin]

try JLCPCB - much better value in terms of quantity as well as price

 

19 minutes ago, glurk said:

OshPark wants $29.45 per board

oh crikey!

Edited October 10, 2021 by xrbrevin

[TGB1718]

13 hours ago, glurk said:

Is it necessary for Vpp and /PGM to get +5v?? 

/PGM definitely needs +5V, I would also put +5V on Vpp for stability, I made my own EPROM programmer

and the Vpp line switches between 12V for programming and 5V for normal use.

[clh333]

Pardon me for jumping in here but I was searching for this info and stumbled across this thread.  I have only recently acquired an 800XL but soon realized there was a possibility for programming EEPROMs for use in the XL.  I found the files on Atarimania and I found (and purchased) a Pixels Past carrier board from an eBay seller (https://www.ebay.com/itm/313577226749?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649) for $10.50 plus $3.50 shipping.  The board came socketed and populated with C1 and U2 so AFAIK it only needs an EEPROM and a shell.  

 

I have an EEPROM programmer (GQ-4X) and some 2764 and 27128 EEPROMs but I don't know if these are correct for this application and I don't want to find out the hard way that they are not.  I also have noted the "2x8k ROM" distinction mentioned above so for my initial attempt I will try to find something that fits in an 8K ROM.

 

But being a complete NOOB I thought it would be a good idea if someone would pull my coat in case I am headed in the wrong direction.  Again, pardon me for butting in.

 

Thanks for your suggestions,

-CH-

 

 

[xrbrevin]

13 minutes ago, clh333 said:

Pardon me for jumping in here but I was searching for this info and stumbled across this thread.  I have only recently acquired an 800XL but soon realized there was a possibility for programming EEPROMs for use in the XL.  I found the files on Atarimania and I found (and purchased) a Pixels Past carrier board from an eBay seller (https://www.ebay.com/itm/313577226749?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649) for $10.50 plus $3.50 shipping.  The board came socketed and populated with C1 and U2 so AFAIK it only needs an EEPROM and a shell.  

 

I have an EEPROM programmer (GQ-4X) and some 2764 and 27128 EEPROMs but I don't know if these are correct for this application and I don't want to find out the hard way that they are not.  I also have noted the "2x8k ROM" distinction mentioned above so for my initial attempt I will try to find something that fits in an 8K ROM.

 

But being a complete NOOB I thought it would be a good idea if someone would pull my coat in case I am headed in the wrong direction.  Again, pardon me for butting in.

 

Thanks for your suggestions,

-CH-

 

 

for the pixels past cart, the EPROM type is 2764 for an 8k ROM or 27128 for a 16k ROM

attached is the instruction pdf it states:

 

 

if you want to use an 8k ROM but you only have a 27128 chip then merge the file to itself to double its size. this ensures the EPROM is filled when you burn it

pp_atari8bit_instructions.pdf

[clh333]

Well, I THOUGHT I had some 27128 EEPROMS but it turns out I do not.  Another item on order...  On a related topic: I found a post on thingiverse about a custom case for this board (70x55 mm, see attached):  https://www.thingiverse.com/thing:23216 but I do not have a 3D printer.  Does anyone know of a seller of these cases?

 

-CH-

 

 

[glurk]

The case you posted is for the Atari 2600, it won't fit an 8-bit Atari computer board.  You'll need these:

 

https://www.vintagecomputercenter.com/product/atari-8-bit-cartridge-shells

 

That's one source, there are others too.

 

I now have and use those PixelsPast boards, they work great.  The one you have will work 16K with the 74LS00 chip and a 27128 EPROM, or take the 74LS00 chip out and put the jumper in the socket for an 8K cart with a 2764.   Just be sure you put the EPROM chips in in the right direction and you should have no problems.

 

Here's what I use, I put in ZIF sockets.  It's an 8K left and a 16K right:

 

Edited November 6, 2021 by glurk

[clh333]

Thank you for pointing that out.  I was unaware of the difference in formats and of vintagecomputercenter.com (new to 8-bit Atari).  I have ordered some shells for my projects.

 

-CH-

[manterola]

Not sure, but I guess you don't need to take out the 7400 for 8kb eprom, if you already have it there. It should work anyways. 

It is kind of a waste, of course, but when trying different games you should be okay by changing eproms only. 

 

Edited November 7, 2021 by manterola

[glurk]

4 hours ago, manterola said:

Not sure, but I guess you don't need to take out the 7400 for 8kb eprom, if you already have it there. It should work anyways. 

It is kind of a waste, of course, but when trying different games you should be okay by changing eproms only. 

 

 

I was unaware that this would work, so I tested it, and it does.  So it's confirmed, you can just leave the 7400 in there.

[clh333]

I obtained some cartridge shells from Vintage Computer; they just arrived.  Yesterday I programmed a 2764 with ROM data from Atarimania and put it in a board.  My last question is: which way does the board face in the cartridge and which way does the cartridge face in the machine?

 

Thanks,

-CH-