Multicart(s) suggestions?

[phoenixdownita]

I'm going to rip out a few 7800 carts in order to make multicarts.

 

My idea is to rip out a 32KB cart (Food fight) and replace the ROM with a much bigger EPROM (512KB) to contain all 16Kb and 32 KB games (there's 16 of them in total).

Also I plan to do the same to a cart [hattrick] to contain all 48KB games (there's 8 of them in total, make 48KB to 64KB and you get again 512KB EPROM [27C040]).

 

Also I am planning to do the same once more to a couple of 128KB game carts (assuming a supercart PCB with support for page 6 at 4000-7fff) and replace the ROM with either a 27c080 or 27c801 [whichever I find] and have 8 128KB games in one.

 

Finally I plan to use one 128KB + 16KB RAM cart [i believe Winter Games matches the spec, I just bought one on eBay, we will see if it all pans out] and replace the ROM with an EPROM [27c040] to host 4 128K + RAM games (there's really not that may [like 5 of them excluding Plutos/Syrius], and some of them are only 64KB [Tower Toppler], I plan to copy the first 64KB in the second half).

 

That is a total of 4 multicarts: 1 to replace all 16/32 KB games (the 16KB games will be "doubled" to occupy 32Kb), 1 to replace all 48 KB games,1 for 8 "ROM only" 128KB games and 1 for "128KN RAM + <=16KB of RAM" games.

 

Any gotchas I should be looking for?

Like games that do not work if the aforementioned configuration (double 16K to 32k) or some special 48K games or 128K + 16K RAM that do not really work (like they have only 8KB RAM mapped twice and they write at the upper bank but read at the lower [mean thing to do but works well as a copy protection])?

 

I really want to get rid of many 7800 carts and replace them with a few multi, ideally if "H2 sans Pokey" would come out I would be happy, but in its absence and excluding weird mapping (2 activision games + another I can't remember right now) I can get by with multicarts with physical dip switches to choose the game.

 

It seems quite easy to me to desolder the ROM, replace with a bigger EPROM and rewire the /OE (A16) signal as appropriate.

 

What do you think? Should I butcher a few cheap 7800 carts or design my own PCB (which I have never done before)?

 

[needless to say any Pokey game is excluded]

Edited April 7, 2014 by phoenixdownita

[phoenixdownita]

1st attempt FAILED.

 

What I did:

1) use a Pole Position 2 cart.

2) remove the ROM

3) solder a socket

4) use a 64K EPROM with A15 [pin1] in pull up [2.2K]/GND to simulate 2 ROMs, I burned KF Master and Choplifter

5) I noticed that A15 from the slot went straight to the ROM pin 22 (which is supposed to be /OE) so I assumed that the stock ROM has OE and not /OE (negative) [only reason to connect it straight to A15]

6) I intercepted A15 from the cart slot and instead to go straight to pin22 on the EPROM (which is /OE) it goes thru a 1 transistor inverter [with a 1K resistor on the collector]

 

Unfortunately it does not work, anyone can help shedding a light?

 

My EPROM is a 27C512 10nf. The transistor a 2n222.

So the EPROM is good up to 10MHz, I beleive at the most the 7800 access at 2MHz.

I am not sure if my home made 1 transistor inverter with the 2n222 and 1K is fast enough.

 

For the content I use the a78 files from the goodset, I simply drop out the header and burn them as they are, I tried swapping the first 16KB with the second 16KB as a test but still nothing.

Are A78 usable as is or do I need a tool to go back to generate a BIN out of them?

 

What am I doing wrong?

For 32K games there's really nothing in the cart, just the ROM (and 1 capacitor), so replacing it with an EPROM should be piece of cake.

 

Any help greatly appreciated.

[phoenixdownita]

I should add I do not have a resistor in base, probably I should put a 10K there as suggested by many online resources.

[Shawn]

Someone else is already making all these carts currently as a 30th Anniversary deal, just buy those

and save yourself the headache. It could also come off as being rude asking about doing such with

someone else on the forum actively doing so already. Not saying that is your intent just an FYI.

[Shawn]

I "suggest" checking out this thread and buying from this user: http://atariage.com/forums/topic/224186-would-anybody-be-interested-in-this-30th-anniversary-multi-ended/

[ColecoGemini]

Someone else is already making all these carts currently as a 30th Anniversary deal, just buy those

and save yourself the headache. It could also come off as being rude asking about doing such with

someone else on the forum actively doing so already. Not saying that is your intent just an FYI.

sounds like he's trying to learn how to do this, not trying to steal anyone's business away.

[Shawn]

sounds like he's trying to learn how to do this, not trying to steal anyone's business away.

 

I don't think he's trying to take anyone's business either, I made sure I mentioned that, some people could think that though.

A couple pull up resistors and a dip switch box isn't gonna hurt anyone.

[phoenixdownita]

Exactly.

I want to do my own carts and put on them what I want.

 

I'm taking the easy route of simply swapping ROM for bigger EPROMs and use dip switches as selection. Caveat is that I can only use compatible games for the cart

(so all 32K together, likely all 48K together, then the 128K without RAM, then the 128K + RAM, given there's no EPROM to hold all 128K without RAM [i count 20+] I see at least needing 2 to satisfy my own taste in game selection).

 

On a different note even if I intended (which I don't) to make them available the fact that one (pretty good) member is already doing something along those lines means nothing.

Seriously, this forum is open to anyone and overlapping businesses are not an issue, as they shouldn't be.

 

I have no intention to "steal" anyone's business, just messing around with electronics, it's more fun that way.

 

BTW I did ordered single inverter ICs (74HCT1G04GV in specific, 10 of them for 3.99), just in case my home made one is too slow for the task, I am just asking if what I am doing is sound, at least in theory.

I just rediscovered the main purpose of the base resistor so I will try it, I could also use a Schottky diode between Base and Collector but I am just trying to limit the number of components to the minimum needed to get the job done.

Edited April 16, 2014 by phoenixdownita

[Shawn]

nm.

[phoenixdownita]

2nd attempt: still NO GO

 

I simply put a 10K resistor on the base of my inverter (on A15 from the cart connector) but still nothing works.

 

I really thought replacing a 32K ROM, no banking, no frills game with an EPROM would be the easier thing to do .... apparently not so much.

 

Is there any trick I need to know, maybe with regard to the A78 files? As I said I simply drop the 128byte header and use them straight to burn the EPROM.

 

[bTW this is an NTSC console, and I am using 27C512 10F1 EPROMs]

 

Any help greatly appreciated, I am really trying to consolidate all of my 7800 carts into few self made multi.

1 512K EPROM would be able to contain all 32K games (12) and all 16KB games (4).

1 512K EPROM would be able to contain all 48K games (there are 8 I believe) [excluding ballblazer]

 

So 2 multi could replace 32 originals ... if only I could get this thing to work as expected.

 

[Obviously I did try to take away the inverter and let A15 connect to /OE as on the ROM but as expected it doesn't work]

Edited April 17, 2014 by phoenixdownita

[Shawn]

A78 files have a header you need to strip off before burning them.

[phoenixdownita]

I contacted Dan Boris (at http://www.atarihq.com/danb/a7800.shtml) and he pointed me to:

 

 

So what I am doing is indeed correct (and he confirmed dropping the header it's all that is needed).

I guess I need a real inverter. RTL inverters may be well too slow for the task at hand.

 

We'll as soon as it arrives I'll try and see what happens.

Luckily I have a few 32K carts to sacrifice if it comes to that.

Edited April 17, 2014 by phoenixdownita

[Shawn]

pretty much any 74LS series inverter will work (00,02, 04,ect). Its the HC ones that you will find won't work.

Hell even 2 resistors and a transistor will do the job.

[phoenixdownita]

pretty much any 74LS series inverter will work (00,02, 04,ect). Its the HC ones that you will find won't work.

Hell even 2 resistors and a transistor will do the job.

Nope, 2 resistors and a transistor didn't work for me.

[10K in base, 1K on collector, and a 2n2222 transistor, no go as I reported above, it could be the response is too slow, check here http://www.physics.ucdavis.edu/Classes/Physics116/RTL_slides.pdf from saturation it takes 150ns to start rising and another 100ns to finish]

 

Also 74LS00 is quad NAND, 74LS02 is a quad NOR, yes they both can be configured as NOT (inverters) by tying their input (http://www.instructables.com/id/Using-a-NAND-or-NOR-gate-as-a-NOT/) but at that point may as well buy the correct 74LS04.

 

The issue with the HC series is they are CMOS so there's trouble with TTL values.

Edited April 17, 2014 by phoenixdownita

[phoenixdownita]

Victory .... somewhat

 

Managed to get hold of a few 74LS04 inverters and tried one.

I prepared a 27C512 with Choplifter and Kung Fu Master.

Put the inverter on A15 from the cart connector thru to /OE on the EPROM (as per video/expected) and everything works!

 

For now I switch the 2 games with exposed wires .

 

Next: replace the 27C512 with a 27C040, 8 times bigger and 4 dip switches for a total 16 games, only incognito is if the 4 16KB games once doubled to 32K need to be re-signed in order to work or not.

 

The plan is more ambitious though.

 

I desoldered HatTrick to use with a 27C040 for all 48K games at once (8 of them).

 

I also desoldered Xenophobe for use with a 27C801 (twice bigger that 27C040) to put 8 128K games on it. I already have a Dark Chambers ready to desolder and get me a second selection of 8 128KB games.

 

Lastly I managed to half mess up desoldering Winter games , I got the ROM chip out but also 6 or 7 traces/via with it .... now I will have to reconstruct the paths .... this one was to be used with a 27C040 for the 4 128K + RAM games (Mission [im]Possible, Winter Games, Summer Games and Tower Toppler [really 64K], not sure it's worth trying Plutos or Sirius), will see if I manage to "fix" my royal fuxk up.

 

At this point I really wish I knew how to design PCBs, soldering anew is so much easier than desoldering if you try to save the PCB or the ROM or both

Edited April 22, 2014 by phoenixdownita

[Shawn]

Nope, 2 resistors and a transistor didn't work for me.

[10K in base, 1K on collector, and a 2n2222 transistor, no go as I reported above, it could be the response is too slow, check here http://www.physics.ucdavis.edu/Classes/Physics116/RTL_slides.pdf from saturation it takes 150ns to start rising and another 100ns to finish]

 

Also 74LS00 is quad NAND, 74LS02 is a quad NOR, yes they both can be configured as NOT (inverters) by tying their input (http://www.instructables.com/id/Using-a-NAND-or-NOR-gate-as-a-NOT/) but at that point may as well buy the correct 74LS04.

 

The issue with the HC series is they are CMOS so there's trouble with TTL values.

 

When I mentioned using the various chips I said so in case you didn't have access to the 04's and 00's or 02's where easier to find. Sounds like you are answering my statements as if they where questions giving answers that I obviously already know. With that said, You must have this all under control and I'll just refrain from posting anything else in this thread you where asking for help in. best of luck with your project.

[phoenixdownita]

 

When I mentioned using the various chips I said so in case you didn't have access to the 04's and 00's or 02's where easier to find. Sounds like you are answering my statements as if they where questions giving answers that I obviously already know. With that said, You must have this all under control and I'll just refrain from posting anything else in this thread you where asking for help in. best of luck with your project.

 

Apologies if I sounded insulting or full of contempt, I tend to get over excited and a little cocky as I learn new things, no offense meant, really.

And thanks for lending a helping hand, I really thought the transistor inverter (RTL) would work, likely just too slow, oh well, now I know.

[Shawn]

oops wrong thread

[phoenixdownita]

I guess I should have done more research to start with and I would have found:

http://atariage.com/forums/blog/302/entry-6310-creating-custom-7800-cartridges/

which links to http://atariage.com/forums/index.php?app=core&module=attach&section=attach&attach_id=135945

that has a whealth of info I had to rediscover ... oh well.

[phoenixdownita]

32K or less multi cart is ALIVE

 

The EPROM I received are marked as AM27C040 but they really are Fairchild FM27C040 (took me a while to figure this out).

 

It took almost 3H only to adapt the plastic cartridge (the hole for the switches plus a way to cable them up, grinding here and there to make sure it all fit as I mounted the EPROM on a socket).

The change to the Pole Position 2 ROM board were not that many in the end and the only other component used beside the pullup resistors and the 4 dip switch was the 7404 inverter on /OE [from A15 on 7800 side].

 

There are 16 games in total that are 32K or less, in specific 12 are 32K and 4 are 16K. For the 16K games I simply doubled them up by copying the ROM back to back twice (made 32K out of 2 copies of the 16K) and the 7800 still likes them [i guess the signature check somehow is driven by the game, how else would the 7800 know how many 16K pages are used].

 

Anyway the list for the games in the cart is:

Asteroids (16K)

Centipede (16K)

Choplifter

Digdug (16K)

Food Fight

Galaga

Joust

Kung Fu Master

Ms Pacman (16K)

Pete Rose Baseball

Pole Position 2

Robotron 2084

Super Skateboardin'

Titlematch

Tomcat F14

Xevious

 

Next multicart, the 8 48K games and another 27C040. I have a superboard for it (HatTrick), hopefully this time I won't even need the inverter on OE, time will tell. The plan is to make all of them 64K long by prepending 16K of zeroes and simply burn them one after the other and use 3 dip switch to select which 64K the 7800 sees (same exact logic as per the 32K multicart as I'm letting the supercart components of HatTrick do the bankswitching within the 64K)

Edited May 4, 2014 by phoenixdownita

[CPUWIZ]

There is no bankswitching on 48K games, they occupy the region of memory, from $4000-$FFFF.

[phoenixdownita]

You are very right, I meant to say address decoding.

 

For 32K there is no decoding logic at all on the card, A15 is used as OE directly and that's it.

But for 48K there needs to be more decoding as in OE = [(A15) OR (/A15 AND A14)], my Hat Trick super cart is a C100339 and apart from the ROM chip it has only the 74LS02 chip populated which thus does the decoding.

 

My layman plan is as per the 32K to simply replace the ROM with a 27C040, leave the 74LS02 do the decoding (maybe interpose an inverter if needed on the /OE path to the EPROM), and put dip switches on A18/A17/A16 of the EPROM.

 

Pretty lame I know but functional enough for me.

[CPUWIZ]

The easiest way to decode 48K is to do: !OE = A15 | A14.

[phoenixdownita]

Nice simplification, and it explains the choice of Atari of an 74LS02 which is a NOR (so I bet it gets OE), likely I need an inverter again.

 

Thanks for the help.

 

 

EDIT: actually A15|A14 seems to be OE (and not /OE), that is when either is high you want the EPROM to output on the data bus, so in positive logic OE = A15 | A14 ... unless you meant to say the the !OE signal should be LOW when A15|A14 that is when either is high.... I'm confused, maybe the 74LS02 actually does not need an inverter if it outputs !(A15|A14) as it is high only when they are both low -> I can connect it to the /OE directly as I want the EPROM to output on the bus when either is HIGH and do nothing only when both are LOW.

Edited May 5, 2014 by phoenixdownita

[phoenixdownita]

Turns out I don't need an inverter, yeahh!!!

 

The multi is not yet ready but I managed to do a quick test replacing the ROM with a 27C512 and it all worked.

If I would have read with more attention http://www.atarihq.com/danb/7800cart/C100339.shtml

I would have seen that it states 512Kbit (48KByte) non banked CS low -> /OE -> no inverter.

 

I guess I am not familiar with the notation !OE = A15|A14 which if I recollect comes from PAL programming, once more thanks for the hint, kind of set the expectations.

 

In any case nice to know that it's less involved than for 32K. I bet by ballooning the 32K games to 64K they would work just as fine on the supercart as I doubt any of them try to access 4000-7fff, and it's far easier to work on it because of the way power is routed.

 

I'll complete the multi for 48K games likely next week-end when I'll have time to build another mini perfboard for the switches and the pull-up resistors.

 

The complete list of titles is:

Desert Falcon

Donkey Kong

Donkey Kong Junior

Hatrick

Karateka

Mario Bros

One on One Basketball

Super Huey UH-IX

Edited May 5, 2014 by phoenixdownita