Some nes games check if more then 8k of SRAM was present and then display a copyright screen if it is determined if the rom is being played on a copy cart. Can someone please explain and give code on how i would check if more then 8k of SRAM is present due to a flash cart like the PowerPAK? I only want to allow my game to run on flash carts so thieves don't make repro carts of my game and sell it for $. I know this is not failproof but, atleast it provides some measure of protection from simple crooks.

If you're going to make it exclusively for the PowerPak, there might be some other things you can check for, since it contains so much mapper hardware.

You should probably talk to Bunnyboy about it.

design a custom mapper. that makes pretty good copy protection. still not perfect, but keeps average Joe from being able to dump your game.

Well, I think he specifically wants to release it for PowerPak use, but wants to prevent repro-makers from profiting.

Also, I'm pretty sure his game is already done, for the most part.

@arch 8ngel: No i haven't started my game yet, but want to add my copy protection code first, before i release any betas/demos.

@udisi: Alot easier said then done, i have no idea what so ever on how i would even begin trying to do that.

Sincerely,

Nes Open Tennis

really, I wouldn't even bother with copy protection for a homebrew. The market isn't that huge. If you sold 250 copies that would be a huge success. In reality I'd say 50-100 is normal. for that small of a run I think copy protection is more trouble than it's worth.

bunnyboy used a custom mapper for Gilder. it doesn't have to be all that complicated, and it doesn't take any rom space. it's all hardware. if you can make the custom mapper, then you could also make the mapper file for the powerpak.

You said it yourself that the ram check is far from foolproof, so is the mapper idea. Really, I'd worry more about the game than copy protection. Not worth the hassle.

I dont think you need a copy protection scheme but in either case, if you know of a title that has this SRAM detection, let us know and someone can run it in a debugger and deduce how it is done.

I think with FCEUX you can turn on tracing and actually generate source for any code that is excercised by the emulator.

Also, typically you can contact Leon or the other repro makers and ask them not to repro your games (I dont think they repro much homebrew anyways). Conversely, you can contact them and give them permission in which case they'll likely create their own versions of a label for it.

Al

You could check for powerpak by exploiting open bus. Altough it can technicly recreate open bus effects it doesnt as of writing. (and its doubtfull bunny will add it)

I'm pretty sure anyone who would take the effort to reproduce this for money would be able to hack/modify the rom to bypass the copy protection.

What exactly is the motivation here? If this game is good enough that someone would want to sell copies of it, why wouldn't you sell copies of it through retrozone? I'm sure you could work something out with bunnyboy where you could release say a "demo version" until you sell X amount through retrozone, then release the full rom.

I get what you are saying, you don't want someone else to profit from your work.However, people are willing to pay for your hard work. Why not embrace it?