SpritesMind.Net

[snkenjoi]

First, a little intro.

Some of you will recognise me from Sonic Retro, where I make hacks of the various sonic games. I recently made this 'demo' with stef's devkit that got me interested in spritesmind.

Anyway, I hope you find this an interesting read, it documents my journey to attempt to create the smallest Megadrive ROM that actually does something.

So, first I need some code that does something basic - this is to check that the code actually worked, and that it's relativly small.

The best thing I could think of for this task was to make the screen go green :) The code is a carbon copy from the checksum error routine from 'most' ROMs.

So here is the first revision, with the checksum code pasted after the header I ripped from Sonic 1.

[Shiru]

This is surely interesting information for 256/512b intro or minigame (1K/2K/4K) creators.

I think, relying for padding zeroes is somewhat wrong, because in the real world if you have, say, 256 byte ROM chip, it will not have zeroes above 256 byte. Instead, it will be repeated throughout whole address space.

[Chilly Willy]

Most of the exception vectors will never get called, so you could easily use most of that space for code. The rom header should probably be left alone, but you could also stick code or data in the strings of the header.

[HardWareMan]

Chinese programmers don't fill required header (except vectors table) and they games run only on chinese MD clones (without TMSS). So, to run your code on MD with TMSS you will need to fill only used vectors and string at $100..$103 (wich contains "SEGA" word, that presence checked by TMSS). All other places can be filled your own data/code.

[TascoDLX]

[TmEE co.(TM)]

and TascoDLX pwns everyone
_________________
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http://www.tmeeco.eu
Files of all broken links and images of mine are found here : http://www.tmeeco.eu/FileDen

[Chilly Willy]

That won't work on all Genesis models, so it doesn't count.

As stated in another post by HardWareMan, you at least need the "SEGA" in the header or TMSS systems won't accept it.

[TmEE co.(TM)]

so you have a 230 byte ROM with lot of nothingness in it
_________________
Mida sa loed ? Nagunii aru ei saa
http://www.tmeeco.eu
Files of all broken links and images of mine are found here : http://www.tmeeco.eu/FileDen

[Chilly Willy]

260

[TmEE co.(TM)]

craaap.... I somehow got 226 in my mind..... my brain needs sleep which it has not got for a while
_________________
Mida sa loed ? Nagunii aru ei saa
http://www.tmeeco.eu
Files of all broken links and images of mine are found here : http://www.tmeeco.eu/FileDen

[snkenjoi]

Chilly Willy; You didn't read this >:|

[Chilly Willy]

[snkenjoi]

Maybe it doesn't count in your eyes. That's fine.

But you're still missing the point. Thankfully you don't govern what I can and can't try to do :)

(Besides, it does do something... it detects if you have TMSS or not ;)

I'm not looking for praise, I'm saying "Hi guys, I joined the forum. Here's something cool I did recently that you may find interesting."

You don't have to be such an arse about it :(.

[Chilly Willy]

Sorry, but "loop: bra loop" demos are LAME, not interesting. You'd have a be a complete noob to think otherwise. Just telling it like it is.

And to tell the truth, when someone comes along gushing about how fantastic such things are, yes, I DO have to be an arse about it.

Feel free to share your "exciting" potty training stories, but don't get mad at me when I laugh and point.

[Shiru]

If you have real 256 byte ROM, word 'SEGA' probably could be placed at $000, but if it is possible to make the code start somehow after that? I don't know 68K opcodes, what 'SEGA' would be as code?