[Sonic 65]

Master Emerald, on Dec 12 2008, 02:37 PM, said:

I've never see this topic before so I think I'll finally find an answer for this.

The 2P mode in Sonic 2 features 2 stretched screens of the normal gameplay, but, I heard Mega Drive has no scaling capabilities. How can that exist so?

I don't know the exact details, but I know that it uses the Genesis's double-resolution mode (this is enabled by setting bits 1 and 2 of VDP register $C). I think Nemesis made a post about this a while back.

[Alriightyman]

Master Emerald, on Dec 12 2008, 02:37 PM, said:

I've never see this topic before so I think I'll finally find an answer for this.

The 2P mode in Sonic 2 features 2 stretched screens of the normal gameplay, but, I heard Mega Drive has no scaling capabilities. How can that exist so?

Jman explain it a bit here.

[Dann Woolf]

So I loaded a clean Sonic 1 ROM (it was a .gen file if that matters) into the editor and edited the first act of GHZ a bit. When I opened the edited rom in GENS all I got was a red screen. What did I do wrong and how do I fix this?

[Afti]

Your checksum is bad.

You click the 'Fix Checksum' option.

It's very simple.

[nineko]

I seriously think we should bring this topic back to a place where it can be seen even by people who don't bother to search the forum. Unless keeping it hidden is part of a plan to find out lazy people. But I doubt so.

[Dann Woolf]

Insanity, on Dec 12 2008, 11:00 PM, said:

Your checksum is bad.

You click the 'Fix Checksum' option.

It's very simple.

Ah, thanks. I'm kind of new at this. I know I should be starting with SonED but I hate the way it saves with project files. Plus I'm skipping the "oh shits I needs moar power" bit.

[Tweaker]

nineko, on Dec 12 2008, 04:02 PM, said:

I seriously think we should bring this topic back to a place where it can be seen even by people who don't bother to search the forum. Unless keeping it hidden is part of a plan to find out lazy people. But I doubt so.

Dear christ, get your head out of your ass already.

That said, the forum description says to read this forum and the archive below, which clearly had the answer to your question. There's a difference between confusion and laziness. Put a little effort into finding out the answer to a question before asking it—use the search function.

[muteKi]

Alriightyman, on Dec 12 2008, 02:54 PM, said:

Master Emerald, on Dec 12 2008, 02:37 PM, said:

I've never see this topic before so I think I'll finally find an answer for this.

The 2P mode in Sonic 2 features 2 stretched screens of the normal gameplay, but, I heard Mega Drive has no scaling capabilities. How can that exist so?

Jman explain it a bit here.

Also the Genesis DOES have "scaling" capabilities through the use of raster (I.e., line by line refreshing) effects. This is only possible for the non-sprite layers (I.e., the foreground and background), and isn't directly hardware related; it requires programming "tricks" in order to work. (Should be noted that similar effects can be done by writing to CRAM (color pallette) during line refreshes as well, theoretically allowing the entire color range of the MD on screen at once, though it's generally best used in modes where the screen is divided into horizontal sections as the normal palette restrictions still apply.)

[Twilight]

What does

align macro
cnop 0,/1
endm

mean? And what makes

move a6,usp

improper?

This post has been edited by Twilight: 12 December 2008 - 06:55 PM

[Irixion]

Uhh...what game? Sonic 1 or 2?

[Twilight]

Sonic 1.

[nineko]

Twilight, on Dec 13 2008, 12:50 AM, said:

What does

align macro
cnop 0,/1
endm

mean?

ASM68K doesn't support the "align" directive natively, which is used to align some stuff (code, but more usually data) at a certain offset in the rom. This is useful for example to put sound banks in specific locations or something.
So with this macro, which is defined at the beginning of the ASM file, you're making your ASM68K able to use the "align" directive, even if in a bastardized way.
Some other assemblers, like AS (iirc) does not need this macro, as they natively support align.

[FraGag]

To complement nineko's post...

Twilight, on Dec 12 2008, 06:50 PM, said:

And what makes

move a6,usp

improper?

I suppose that ASM68k incorrectly assumes that MOVE, without an explicit size attribute, is a word-sized operation. However, the documentation clearly states that MOVE to USP (usp is the user stack pointer) is a long-sized operation. This is, I think, a small bug in the assembler, as other assemblers accept it just fine, but can be worked around by replacing move with move.l, as has been stated in the guide on the wiki (SCHG How-to:Convert the Hivebrain 2005 disassembly to ASM68K).

[Anthall]

OK, Its another question from me about ASM, but I doubt this is possible, but I'd thought I'd ask.

Is it possible to create random subroutine jumping in Assembly for Sonic 1?

For example, is it possible to make some code so that there is a 50% chance of jumping to one Subroutine and a 50% chance of jumping to another subroutine?

Thanks.

EDIT: Fixed Crappy Grammar

This post has been edited by Anthall: 20 December 2008 - 09:46 AM

[Malevolence]

Anthall, on Dec 18 2008, 03:34 PM, said:

OK, Its another question from me about ASM, but I doubt this is possible, but I'd thought I'd ask.

Is it possible to create a random jumping in Assembly for Sonic 1?

For example, is it possible to make some code so that there is a 50% chance of jumping to one Subroutine and a 50% chance of jumping to another subroutine?

Thanks.

Anthall

Syntax Highlighted Code: ASM

	[color= #00bfff;]jsr[/color]	RandomNumber

	[color= #00bfff;]andi[/color].[color= #00bfff;]b[/color]	[color= #ff0000;]#[/color][color= #ff0000;]1[/color],d0

	[color= #00bfff;]tst[/color].[color= #00bfff;]b[/color]	d0

	[color= #00bfff;]beq[/color].[color= #00bfff;]s[/color]	Routine

	[color= #00bfff;]bra[/color].[color= #00bfff;]s[/color]	OtherRoutine

I believe that should work.

This post has been edited by Malevolence: 18 December 2008 - 03:55 PM