Search found 81 matches

by Natsumi
Tue Jan 12, 2016 10:08 pm
Forum: Megadrive/Genesis
Topic: Pointer Tables and Jump Tables By Example
Replies: 12
Views: 3374

Re: Pointer Tables and Jump Tables By Example

Looking back at it, it indeed was a misinterpretation of the logic on my end. Sorry for the confusion
by Natsumi
Tue Jan 12, 2016 9:52 am
Forum: Megadrive/Genesis
Topic: Pointer Tables and Jump Tables By Example
Replies: 12
Views: 3374

Re: Pointer Tables and Jump Tables By Example

ok then, I'll tell you exactly why. First and foremost , there is no ' bsr (a0) ' in Motorola 68000. I am unsure of later models having it, but I highly doubt, just because 'jsr (a0)' already exists and is good enough way to do so. Second , ' move.l table_1(a0), a0 ' is terrible way to do anything. ...
by Natsumi
Tue Jan 12, 2016 7:35 am
Forum: Megadrive/Genesis
Topic: Pointer Tables and Jump Tables By Example
Replies: 12
Views: 3374

Re: Pointer Tables and Jump Tables By Example

if we are strictly on Motorola 68000, the example ehaliewicz gives is wholly useless, and even if you could use said instructions in practice, it still would lead to poor implementation. Instead, here is a 100% real world application of a jumptable, used by me in a program; moveq #0,d0 move.b CrashI...
by Natsumi
Wed Jan 06, 2016 11:35 am
Forum: Megadrive/Genesis
Topic: Are there any good/elaborate ASM tutorials around?
Replies: 11
Views: 3881

Re: Are there any good/elaborate ASM tutorials around?

here is also very basic tutorial for absolute newbies: http://mrjester.hapisan.com/04_MC68/
by Natsumi
Wed Dec 23, 2015 5:35 am
Forum: Megadrive/Genesis
Topic: Question on SRAM
Replies: 14
Views: 4571

Re: Queston on SRAM

I can tell just looking at it, the SRAM header is wrong. But fear not, as for most emulators this does not matter. This is also why the Fusion .srm file is usually only so large as you have written to it, rather than the intended size. There is no way to force this, other than to fill it completely....
by Natsumi
Sun Dec 20, 2015 3:09 pm
Forum: Megadrive/Genesis
Topic: VDP's strange internal unknown laws.
Replies: 11
Views: 2736

Re: VDP's strange internal unknown laws.

Could you explain a little more or perhaps show an example; anything you told and asked make no sense without proper context
by Natsumi
Thu Dec 03, 2015 9:09 pm
Forum: Megadrive/Genesis
Topic: Noob questions: is the ROM header actually required?
Replies: 14
Views: 2843

Re: Noob questions: is the ROM header actually required?

Sonic & Knuckles (and possibly Sonic 3, havent checked) have the first longword (stack address) set to 0. Later in the code it is corrected the be the actual stack address in RAM. And a hack I've made has text instead of the stack address. So yes, first longword is also not needed, because you can u...
by Natsumi
Thu Dec 03, 2015 2:39 am
Forum: Megadrive/Genesis
Topic: Noob questions: is the ROM header actually required?
Replies: 14
Views: 2843

Re: Noob questions: is the ROM header actually required?

most developers are sensible enough to have the games able to run on NTSC and PAL systems as is, even if they have region locking (Sonic 3 and Sonic & Knuckles for example are like this), however some specific games or game companies may have had different policies regarding to this and having separ...
by Natsumi
Wed Dec 02, 2015 1:59 pm
Forum: Megadrive/Genesis
Topic: Noob questions: is the ROM header actually required?
Replies: 14
Views: 2843

Re: Noob questions: is the ROM header actually required?

I have 3 Mega Drives. 2x EU Sega Mega Drive Model 1, and 1x US Sega Genesis model 1. I also have EU Sonic the Hedgehog, US Sonic the Hedgehog, EU Sonic the Hedgehog 2, JP Sonic the Hedgehog 2, and eu Sonic the Hedgehog 3. Now, I can play all the Sonic 1 and 2 carts on any Mega Drive I own (except th...
by Natsumi
Mon Nov 30, 2015 8:24 pm
Forum: Megadrive/Genesis
Topic: Noob questions: is the ROM header actually required?
Replies: 14
Views: 2843

Re: Noob questions: is the ROM header actually required?

I thought maybe at least the country codes at $1F0 ("J" for Japan, "U" for USA, etc.) might be needed by the hardware for region locking games, but it looks like that's not the case? Region locking is always software implementation. Such as the Sonic 3 and Sonic & Knuckles carts (I believe), check ...
by Natsumi
Mon Nov 30, 2015 5:14 pm
Forum: Megadrive/Genesis
Topic: Hello...
Replies: 16
Views: 3925

Re: Hello...

as far as emulators are concerned, my suggestion is to use Exodus if your PC is powerful enough, and if not, then Regen. Never test with Fusion or Gens as they are horribly inaccurate. Flashcart however, even if not 100% accurate is easily the best place to test on. As far as assemblers, I suggest u...
by Natsumi
Fri Nov 27, 2015 1:22 pm
Forum: Megadrive/Genesis
Topic: Noob questions: is the ROM header actually required?
Replies: 14
Views: 2843

Re: Noob questions: is the ROM header actually required?

only the pointer to start of code, and SEGA at $100 are required. Everything else depends on your needs. For example if you need V-int and H-int you will need their specific pointers, or if you want to be emulator friendly you probably would have the SRAM and ROM pointers as well, but by no means ar...
by Natsumi
Thu Nov 19, 2015 10:16 pm
Forum: Tools
Topic: New Mega Drive/Genesis compiler in the works!
Replies: 8
Views: 2238

Re: New Mega Drive/Genesis compiler in the works!

I hope when you release this, the asm output will be clean and reasonable. BEX, I believe, had a constant issue with nonsensical asm output, with code that was redundant, terrible and utterly unoptimized, or plain insane use of opcodes (such as addi.l #0,d0 as opposed to tst.l d0, or sub.l d0,d0 as ...
by Natsumi
Thu Nov 19, 2015 12:52 pm
Forum: Megadrive/Genesis
Topic: Artifacts of the direct color DMA
Replies: 4
Views: 1504

Re: Artifacts of the direct color DMA

ah sorry, misunderstood the post. In that case I dont know anything that'd help, and I doubt there is anything that would.
by Natsumi
Thu Nov 19, 2015 9:39 am
Forum: Megadrive/Genesis
Topic: Artifacts of the direct color DMA
Replies: 4
Views: 1504

Re: Artifacts of the direct color DMA

there is no way to "fix CRAM dots, but with clever timing you can avoid them. Sonic 3 is a great example of this; while it doesnt DMA, it writes 3 colours per scanline, with a very precise timing to basically push the dots into overscan. This and some clever code (in case of DMA) and you can squeeze...