Gradius 2 FC - VRC4 questions

[satoshi_matrix]

Hey all, I'm writing a review of one of the Famicom's best shooters, Gradius 2 and would like to put in the details of how the game was achieved. I know the game uses mapper 25, the Konami VRC4 but I don't really know much about it except that like the MMC2 mapper 9 was used only for Punch-Out, VRC4 is exclusive to Gradius 2.

Can someone here explain to me what the chip allowed and why it was needed for Gradius II? I'm also interested to know if Gradius II could be ported to a more common mapper like Contra was for a possible NES reproduction.

Also, is the VRC4 related to the VRC6 in Akujamou Densetsu and VRC7 in Lagrange Point? If so, what game used VRC5 and what did that chip allow?

Thanks.

[Jedi Master Baiter]

The VRC4... the most probable reason why Gradius II never made it here, I believe, was also used for one of the Wai Wai World games.

As for what exactly the VRC4 is & what it does:

-it is an ASIC mapper (custom-built integrated circuit); ASIC mappers can offer custom nametable mirroring, extra sound channels, & IRQ counters
-it is an upgrade to the VRC2, allowing the option to swap PRG at $C000 instead of $8000, among other things, which I don't care to understand.

There was this effort to hack Gradius II to run on an MMC3/MMC5 mapper a few years back.

I have no idea what the deal is with VRC5. .  And, as far as I know, the only relation that VRC6/7 have with 4 is that they're both by Konami.

You'll probably get better answers from NESDev... yeah, I see you already posted there, now. Great! I wasted my time.

[satoshi_matrix]

most of that is lost on me. the question is basically does the VRC4 do something say the MMC3 wouldn't and does Gradius II FC as complex as it is due to the VRC4 chip or just good konami programming? Many of the later bosses have such smooth animation, the game allows four options at once theres no slowdown and sprite flickering is kept at a minimum. I just played through the whole game tonight and as far as I can tell, its a real techincal achievement on the Famicom. Does the VRC4 allow sprites to be large like the MMC2 does or something special like that?

[UglyJoe]

most of that is lost on me. the question is basically does the VRC4 do something say the MMC3 wouldn't and does Gradius II FC as complex as it is due to the VRC4 chip or just good konami programming? Many of the later bosses have such smooth animation, the game allows four options at once theres no slowdown and sprite flickering is kept at a minimum.

Both chips (VRC4 and MMC3) are pretty powerful.  I'd guess you'd be able to pull off something like Gradius II with an MMC3.  The smooth animations are probably due to the low CHR-RAM bank sizes, which allowed them to swap in new graphics in a more precise manner.  The no-flicker part of it is probably due to good programming.  VRC4 has some IRQ features that I don't understand, so I guess those may have helped with that as well (but I really don't know).

I just played through the whole game tonight and as far as I can tell, its a real techincal achievement on the Famicom. Does the VRC4 allow sprites to be large like the MMC2 does or something special like that?

I don't think there's anything speical about the MMC2 that allows for large sprites.  The thing about Punch-Out is that it never really had more than two objects moving at once...

[Jedi Master Baiter]

I think you'd have a better understanding if you opened the game up in an emulator that has a PPU Viewer, like FCEUXD SP & play the game with it open.

[vgthing]

the game allows four options at once theres no slowdown and sprite flickering is kept at a minimum.

I have a hack of the original Gradius that allows you to have four options and a laser more akin to the arcade version. There is no more slowdown or flickering than the original version. I don't know why Konami didn't give us four options in the first place... I'd upload the rom, but I'm not sure if that's allowed.

EDIT: Thanks UglyJoe. PM me if you really want it, I guess.

[UglyJoe]

No rom uploads.  IPS patches are ok.  Or do whatever you want via PMs.

[homogenized]

Did you try the hack on an actual console?  If not, did you turn on simulation of the system's sprite limit and other limits on the emulator you were using to compare?

[satoshi_matrix]

I played it on the Powerpak and it seems there's no problem with the hack at all from what I saw. It's an improvement in every way.