PSIV item drop frequency?

[etony33]

Does anyone know what the odds are that an enemy will drop a certain item in PSIV (e.g. SHADOWSABR/SHDW BLADE, DARK RIDER/MOONSLASHR, CHAOSBRNGR/DEFEAT AXE)? If so, it'd be really handy to know.

[etony33]

Also, does anyone know what the odds are that Shir will steal SOMETHING? I know the approximate odds that she'll steal each item, and I'm guessing that her odds of stealing are either 32/256 (1/8) or 16/256 (1/16), but that's just an educated guess with nothing to back it up other than an approximation based on my experience.

[Snorb]

From what I've seen online, Shir has more or less (this is an early Sega Genesis RPG we're talking about, so I might emphasize "less") a 12.5% chance of stealing something when you take her to a shop.

Also, it is a really bad idea to make her steal something on Dezolis.

[etony33]

Well, I would imagine it is done the same way that random chance is done in any other game. The game generates random numbers between 00 (0) and FF (255). Sixteen of these random numbers mean Shir steals.

[Tryphon]

You are right.

I think I've identified the code that determines if and what Shir steal. Here it is :

Code: Select all

ROM:0000D096                 bsr.w   random_number ; d0 = random number between 00 and FF
ROM:0000D09A                 andi.w  #$F,d0
ROM:0000D09E                 bne.s   locret_0_D078 ; only values 00 to 0F do something
ROM:0000D0A0                 bsr.w   random_number
ROM:0000D0A4                 andi.w  #7,d0
ROM:0000D0A8                 add.w   d0,d2 ; the item belongs to a list of 8 items
ROM:0000D0AA                 move.b  unk_0_D0E8(pc,d2.w),(current_item_id).w



[BenoitRen]

So it gets a random number between 00 and FF, and if it's between 00 to 0F, the game does something with it. Those are 16 values that do something, the list of items is only 8 entries long?

[Tryphon]

There are 4 lists of 8 bytes (starting at 0xD0AA). I suppose d2 contains at this stage an id of the 'shop' you are exiting from.

The lasr list contain 8 times the value 7D, which corresponds to Visiphone. WHAT SHOP COULD IT BE ????

All of that is a guess, I didn't make any test (I'm looking for a way to enlarge windows).

[etony33]

Hmmm...I've never seen Shir steal any more than four separate items from each shop (Dagger, Laser Shot, Laser Knife, Fire Rod from Weapon Shop, Trimate, Hidapipe, Star Mist, Moon Dew from Item Shop, etc). Or is it something like Dagger listed three times, Laser Shot twice, Laser Knife twice, Fire Rod once? I'll have to check it out.

And this confirms my theory that Shir's level has no bearing whatsoever on what she steals and how often she steals it.

EDIT: I see how it works. It goes like this:

Weapon shop:
Dagger=50%
Lasr Knife=25%
LasrCannon=12.5%
Fire Staff=12.5%

Armor shop:
SilverCrwn=50%
Jewel Crwn=25%
Gr Sleeves=12.5%
Shuneboots=12.5%

Item shop:
Trimate=50%
Hidapipe=25%
Star Mist=12.5%
Moon Dew=12.5%

So if you have a 1/16 chance of stealing, and a 1/8 chance of getting a Star Mist, your odds would be 1/128 of having Shir steal a Star Mist every time you walk into an item shop. So if you can walk in and out, on average, 4-5 times per minute (accounting for the time it takes to walk from the item shop in Paseo to Rolf's house), and you want 10 Star Mists to bring to Noah, it'll take somewhere between 4 hr, 16 min and 5 hr, 20 min.

At least now I have an idea of how long it's SUPPOSED to take when I do that (although, because of the way probability works, you are by no means guaranteed to have even close to 10 Star Mists after 5 hours - or you could wrap it up in 30 minutes).

[Snorb]

Tryphon: The Visiphone's what Shir steals from Central Tower's Baggage Room.

Shir: (her loot bag is full of Star Mists and Moon Dews) They don't even sell these on Motavia. XD

[etony33]

Tryphon: The Visiphone's what Shir steals from Central Tower's Baggage Room.

I'm pretty sure he was being sarcastic.

Shir: (her loot bag is full of Star Mists and Moon Dews) They don't even sell these on Motavia. XD

Yeah, no kidding. For that matter, they don't sell them ANYWHERE. Nor do they sell a lot of those items anywhere, like Fire Staff and Gr Sleeves.

[Tryphon]

I don't know if the word 'sarcastic' has the same meaning than in French. If so, I didn't intend to be rude (and yes, I knew it).

As for Shir's level, I didn't copy the whole routine, but it checks if Shir has passed level 10. It could be interesting (and quite easy) to hack it so as her chances to steal increase with her level.

[etony33]

Rude? No, it doesn't mean rude. Maybe "facetious" would be a better description.

[Tryphon]

Ok. In French, it doesn't mean rude but it has the nuance of 'mocking' (but not quite, hard to explain).

[etony33]

Well, it CAN mean that in English as well...it depends on context, I guess. In this case, it's just you saying "hmm, I wonder what it could be" when the answer is obvious to everyone (well, everyone who has played the game, at least). That's why facetious would fit better.

[Tryphon]

I support facetious