It is currently Thu Oct 19, 2017 3:08 pm

All times are UTC - 7 hours





Post new topic Reply to topic  [ 8 posts ] 
Author Message
 Post subject: confirmation on real NES
PostPosted: Sun Jul 03, 2005 8:05 pm 
Offline
User avatar

Joined: Thu Mar 24, 2005 3:17 pm
Posts: 355
Could anyone test this on a real NES, to confirm the glitchy behaviour ? I've tested these glitches with several emulators. Perhaps others could post specific game glitches that look like emulator glitches too.

1: Rad Racer: when you go off the road, some scanlines will shift, causing parts of the road to be misplaced.

2: Battletoads vs Double Dragon: in the 2nd level, just before going into the elevator, and just after you get out the elevator, the upper part of the screen (the slower-scrolling part) will suddenly be misplaced.

An off-topic note about Battletoads and Battletoads vs DD: emulation of DMC cycle-eating, or even sound at all, is unnecessary for these to work correctly. They're running perfect (minus glitch 2 ;p ) here after synchronising CPU<->PPU.

3: Fine X behaviour: This can be tested in Double Dragon II, and Super Mario Bros 3, maybe others.
Double Dragon II: the bottom scanline, above the statusbar, will scroll wrongly.
Super Mario Bros 3: after the 2nd level, enter the bonus round (the one with scrolling mushroom/flower/star). Press the button to make the top bar stop, and now the bottom line of this bar will scroll wrongly. It will also happen at the 2nd bar.

I've currently fixed that, by resetting fine X scroll while resetting address tile X. This seems logical to me.


*edit*
AFAIK already tested and confirmed:
Megaman 3: on the boss select screen, the scanline above shadow man looks wrong.
Crystalis: the scanline above the statusbar and above textboxes looks wrong.


Top
 Profile  
 
 Post subject:
PostPosted: Sun Jul 03, 2005 8:58 pm 
Offline
User avatar

Joined: Mon Sep 27, 2004 8:33 am
Posts: 3715
Location: Central Texas, USA
This is a great idea. I just added a "game bugs" page to the nesdev wiki. I recently wrote something similar up for buggy video game music files, to avoid chasing non-bugs.

Add them to the Wiki yourself or post them here and I can transcribe them after this thread has gathered several replies.


Top
 Profile  
 
 Post subject:
PostPosted: Sun Jul 03, 2005 10:56 pm 
Offline
User avatar

Joined: Sun Sep 19, 2004 10:59 pm
Posts: 1389
Quote:
Super Mario Bros 3: after the 2nd level, enter the bonus round (the one with scrolling mushroom/flower/star). Press the button to make the top bar stop, and now the bottom line of this bar will scroll wrongly. It will also happen at the 2nd bar.


This is confirmed to happen on the real hardware - modifications to the fine X-scroll value (bottom 3 bits of first write to $2005) take effect immediately while coarse scroll (upper 5 bits of first write to $2005) are only applied at the beginning of each scanline.

_________________
Quietust, QMT Productions
P.S. If you don't get this note, let me know and I'll write you another.


Top
 Profile  
 
 Post subject:
PostPosted: Sat Jul 09, 2005 7:01 am 
Offline
User avatar

Joined: Thu Mar 24, 2005 3:17 pm
Posts: 355
Quietust wrote:
This is confirmed to happen on the real hardware - modifications to the fine X-scroll value (bottom 3 bits of first write to $2005) take effect immediately while coarse scroll (upper 5 bits of first write to $2005) are only applied at the beginning of each scanline.


That's a pity, in a way. It also happens in Castlevania 3 (mist effect), Dragon Warrior 3 (sky in intro), World Grand Prix (in-game).

Another one. Commando (U), Senjou no Ookami (J):
- choppy scrolling
- disappearing sprites
- screen flickering with garbage
- visible screen redrawing

I was sure that Commando was a bad dump, until i noticed that the Japanese version behaves the same.


Top
 Profile  
 
 Post subject:
PostPosted: Tue Jul 12, 2005 1:16 pm 
Offline
User avatar

Joined: Thu Mar 24, 2005 3:17 pm
Posts: 355
About Rad Racer in an old thread:
http://nesdev.com/cgi-bin/wwwt ... =#Post1824

I think he's talking about the yellow scanline when going left. But not this, clarified with a pic:
Image
Only happens on the GoodNES (U) version, not the (E).
It can be fixed if you fiddle with the timing of hscroll reset, which I normally have timed at the same time Y is updated, cycle 251.

Nessie (if you're here), could you confirm ?


Top
 Profile  
 
 Post subject:
PostPosted: Wed Jul 13, 2005 12:31 pm 
Offline

Joined: Tue Nov 23, 2004 9:35 pm
Posts: 615
[quote]Another one. Commando (U), Senjou no Ookami (J):
- choppy scrolling
- disappearing sprites
- screen flickering with garbage
- visible screen redrawing

I was sure that Commando was a bad dump, until i noticed that the Japanese version behaves the same.[/quote]

I believe that Commando is supposed to play that way. That game was programmed very poorly and the large numbers of sprites don't help anything. Capcom hadn't quite mastered the NES yet.


Top
 Profile  
 
 Post subject:
PostPosted: Wed Jul 13, 2005 2:36 pm 
Offline
User avatar

Joined: Wed Nov 10, 2004 6:47 pm
Posts: 1845
hap wrote:
It can be fixed if you fiddle with the timing of hscroll reset, which I normally have timed at the same time Y is updated, cycle 251.



Other games like Battletoads will complain if you don't have H scroll reset and Y update done at the right time. I use the following times in Schpune and have had no related problems in any games I've tried:

Scroll Init (LoopyV = LoopyT) : Cycle 305 on scanline -1 (pre-render scanline)

H Scroll Increment (LoopyV += 1, wrap nametables at 32) : every 4th cycle in a set of 8 on every rendered scanline (4, 12, 20, 28, ... 252). As well as cycles 320, 328 on every rendered scanline and scanline -1 (for the first two tiles on the next scanline).

H scroll Reset (LoopyV refilled with bits 0x041F from LoopyT) : cycle 256 every rendered scanline

V scroll increment : cycle 252 of every rendered scanline

I would LOVE confirmation on any/all of these. Blarrg gave an approximate time of the scroll init (which came to be around cycle 300) -- I used his demo to fine-tune that to 305 for my emu. The other values I think I got from Hyde -- but dunno if he did anything other than trial and error to get Battletoads working *shrug*


Top
 Profile  
 
 Post subject:
PostPosted: Wed Jul 13, 2005 4:31 pm 
Offline
User avatar

Joined: Thu Mar 24, 2005 3:17 pm
Posts: 355
I've asked on another forum.

Commando:
"I never tried it in an emu, but if the "glitch" is characters flashing, that's normal."

Rad Racer:
(about the glitch on the above pic) "I finished it again a couple of months ago (back in january) and donエt remember seeing that. I was playing the NTSC version (USA made) of the game, on my PAL-M dual slotted NES . (I can confirm that by the weekend)."

(other glitch) "when you go far left off the road, sometimes thereエs this "off-road" line in the road (understood ? my phrasing sucks)probably a game glich."

(about the couple of pixels on the upper right part of the horizon) "i don´t recall seeing any gliches on the horizon, might be wrong though.."

PAL-M is basically the same as NTSC (525 lines, 60hz).

*edit* another one for Commando:
(she tested it in emulators to see what I meant) "Commando DOES seem pretty glitchy. I recall it being glitchy on an actual NES but... not as glitchy as it is, with EVERYTHING flickering, even the ground layer. Could be my faulty memory though. (Tested using nnnesterJe and VirtuaNES.)"


When fiddling with reset x timing, Battletoads doesn't have any problems here (no lockup at level 2), neither does its brother (Battletoads & DD). I've tried it as far as around cycle 321; just before the tile prefetches of the next scanline. (Y still at 251)


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 8 posts ] 

All times are UTC - 7 hours


Who is online

Users browsing this forum: Yodak and 7 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group