It is currently Mon Sep 16, 2019 1:30 am

All times are UTC - 7 hours





Post new topic Reply to topic  [ 36 posts ]  Go to page Previous  1, 2, 3
Author Message
 Post subject: Re: VRC5
PostPosted: Mon Sep 09, 2019 1:45 pm 
Offline

Joined: Sun Apr 13, 2008 11:12 am
Posts: 8557
Location: Seattle
Since bitmap fonts are not copyrightable under US law, I figured I'd convert the entire CHR ROM to an image for casual inspection:


Attachments:
Qta-tiles.png
Qta-tiles.png [ 80.38 KiB | Viewed 318 times ]
Top
 Profile  
 
 Post subject: Re: VRC5
PostPosted: Tue Sep 10, 2019 12:40 am 
Offline

Joined: Thu May 19, 2005 11:30 am
Posts: 975
So, should a NES 2.0 Mapper 547 file contain the 256 KiB CHR-ROM as it appears to the NES PPU, similar to Sanchez' UNIF file, or the 128 KiB content of the CHR-ROM as deduced in this thread? How confident can we be in this deduction? Ideally, somebody would desolder that CHR-ROM IC and read it with an EPROM programmer for verification. But that may not be feasible.


Top
 Profile  
 
 Post subject: Re: VRC5
PostPosted: Tue Sep 10, 2019 11:18 am 
Offline

Joined: Sun Apr 13, 2008 11:12 am
Posts: 8557
Location: Seattle
The easy questions: Is there really only 128 KiB of data? Definitely. Is PPU A3 ignored by the ROM? Definitely.

Meanwhile, we've encountered some number of other games with scrambled address lines, although in the past it's been for ease of routing. I don't see any particular value in de-shuffling the address lines to accurately represent the exact contents of the ROM: this isn't MAME.

Finally, the padding. I'd suggest this is something best addressed as what involves the leastbest performance and/or least maintenance load to an emulator author. (Perhaps the "right" thing for an emulator is to pre-expand the 128KiB of data to 512KiB during the loader, and just treat the 128s bit of QTRAM as another banking bit)


Last edited by lidnariq on Tue Sep 10, 2019 9:44 pm, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: VRC5
PostPosted: Tue Sep 10, 2019 2:50 pm 
Offline

Joined: Thu Oct 13, 2005 10:39 am
Posts: 72
definitely, the CHR rom on the QTA adaptor might be 128K and contain only a 1bpp fonts. but since I dumped them via ppu window I haven't realized it. now I have it emulated like a 256K rom with the least half isn't used at all (since the highest bits are ppu generated).

so my dumps may be threated as "overdumps" somehow now... this is easy to fix roms from 256 to 128k and adjust the emulation but dumps already released as is ;)


Top
 Profile  
 
 Post subject: Re: VRC5
PostPosted: Thu Sep 12, 2019 11:26 am 
Offline

Joined: Thu May 19, 2005 11:30 am
Posts: 975
lidnariq wrote:
I don't see any particular value in de-shuffling the address lines to accurately represent the exact contents of the ROM: this isn't MAME.
Generally, I tend to fall down on the MAME side of the argument, namely, that the exact contents of a ROM should be accurately represented, unless there is a compelling reason not to. In the case of Konami Q-Tai, when processing a 128 KiB CHR-ROM to add the second bitplane, a few additional shift operations more or less won't hurt. I would not like defining a 128 KiB CHR-ROM representation as canonical that is 1bpp but does not have the A0/A4 reordering, since such a representation exists neither for the PPU nor in the ROM chip.

CaH4e3 wrote:
but dumps already released as is
UNIF-format dumps are released; no NES 2.0 dumps are. It would not be the first mapper where the iNES/NES 2.0 representation differs substantially from the UNIF one (Supervision 16-in-1 is another one that comes to my mind).

How about this: Canonically define UNIF Mapper "KONAMI-QTAI" as using the 256 KiB CHR-ROM representation, and canonically define NES 2.0 Mapper 547 as using the 128 KiB shuffled CHR-ROM representation. Add that these canonical definitions shall not preclude emulators from accepting either representation when loading from either file format, by querying the CHR-ROM size, similar to the source code part I posted before.


Top
 Profile  
 
 Post subject: Re: VRC5
PostPosted: Fri Sep 13, 2019 12:39 am 
Offline

Joined: Sun Mar 19, 2006 9:44 pm
Posts: 1005
Location: Japan
A little reminder that "Q-TAI" is an incorrect transcription.

_________________
http://www.chrismcovell.com


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 36 posts ]  Go to page Previous  1, 2, 3

All times are UTC - 7 hours


Who is online

Users browsing this forum: No registered users and 2 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