vgmrips

The forum about vgm files
It is currently 2023-02-02, 3:25:40

All times are UTC + 1 hour [ DST ]




Post new topic Reply to topic  [ 3 posts ] 
Author Message
PostPosted: 2022-03-04, 13:09:27 
Offline

Joined: 2020-03-05, 9:25:23
Posts: 24
In the Soldam_(Jaleco_Mega_System_1) pack, the following data blocks sequence can be found: 67 66 8b 08 00 00 80 00 00 04 00 00 00 00 00. What am I to make of the data size of 0x80000008? 8 of that is the subheader for the ROM write, leaving 0x80000000. This game appears to use 2 Oki M6295s, so I might hypothesize that the high bit means it's the ROM for the second chip, but that leaves me with a ROM data size of 0, which is clearly incorrect as data follows the ROM write subheader.


Top
 Profile  
 
 Post subject:
PostPosted: 2022-03-04, 13:58:17 

Staff Staff
Programmers Programmers
Musicians Musicians
Contributors Contributors
Reverse engineers Reverse engineers
Offline
User avatar

Joined: 2011-12-01, 20:20:07
Posts: 4362
Location: Germany
Data size 0x80000008 indeed means "size 0x08, 2nd chip". (I guess that I also forget to document this.)
The size includes the ROM header, which is 8 bytes and followed by the actual data that is to be loaded into the ROM space.

In this case, the data block has: data size 0x08, ROM size 0x40000, start offset 0x00, [no actual payload].
This effectively means that it will just allocate the 256 KB of ROM space for the second OKI chip and not fill it with any data.


Top
 Profile  
 
 Post subject:
PostPosted: 2022-03-04, 14:07:47 
Offline

Joined: 2020-03-05, 9:25:23
Posts: 24
Ah, I see. I thought there was ROM data following, as there was apparent 4-byte structures, but it looks like it's just repeats of 54 xx xx 7x which make sense for the chips the game uses..


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 3 posts ] 

All times are UTC + 1 hour [ DST ]


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
[ Time : 0.025s | 13 Queries | GZIP : On ]