GBA games on DS: Legacy GB sound channels

Discussion in 'NDS - Console and Game Discussions' started by Xan0906, Feb 1, 2014.

  1. Xan0906

    Xan0906 Newbie

    Jan 9, 2014
    My guess is that, since the DS lacks the GBC CPU, those channels are emulated on one of the DS processors while playing GBA games. Presumably it's also an issue for GBA ports on the DS, like the Mega Man Zero collection.

    Originally I thought this would impact sound quality on GBA games that use these channels, but I did a comparison recently and found the difference to be not really noticeable. Is there any information on how these legacy channels are performed on the DS?
  2. Ozito

    Ozito Not a new member anymore

    Mar 20, 2006
    I beg your pardon for my ignorance, but what does the gbc cpu have to do with gba games?
  3. Jayro

    Jayro MediCat USB and Mini Windows 10 Developer

    GBAtemp Patron
    Jayro is a Patron of GBAtemp and is helping us stay independent!

    Our Patreon
    Jul 23, 2012
    United States
    Octo Canyon
    The DS and DS Lite can play GBA games, and only GB/GBC through emulation.
  4. Foxi4

    Foxi4 On the hunt...

    pip Reporter
    Sep 13, 2009
    Gaming Grotto
    The two posters above don't seem to be familiar with the matter so I'll elaborate. The Game Boy/Game Boy Colour were both powered by a custom Z80-like CPU called Sharp LR35902. This processor was later implemented in the GBA for the sake of backwards compatibility as well as an additional sound coprocessor in GBA Mode, used to generate legacy 8-bit sound.

    This is just an assumption of mine, but I believe that if it's at all supported, it's probably emulated on one of the ARM cores or one of the chips offers equivalent functionality and as such the chip was completely skipped.

    I just had a look at GBATek but I'm afraid that there's no information about LR35902 or Z80 on there in the DS section, leading me to believe that its functionality either has been skipped or it's performed by the ARM7 natively.
    Ozito likes this.
  5. bobmcjr

    bobmcjr GBAtemp Advanced Fan

    Apr 26, 2013
    United States
    The NDS Phat/Lite appears to contain the GBA sound hardware, meaning that both PCM channels (A and B) as well as the analogue "chippy" 8-bit-like channels are included. The "chippy" channels are just coincidentally backwards compatible with GB/C games, but are primarily part of the GBA's sound chip. The Z80 CPU appears to have nothing to do with this. For more info see here:

    Edit: could be wrong, this is mainly based on what I understood from that link.
    Foxi4 likes this.
  6. Foxi4

    Foxi4 On the hunt...

    pip Reporter
    Sep 13, 2009
    Gaming Grotto
    Yeah, that's pretty much what I gathered as well.
  7. nl255

    nl255 GBAtemp Addict

    Apr 9, 2004
    Simply put, when the GBA came out it had GBC hardware in it for backwards compatibility. Thus some game developers took advantage of it and use the GBC sound hardware in their GBA games. So when the DS came out they had to either keep the GBC sound hardware or emulate it otherwise quite a few GBA games would not work on the DS and Nintendo didn't want to do like MS did with the 360 XB1 emulation where only a small percentage of older games would work.
    Ozito likes this.
  8. BORTZ

    BORTZ Don't pretend you aren't impressed

    Dec 2, 2007
    United States
    Oh weird I never thought about that before. So GBA devs had access to the stuff in GBC mode. But the DS doesnt have access to GBA stuff in DS mode right? Why is that?