Extended audio in Jaleco SS88006 - Mapper 18 ??

sdm · Post by **sdm** » Tue Apr 08, 2008 6:03 am

Why Jaleco SS88006 cartridges have AUDIO connector pins connected to controller?? Maybe SS88006 contain sound chip, but its never use by any games?

indaman · Post by **indaman** » Tue Apr 08, 2008 7:17 am

Interesting.

But i never heard about this Jaleco mapper.

And nothing on the internet talks about it.

Maybe Jaleco wanted to add extra audio on their SS88006 but didn't and it's only a remain of their old project.

NotTheCommonDose · Post by **NotTheCommonDose** » Tue Apr 08, 2008 1:49 pm

Too weird for me. They probably didn't use it because the NES had no extra sound capabilities.

BootGod · Post by **BootGod** » Tue Apr 08, 2008 2:19 pm

That extra chip slot marked 'IC4' is used for the D7756 sound chip used in some other Jaleco games such as Moe Pro! '90 and Shin Moero!! Pro Yakyuu

sdm · Post by **sdm** » Wed Apr 09, 2008 3:14 pm

NotTheCommonDose wrote:Too weird for me. They probably didn't use it because the NES had no extra sound capabilities.

This is Famicom cart, not NES.

BootGod wrote:That extra chip slot marked 'IC4' is used for the D7756 sound chip used in some other Jaleco games such as Moe Pro! '90 and Shin Moero!! Pro Yakyuu

hmm.. Something like ANALOG SOUND FILTER, not SOUND CHIP.

NotTheCommonDose · Post by **NotTheCommonDose** » Wed Apr 09, 2008 6:55 pm

My mistake.

BootGod · Post by **BootGod** » Thu Apr 10, 2008 3:17 pm

sdm wrote:hmm.. Something like ANALOG SOUND FILTER, not SOUND CHIP.

I'm not sure I'm understanding what you mean by that, but the D7756 is a sound / speech chip, not a sound filter. It has a built-in ROM storing ADPCM compressed sound samples, which unfortunately you can not directly access, unless it happens to be the type with an OTP EPROM instead. I have a datasheet on it here.

sdm · Post by **sdm** » Wed Apr 16, 2008 1:35 pm

ok. thanks for info.
I get Shin Moero!! Pro Yakyuu cart, and i record sound directly from D7756 chip:
http://www.speedyshare.com/255632160.html (WAV 700kb)

NotTheCommonDose · Post by **NotTheCommonDose** » Wed Apr 16, 2008 4:35 pm

How do you access this in the game itself? I wounder what other games use this chip? I wish this was an actuall sound expansion chip called the
"Jaleco SS88006"

sdm · Post by **sdm** » Thu Apr 17, 2008 2:15 am

I'm wonder why Jaleco used this chip? NES/FC sound chip have DPCM channel for PCM samples

Post by **tepples** » Thu Apr 17, 2008 7:43 am

sdm wrote:I'm wonder why Jaleco used this chip? NES/FC sound chip have DPCM channel for PCM samples

If you're using a lot of PCM, you generally want to put it in a separately switchable bank so that you don't need to freeze the game while it plays. From the perspective of the DPCM channel, there are three kinds of cartridge hardware:

Boards that hardwire $C000-$FFFF, such as UNROM (Blades of Steel). To play waves outside the fixed bank, the program needs to stop everything and write to $4011 with timed code. Some games on more capable boards do this anyway to use more efficient codecs than 1-bit delta modulation (e.g. Big Bird's Hide and Speak, The Three Stooges).
Boards that allow $C000-$FFFF to be switched, such as S*ROM, and boards that switch 32 KiB, such as A*ROM, B*ROM, G*ROM, and Color Dreams. Here, the DPCM area is switchable, but the code that runs during playback can't read another bank. The first two Bases Loaded games (USA equivalent of Moero!! Pro Yakyuu) used SFROM and SL3ROM.
Boards that allow $C000-$DFFF and at least one other 8 KiB bank to be switched, such as T*ROM and some Sunsoft boards. Here, the code can switch a wave into $C000-$DFFF while reading other kinds of data from $A000-$BFFF. These came along later, and Bases Loaded 3 and 4 used TLROM.

(For the sake of simplicity, I'm ignoring the possibility of playing through the vectors and wrapping around to $8000.)