TIA Chip Question...for our programming folks

[StephenJ]

When playing my 2600, I have no problems with the sounds of the games. For me, they fit the graphics and are part of the charm of the system. I would never want that to change. However, when it comes to most of the 7800 games, that relay exclusively on the TIA chip, I feel there is a disconnect as far as graphics vs. sound. I wish there was an easy way to improve the sound quality of all of the 7800 games that rely on the TIA chip.

I know of the Pokey Chip, and its compatible games. But, this post is about the TIA chip and the games that have to use it.
I know next-to-nothing about computer programming and hardware, so please keep that in mind when reading my question. Here goes...Is it feasible to replace the TIA chip with a redesigned chip that works the same, but has higher quality sounds? I'm not saying that it would offer additional sounds, that could only be accessed by changing the code, rather it would use original game programs, but would output higher quality versions of the sounds. I suspect that it's far more complicated than that...but it's something I wanted to ask the AA programmers. Is something like that even possible?

 

All the best,

StephenJ

[CPUWIZ]

Anything is possible, if you have unlimited funds. For anyone here on AA, I am gonna say no.

[Jinks]

Go to a music shop and buy an effects processor and run your audio thru that.

You can thank me later..

[Tidus79001]

It makes me think of this. It is an accessory for the Sega Genesis that allows it to play Sega Master System games and has the capability to upgrade the sounds in the game by accessing per-existing code built into specific titles that support the enhanced audio

 

http://www.stoneagegamer.com/powerbase-mini-fm.html

 

The Sega Mark III released in Japan was the essentially the same as the Sega Master System in the US, but with the exception that the Mark III had a FM sound chip that offered better quality sound where as the Master System only had PSG sound that came across as somewhat weak or inferior and lacking depth. It was later found that many of the titles cross released to the US contained FM code was well as PSG code but at the time no one had any clue that this even existed in the ROM due have no way to access those sounds outside of using a Japanese Mark III console and had only ever heard the PSG sounds in the US released of the game. It wasn't until devices like the PowerBase FM / PowerBase FM Mini that US gamers were able to access the FM sounds and hear sounds in the games that they had never heard the likes of before. When the game boots up that contains FM code it is able to automatically upgrade the sound to FM if the code in the game detects the presence of the FM chip. US gamers were blown away hearing sounds that they had never heard before from games that they knew so very well.

Edited September 21, 2017 by Tidus79001

[EricBall]

Define "higher quality". The TIA (and POKEY for that matter) are simple LFSR based waveform generators. From a programming perspective there are three inputs for each of the two channels:

AUDF, a 5 bit divisor of 2 * the horizontal retrace frequency

AUDC, a 4 bit LFSR selector, which controls the AUDF frequency to waveform

AUDV, is a 4 bit volume control of the waveform output

 

The problem is these values are hard coded into the game ROM. So even if you added an extra bit into one of the registers, the games wouldn't be able to use it.

 

What you could do is tap the output TIA audio output pins (12 & 13) and put them through a high quality amplifier / filter. This will also expose some "stereo" effects in some games.

 

[StephenJ]

It makes me think of this. It is an accessory for the Sega Genesis that allows it to play Sega Master System games and has the capability to upgrade the sounds in the game by accessing per-existing code built into specific titles that support the enhanced audio

 

http://www.stoneagegamer.com/powerbase-mini-fm.html

 

The Sega Mark III released in Japan was the essentially the same as the Sega Master System in the US, but with the exception that the Mark III had a FM sound chip that offered better quality sound where as the Master System only had PSG sound that came across as somewhat weak or inferior and lacking depth. It was later found that many of the titles cross released to the US contained FM code was well as PSG code but at the time no one had any clue that this even existed in the ROM due have no way to access those sounds outside of using a Japanese Mark III console and had only ever heard the PSG sounds in the US released of the game. It wasn't until devices like the PowerBase FM / PowerBase FM Mini that US gamers were able to access the FM sounds and hear sounds in the games that they had never heard the likes of before. When the game boots up that contains FM code it is able to automatically upgrade the sound to FM if the code in the game detects the presence of the FM chip. US gamers were blown away hearing sounds that they had never heard before from games that they knew so very well.

 

Tidus79001,

Very interesting stuff indeed!

 

Thanks for taking the time to share the information,

StephenJ

[StephenJ]

Define "higher quality". The TIA (and POKEY for that matter) are simple LFSR based waveform generators. From a programming perspective there are three inputs for each of the two channels:

AUDF, a 5 bit divisor of 2 * the horizontal retrace frequency

AUDC, a 4 bit LFSR selector, which controls the AUDF frequency to waveform

AUDV, is a 4 bit volume control of the waveform output

 

The problem is these values are hard coded into the game ROM. So even if you added an extra bit into one of the registers, the games wouldn't be able to use it.

 

What you could do is tap the output TIA audio output pins (12 & 13) and put them through a high quality amplifier / filter. This will also expose some "stereo" effects in some games.

 

Ericball,

"...Define "higher quality"..."

In nontechnical speak...the sounds of a boom-box are "higher quality" than that of a transistor radio (i.e. smoother, more depth, crisp without being ear-piercing, richer lower frequencies, etc.). That's about the best I can do.

 

"...What you could do is tap the TIA output pins...put them through a high quality amplifier / filter...".

Sounds like a good idea...along the same line as Jinks' suggestion...

"...effects processor...run your audio thru that..."

 

But, my question was more in the way of the feasibility of improving the sound by replacing the TIA with an improved design.

You answered that question nicely with your comment "...these values are hard coded into the game ROM...if you added an extra bit into one of the registers, the games wouldn't be able to use it..."

Thanks!

StephenJ

[Jinks]

Actually some guy already sells a 7800 with a processor in it.

Plug it thru your home stereo with the bass cannon turned to 11 dude! High infidelity indeed!

[StephenJ]

Actually some guy already sells a 7800 with a processor in it.

Plug it thru your home stereo with the bass cannon turned to 11 dude! High infidelity indeed!

Jinks,

I'd like to hear it. If you come across any sound-files, or even you-tube videos...pass it on.

 

Thanks,

StephenJ

[Memblers]

There is another way, excuse me if sounds a little crazy (because it is). It wouldn't require a modification to the system, however you couldn't use the RF output for audio to your TV (you'd need a separate audio amp/speaker or use an A/V mod to the system). One could make a pass-through cartridge, and plug your normal Atari game into the other end of it. This cartridge would have it's own audio output, and the audio synthesizer of your choice. The cartridge would spy on the CPU bus (let's say with a small-ish FPGA), and react to TIA writes. You would have a table of every possible combination of writes the game could make to the TIA, and use this to handle every combination of output you want to replace this with. With this, I imagine maybe just making a new pitch table so you have the same LFSR synthesis, but with the tones being closer to musically in-tune frequencies. This is a lot of work, for minimal improvement. If you change it too much, what would sound good on one game, probably will sound terrible on another.

 

This meets the goal of requiring no modification to the games, but it is impossible to just look at the TIA writes alone and know the intent of the sound. To go further, the cartridge needs more intelligence. Inevitably, this becomes a thing where you'd have to make game-specific configurations. At this point you might as well also patch the ROM as a Game Genie does, then you can mute the TIA audio and not need the separate audio output anymore. I'm not saying this would be easy to make, just possible.

 

I didn't exactly come up with this just for this thread, I'm actually designing hardware that will have these kind of capabilities.. Not for the 7800 though (and I didn't have this exact type of audio patching in mind), but it's definitely an interesting system that could use a soundchip. I feel the same way about the TIA like you said in your first post, I love it in the 2600, but to me it's just like 7800 doesn't even have a sound chip. I've seen the thread about the HOKEY project, I don't know what chip it is exactly but it's probably similar in capability to what I'm working with.

 

Other than all that crazy hardware, I am working on my own game-music-inspired synth chip (which includes TIA and Lynx-type sounds), but now that I'm seeing that 7800 homebrew actually exists, I wonder if there would be any interest in bringing it to the Atari? But I suppose if the HOKEY turns out well, there won't be much room for another audio expansion.

Edited September 23, 2017 by Memblers

[toiletunes]

Go for it! The more audio chip options, the merrier.

[StephenJ]

There is another way, excuse me if sounds a little crazy (because it is). It wouldn't require a modification to the system, however you couldn't use the RF output for audio to your TV (you'd need a separate audio amp/speaker or use an A/V mod to the system). One could make a pass-through cartridge, and plug your normal Atari game into the other end of it. This cartridge would have it's own audio output, and the audio synthesizer of your choice. The cartridge would spy on the CPU bus (let's say with a small-ish FPGA), and react to TIA writes. You would have a table of every possible combination of writes the game could make to the TIA, and use this to handle every combination of output you want to replace this with. With this, I imagine maybe just making a new pitch table so you have the same LFSR synthesis, but with the tones being closer to musically in-tune frequencies. This is a lot of work, for minimal improvement. If you change it too much, what would sound good on one game, probably will sound terrible on another.

 

This meets the goal of requiring no modification to the games, but it is impossible to just look at the TIA writes alone and know the intent of the sound. To go further, the cartridge needs more intelligence. Inevitably, this becomes a thing where you'd have to make game-specific configurations. At this point you might as well also patch the ROM as a Game Genie does, then you can mute the TIA audio and not need the separate audio output anymore. I'm not saying this would be easy to make, just possible.

 

I didn't exactly come up with this just for this thread, I'm actually designing hardware that will have these kind of capabilities.. Not for the 7800 though (and I didn't have this exact type of audio patching in mind), but it's definitely an interesting system that could use a soundchip. I feel the same way about the TIA like you said in your first post, I love it in the 2600, but to me it's just like 7800 doesn't even have a sound chip. I've seen the thread about the HOKEY project, I don't know what chip it is exactly but it's probably similar in capability to what I'm working with.

 

Other than all that crazy hardware, I am working on my own game-music-inspired synth chip (which includes TIA and Lynx-type sounds), but now that I'm seeing that 7800 homebrew actually exists, I wonder if there would be any interest in bringing it to the Atari? But I suppose if the HOKEY turns out well, there won't be much room for another audio expansion.

 

And the interesting stuff just keeps on comin'!...so glad I started this thread.

Thanks Memblers for chiming in and sharing your creative projects. I don't thing any of it sounds crazy at all.

 

StephenJ