Jump to content
Sign in to follow this  
Synthpopalooza

Other sound chips besides POKEY ... cheaper alternatives?

Recommended Posts

So I found this online.

 

https://www.newegg.com/p/2A3-0029-1NZH6?item=9SIA7PD7XY9091&source=googleshopping&nm_mc=knc-googlemkp-mobile&cm_mmc=knc-googlemkp-mobile-_-pla-utsource-_-ec+-+semiconductors-_-9SIA7PD7XY9091&gclid=CjwKCAjwzJjrBRBvEiwA867byhSJFnkdCltErTE5lendtVVynzXfrKbjSx6bu8Jaa4JLc3zB_wuDYxoC8xUQAvD_BwE&gclsrc=aw.ds

 

The AY-3-8910 was a popular sound chip that ended up being used in a lot of popular 80s arcade games (like Frogger and Congo Bongo), as well as Intellivision, MSX computers, Colecovision, and the Sega Maser System.  $4.98 a pop is VERY cheap.  You get 3 square waves and a noise generator.  Could this chip serve the 7800 as a cheap POKEY replacement?  Is it 6502 compatible?

 

  • Like 2

Share this post


Link to post
Share on other sites

The "Mockingboard", "Phasor" and "Arcade Board" are cards for the Apple ][ (6502-based) that have AY-8910 chips, so...yeah, it's 6502-compatible.

 

ColecoVision and Master System use SN76489, which is similar but not identical.

  • Like 1

Share this post


Link to post
Share on other sites
1 hour ago, Synthpopalooza said:

So I found this online.

 

https://www.newegg.com/p/2A3-0029-1NZH6?item=9SIA7PD7XY9091&source=googleshopping&nm_mc=knc-googlemkp-mobile&cm_mmc=knc-googlemkp-mobile-_-pla-utsource-_-ec+-+semiconductors-_-9SIA7PD7XY9091&gclid=CjwKCAjwzJjrBRBvEiwA867byhSJFnkdCltErTE5lendtVVynzXfrKbjSx6bu8Jaa4JLc3zB_wuDYxoC8xUQAvD_BwE&gclsrc=aw.ds

 

The AY-3-8910 was a popular sound chip that ended up being used in a lot of popular 80s arcade games (like Frogger and Congo Bongo), as well as Intellivision, MSX computers, Colecovision, and the Sega Maser System.  $4.98 a pop is VERY cheap.  You get 3 square waves and a noise generator.  Could this chip serve the 7800 as a cheap POKEY replacement?  Is it 6502 compatible?

 

I think this is an amazing alternative to Pokey, definitely second this!

Share this post


Link to post
Share on other sites

Apparently there are lots of clones of this chip too.  The only thing is, for development purposes we'd need a pass thru cart and/or the functionality of this chip added to emulation such as A7800.

Share this post


Link to post
Share on other sites

Considering the AY chips are so well documented, I can't imagine it being to challenging to implement it into an emulator, but that's coming from a newbie.

Share this post


Link to post
Share on other sites

Good to hear! I'm really behind this idea since I've been designing a homebrew for the 7800 for a while and was convinced that the AY-3-8910 was gonna be the sound chip of choice, since I do not wanna get stuck with just the TIA for sound, and I'm not a massive fan of salvaging pokey chips from donor carts.

Edited by R_Leo_1

Share this post


Link to post
Share on other sites

If what you are needing is genuine early 80's arcade quality sound, this is a good idea.  It doesn't have all of the POKEY features, but based on the arcade titles that use it, it is very capable.   There are no doubt other sound chips out there which work just as well too.

Share this post


Link to post
Share on other sites

Looks like the crowd is swinging toward the GI chip, but the SN76489 chip sounds mostly similar for quite a bit less money and needs a lot less support circuitry.

Just my $0.02...

  • Like 1

Share this post


Link to post
Share on other sites
1 hour ago, Synthpopalooza said:

There's also this:

 

http://www.actionpinball.com/parts.php?item=6808

 

This was the sound chip used in Williams Defender.  If it is 6502 compatible ... it is more pricey at $15 ... but if you are gonna port the arcade title to the 7800, might as well do it with the original arcade sounds too.  :)

The 6808 (and 6802), of course, are actually CPUs. The Williams sound board interfaced them to a DAC through a PIA -- quite a bit of hardware to consider stuffing into a 7800 cart! ;-)

Share this post


Link to post
Share on other sites
Quote

I have no idea on how common this chip is now, but it can be had for a couple bucks on ebay. According to the AY-3-8910 wikipedia page, clone chips are still being produced.

 

Is 3 voices a non-starter, and if so, do we need 2 chips on a cart? Who will build the new cart design? If someone builds it, will they come?

Quoted from your post in that thread ...

 

3 voices is definitely not a deal-breaker.  First of all, to get any meaningful music out of the POKEY without tuning errors, and keep the same frequency dynamic heard on arcade games or other systems, you generally have to sacrifice a channel anyway and use one of the 4 POKEY filters ... for example, the title music I did for Bentley Bear was done using only three channels of square wave $Ax, but combining channels 0 and 1 into a 16-bit channel for the purpose of reaching into the bass range with $Ax.  This is also necessary if you want to play the high range without tuning errors.

 

Secondly, using only 3 voices (plus a noise channel if you use the AY, that TI chip, or the 2A03 which is in the NES) still leaves you both TIA channels free if you wanted to use sound effects.  Is it as good as a POKEY?  It depends ... but if your needs are just three well tuned square waves, and good arcade sounds, this is a very well-priced alternative to scrounging after Ballblazer carts.  Plus ... I do believe they are still being produced today, unless I am mistaken?

  • Like 2

Share this post


Link to post
Share on other sites

The VTech Creativision is 6502 based and uses the SN76489 as well. As for being compatible with different CPUs, from a programming perspective that generally is not an issue. Only when it comes to interfacing it technically and electroncially there could be different ways to do it on a Z80, 6502, 680X, 68000, X86 etc.

 

The AY chip has a bit more bells and whistles than the SN76489, plus that it tends to easier generate low sound frequencies depending on the clock frequency you feed to it. Actually that is why so many Colecovision people get the Super Game Module (SGM) because it has an onboard AY chip which allows more bassy sounds than the SN chip is capable of.

 

However it depends on the clock. I believe the Colecovision feeds its 3.5 MHz Z80 CPU/video clock to the SN chip which makes it go down to 110 Hz at lowest, while it seems the Creativision feeds its 2 MHz 6502 clock that generates other sound frequencies for the same parameter values, and lower notes. I don't know what would be feasible in terms of the 7800, if it would feed its 1.79 MHz CPU clock as well which would perhaps add a full octave of lower notes than the Colecovision can produce, at the loss of some of the absolute highest frequencies only dogs and bats can hear anyway.

Share this post


Link to post
Share on other sites

Also the mention of 3 square waves + 1 noise is not entirely true in either of the SN and AY cases. The white noise tends to play at a few fixed frequencies and/or is linked together with square wave channel 3. This means if you want to make e.g. noise sweeps you lose a channel of sound unless you want the square wave to go along. I have (tried to) made music for both chips so I know the hassle. On the other hand the SN chip can combine one square wave and the white noise into a LFSR to create a very narrow, bassy sound that sounds super cool but needs its own frequency table. I know POKEY has some awesome sounds as well but this LFSR bass is something extra. The AY chip doesn't quite have it AFAIK but has some hardware envelopes and other features worth looking into if one goes that route.

 

Or well, how much is a FM/OPL synthesis chip these days? Can you replicate one with something like an Arduino, Pi Zero etc? I mean if you are developing new hardware you might as well want to look into all possible options. Take a leap out of the early 80's PSG range and into sounds of the late 80's, early 90's.

Share this post


Link to post
Share on other sites

If using a microcontroller like we did for Rikki & Vikki's BupChip isn't an option because it's "too new" you'll likely have to deal with NOS parts. I briefly discussed our reasons for going with a softsynth here, but at $4 - $5 per chip and the ability to purchase from a reputable vendor it felt like a no brainer.

 

1 hour ago, carlsson said:

Or well, how much is a FM/OPL synthesis chip these days?

It depends upon the family (OPL, OPLL, OPN, OPM, etc.) going down this route for the 7800 I still recommend the YM2413 - which is fairly capable, affordable, and doesn't take up too much board real-estate. The only issue is dealing with counterfeits.

 

Keep in mind with any of these options that some support circuitry may be required. Not all of them can get a good frequency range with the PHI2 clock available on the cartridge slot, and some might not be able to use it at all. The clock isn't stable either, if you're banging the TIA or RIOT it'll skew.

 

 

I still feel if you're going to spend the effort to replace Pokey, write a new driver, bla bla - a new mapper and board should go along with it as well. The available options are still fairly limited and we don't have, say, an MMC3 equivalent.

  • Like 2

Share this post


Link to post
Share on other sites

Using an SN, AY, SID etc chip with the 7800 would be an anachronism anyway, even if it is a time period accurate anachronism. Now that I think about it, many of the others may have been reimplemented in microcontrollers just like you point to, if price is a bit more important than hardware accuracy.

Share this post


Link to post
Share on other sites

It's not an anachronism if it's time period accurate ;)

 

There was actually a Famicom cart that had an onboard AY.  Think it was called Gimmick.

Share this post


Link to post
Share on other sites
4 hours ago, carlsson said:

Using an SN, AY, SID etc chip with the 7800 would be an anachronism anyway, even if it is a time period accurate anachronism. 

 

Anachronism in terms of what was historically used with the 7800, but not in terms of what might have been used on the system.  When Atari was looking for an off-the-shelf soundchip for the ST series of computers, it used the yamaha AY-3-8910 variant. One could imagine an alternate history in which Atari might place an AY-3-8910 in 7800 carts, instead of pokey or gumby, and it doesn't seem too far fetched to me. Anyway, homebrew itself is anachronistic in the sense you're using.

 

But, if we're going to do a cart redesign, truthfully I'd prefer a very basic, cheap, and ubiquitous microcontroller-based soundchip. While complicating emulation, this would allow for game-specific changes to the sound engine. So long as the specific micro family doesn't entirely go away, code porting within a family isn't usually a big deal, so this solution could stand for quite a while.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Sign in to follow this  

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...