Ultimate 2532(or 2352) PROM MegaCart!!! ... kinda

While visiting my favorite local Electronics Surplus Store I came across this odd 24 pin fake IC to IC cable, which gave me a cool idea. One very common (and boring) tasks in my line of work is doing adapters to run ROMs (custom and whatnot) on the real hardware for analysis. This setup makes it pretty easy (and solderless) to try stuff around, especially difference in CPU<->BUS<->ROM handshaking signals like !CS !CE, !E whatever, and also configuration of adress lines.

Systems that typically use such 24pin ROMs include
VIC-20
ATARI 2600
MPT-03 - Arcadia 2001 clone(pictured)
Odyssey2

This particular breadbreadboard setup allows me to quickly "audition" up to 16 different 4KB Arcadia ROMs using DIP switches.

That big mysterious gate array

Analyse.. don't Destroy (a Casio PV-1000)

I'm not a console collector nut, I'm a audio chip collector nut. There are countless game consoles and computers out there that I dont care much about because they all contain the same chips. (AY-3-8910 is nice, but you can only have so many of them).

What I'm looking to acquire at this point are the most obscure ones which contain custom/unique sound generating chips. You've heard about the CASIO PV-1000 before?

Don't worry, only the most die hard console collectors did. And they would die for it too. There are very very few such consoles out there and I got mine a bit by chance, and it was an impulse buy.

At 300$ (ebay), you just can't afford to ruin it can you? (I'm not a movie producer). And I look forward to its resell value once im done with it. Thats where the challenge comes in... how do I take a device that comes with just a NTSC-J RF adapter and get good enough audio results with it? (the RF channels on North american and Japan dont match... dont try)

The closest I got to getting a picture/sound from the default unit as is was to use a ANALOG/DIGITAL USB TV tuner, which had by chance a NTSC-J mode:

Not that bad, but, the audio was horrendous, and really not usable for my tests. However I've hacked nearly all my consoles in order to have separate composite video/audio from RCA jacks, so on top of some test equipement, i've got a few hunches on how to solve this cleanly.

the RF box is tied to the main motherboard in a very clean way:

A few minutes with my multimeter, from top to bottom:
1)9VDC (current for the amplifiers in the RF sections i assume)
2)GND
3)Composite Video Out.. YAY!
4)GND (same as 2)
5)Audio Out...  w00t!

Connecting Aligator jumpers to truncated ends of a RCA and to the pins 3,4 and 5 did provide me with a temporary solution, but surely isnt very practical for a longer term analysis.

Oups, where did the RF box go? (in a safe place in case I resell it and the buyer really is after lots of  pain and suffering).

Much better.
 From the outside:

Enjoy the OK quality outputs:

Meet my new friend the logic analyser!

Its time to step my game up. So I've decided to acquire the immese value for money Saleae Logic Analyser. This baby will allow me to analyse and record a bunch of stuff that really cant be handled with a sound card and an oscilloscope alone. (namely serial digital audio prior to being sent to DACs)

As a test to see if everything works, and that i can get sufficient time resolution on this, ive done a simple setup which consists in a 4Mhz clock and a Hex inverter (74LS04). I done my recording test using 24Mhz on my MacBookPro's USB2 port. And im quite happy with the results. Not bad for 15 minutes of unboxing the thing!

These are not the chips you're looking for

[EDIT dec7th 2009] the wikipedia page has been corrected!Thanks!

According to wikipedia there is a VRC6 chip inside a North American Nigel Mansell "World Challenge" cartridge. Well no, there isn't. And there's no such thing as "World Challenge" either, only "World Championship" same difference.

Looks like Ill have to dig up the big bucks for a Japanese Castlevania 3 cart.

TED: The 100$ noise pattern

00000000110010000100010111111101010011100
11000111111000001011010101101111101111000
10000001001111001110110011111001011101011
00101011110100011000010100000111000110101
11000011110110110100001101110111001001000
11101001100110100100110110001010101000100
101001011  (low frequency version: audio)

Working C16's and plus/4 are HARD to come by,
and people need to pay the price for a working
MOS8501 CPU and a MOS8360 TED chip.

I needed a real machine to analyze the TED noise pattern
(and pitch ranges) for a future version of chipsound,
so I won a working plus/4 on ebay, which cost me 100$
(with shipping) to Montreal, not that bad actually.

The TED will be included in an update for completism more
than anything, because the only thing that's unique about it
is its noise pattern. Otherwise its a very simple VDC
unit that generates 2 voices. Many plus4 users actually hook
up SIDs to the machine, or just use the chip as a DAC,
which is the case for demos such as this one

Confirmed VICE plus4 emu generates the same pattern,
so all is good.

(100$/255bits = 39cent/bit)

But is it cute??

 

Hum, nah, im not cleaning that GUNK to find out!

Full AY emu prototype

Well I've talked about this before, but I'll say it again.
Designing a synthesizer that claims full chip authenticity and playability at the same time is the toughest challenge I'm faced with.

It hard to give access to powerful sound tweaking possibilities available on some chips when the synth paradigm you are basing your whole design on is of the standard
[voice0 + voice1 + voice2 + (...) + voiceN = mix]
variety

Look at this signal path for instance:

It becomes clear that something like this doesn't fit that particular mold.

The AY has five generators: 3 tones, 1 noise, and 1 envelope.
It also has three independent audio output pins, that are mixed in the analog world differently in all the AY-based systems.

Now each of the output has its own tone generator, but it can also be mixed with the lone noise pattern (either, or combined with a binary AND). On top of that each output can have its volume changed independently (16 log steps), or be amp-modulated by the LONE Envelope generator. (more in the spec)

Anyone who's messed with an AY knows that the fun comes from mixing the env/tone+noise in certain ways which can make unique drones/beats that any IDM/Experimental student would enjoy.

But you can't currently do these in chipsounds v1.0 due to voice paradigm its based on. From recent user questions on the AY matter, it surprised me how programming a straight chip emu sounds like a hard task.
But in reality, in comparison to trying to make it fit in ARIA/SFZ, making a separate module that purely emulates the chip in bit perfect manner (and with all its limitations) is really not the challenge it appears to be.

The AY is a relatively simple digital state machine

Here is a snapshot of my current prototype (made using Bidule's C++ SDK):



And the type of drones you can dynamically make by moving the sliders here:
Example A
Example B

Its currently unclear if/how this will be integrated in chipsounds, or given for free for Bidule users. Please stay tuned!