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How does a NOAC work?

Athosworld

Member
I want to know how does a NES On A Chip (NOAC) work, if possible, who invented it and why.

How does that chip read the data from the cartridge and executes it like the real NES.
Is it just some kind of extremely integrated 6502 or an FPGA?

My theory: When the chip gets power, it inmediatly starts reading the contents from the cartridge/NOR flash on boot and through a series of logic gates, it generates an AV output to the TV.
Im planning to do a decap of the blob chip.
Most of these NOAC systems have a COB in the controller that I suspect is just a shift register that sends signal to the NOAC because it isn’t powerful enough to execute a game and read directly from the controller.
You can see in this photo by hackaday.io, a system with a variety of blobs, are the functions of a NOAC spread over these chips?
6950B52D-5862-4CCC-8F7B-DD834B8E87E6.png
 

Pommie

Well-Known Member
Most Helpful Member
The NES had a completely separate computer to generate sound, a modified 6502 for the main program, 2k of RAM and the ROM in the cartridge. That has to be a full emulator or an actual NES using modern assembly techniques.

All you will achieve by decapping those blobs is to turn it (the NOAC) into a brick.

Mike.
P.S. I reverse engineered the NES back in 1987.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
The hackaday article makes it clear that the NOAC is purely the red board, the green one has the controller interfaces and output processing etc.

The main IC could be either some form of embedded 6502, or eg. something like an ARM based MCU emulating the 6502 and other functions for sound etc.

There are many of those available, as used in cheap mobile phones, that have RAM, sound and video etc. all in the one IC - and plenty powerful enough to emulate a 6502.

I can find eg. MSM8960 for less than $5 at one-off; that was pretty much the most powerful mobile phone system chip there was, about ten years ago.

There are likely far cheaper ones available for mass production.


The controllers are a hell of a lot more than "a shift register" as the nRF2401 is a two-way fully programmable RF link device.

It will have an MCU of some sort to manage it, set up the channel selection, handle controller link up etc.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
I want to know how does a NES On A Chip (NOAC) work, if possible, who invented it and why.

How does that chip read the data from the cartridge and executes it like the real NES.
Is it just some kind of extremely integrated 6502 or an FPGA?

My theory: When the chip gets power, it inmediatly starts reading the contents from the cartridge/NOR flash on boot and through a series of logic gates, it generates an AV output to the TV.
Im planning to do a decap of the blob chip.
Most of these NOAC systems have a COB in the controller that I suspect is just a shift register that sends signal to the NOAC because it isn’t powerful enough to execute a game and read directly from the controller.
You can see in this photo by hackaday.io, a system with a variety of blobs, are the functions of a NOAC spread over these chips?

Why are you obsessed with COB devices? - there's nothing you can do with them.

Presumably it's either got a hardware emulator in the COB's, or a software one - just as you can get software emulators on PC's. A 6502 is a fine processor, but it's VERY old, and VERY slow (by modern standards), easily emulated in software by a modern device.
 

Pommie

Well-Known Member
Most Helpful Member
The 6502 in the NES was not standard and had some instructions missing and some added - can't remember which.

There's a pretty good description of the NES hardware here.

Mike.
 

Athosworld

Member
The hackaday article makes it clear that the NOAC is purely the red board, the green one has the controller interfaces and output processing etc.

The main IC could be either some form of embedded 6502, or eg. something like an ARM based MCU emulating the 6502 and other functions for sound etc.

There are many of those available, as used in cheap mobile phones, that have RAM, sound and video etc. all in the one IC - and plenty powerful enough to emulate a 6502.

I can find eg. MSM8960 for less than $5 at one-off; that was pretty much the most powerful mobile phone system chip there was, about ten years ago.

There are likely far cheaper ones available for mass production.


The controllers are a hell of a lot more than "a shift register" as the nRF2401 is a two-way fully programmable RF link device.

It will have an MCU of some sort to manage it, set up the channel selection, handle controller link up etc.
These controllers are wired...
 

Athosworld

Member
Why are you obsessed with COB devices? - there's nothing you can do with them.

Presumably it's either got a hardware emulator in the COB's, or a software one - just as you can get software emulators on PC's. A 6502 is a fine processor, but it's VERY old, and VERY slow (by modern standards), easily emulated in software by a modern device.
I found the datasheet of one of those, it is a SinoWealth sh6578 and those found on cheap portable NOACs do HAVE a 6502 as CPU and an integrated LCD driver. Here it is.
 

Pommie

Well-Known Member
Most Helpful Member
Here it is.
No it isn't. That is similar to an NES but don't expect it to run NES games. To talk to the computer that made the sound (no idea what CPU) it had 1 port (might have been 2), that has 11. You basically uploaded code to the Audio CPU at boot up and then sent it commands that the code interpreted.

Mike.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
These controllers are wired...
Huh??? Are you in some parallel universe?

Bold added:

BOLT-ON FEATURES​

While the red PCB contains all of the standard NOAC hardware, the second green PCB appears to be home to all of the “secret sauce” features of the Generation NEX. Namely, the integrated receiver for the 2.4 GHz controllers and the stereo audio connectors.

In the controller we get our first unobstructed view of the Nordic nRF2401 radio module.

Even if it will take wired controllers as an alternative, it does not change the fact that the green board has those facilities, so the controllers in the article are MCU-based.

Very early wired controller could be nothing but switches and have a multi-way plug to connect to a console.
 

Athosworld

Member
Why are you obsessed with COB devices? - there's nothing you can do with them.

Presumably it's either got a hardware emulator in the COB's, or a software one - just as you can get software emulators on PC's. A 6502 is a fine processor, but it's VERY old, and VERY slow (by modern standards), easily emulated in software by a modern device.
Im not obsessed, it’s just that COB systems seem extremely obscure and mysterious to me.
 

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