Mega Drive on a Chip,NES on a chip?

[Dr_Frankenmiga]

Ok heres what I want to know I have many of these pirate systems lying about and I noticed when I took them apart to see how they worked the PCB is VERY,VERY small.Almost 1 chip in some.

After some searching I found that you can get well whats basically a system on a chip.However I cant seem to find a source of these anyone got any clues?

I want a few to see how I chould devolop a similar system.I have some ideas for a portable and a few plans drawn up.But I am missing that all important chip(s)

Edit : Its not really important what system the `system on a chip` is based on I need it for ideas and to see how things work etc.Atari,Sega,Nintendo,Commodore it dont matter.This is for development and testing.

 

[Kaneda]

Perhaps the JoyCom or Gunboy ?

or the 5in1 atari joy or namco joy ?

you even have 3rd party Genny pad for ex who put all the system on one black glued chip....

If you question is "how to make it ?", i don't have exemple, sorry

 

[Dr_Frankenmiga]

No probs I have some ideas on how to build.I wanted to know where and if I chould buy the chips,parts,components on there own instead of ripping apart other consoles.

 

[link343]

I do have a NES on a chip thing called Power Joy.

 

[Mask of Destiny]

An FPGA could do essentially what you want (or at the very least everything except the processor itself). It's basically a programmable IC. You can make all kinds of junk using them.

Of course, you'll probably get better a better power/performance ratio with an actuall chip, but doing a run of those tends to be rather expensive unless you're making a whole lot of them.

 

[Dr_Frankenmiga]

Whould that not require some serious coding skill?

Basically code the whole system in 1 chip like a sort of Emulator???

Might have to look into it though.Thank you for your help.

I have been in contact with companies and they sent me some free heatsinks and stuff cool eh?

Well we got ideas,we got designs,we stupmed for components and ways to actually get this to work.

Sorry if I seem stupid,but my coding skills are pretty poor.

 

[fonzievoltonov]

Coding this type of chip, to create a emulator (i don't know if i'm speaking about the same than MOD told) require a special coding langage called VHDL.

Very hard, sorry to inform.

And these chip(s) are very expensives.

http://www.vhdl-online.de/~vhdl/tutorial/

Btw, i saw a genesis with all the system in one glue chip on the net.

There was only the powerreceiver/videooutput at the rear of the console, a floppy connector to go at the glue chip (directly under the cartridge port), 2 floppy connectors to go 2 the 2 joypads and 4 cables to go to the ON-OFF/reset switch. Very impressive. I don't know why sega didn't used this technique to build a cheap portable console of a GBA size.

 

[Mask of Destiny]

Yeah, we're talking about the same thing. VHDL isn't the only programming option, but none of the methods are easy, at least not if you're used to normal programming. Logic design takes a different form of thinking.

The prices aren't too bad. You can get a 100,000 gate FPGA for about $20 US from DigiKey. If you're buying in bulk I'm sure you could find a distributor with better pricing. Of course, 100,000 gates may not be enough to implement enough of the hardware for it to be worthwhile. I'm not very experienced in logic design so it's hard for me to guess how complex of a device you would need for something like this.

 

[ExCyber]

I'm not very experienced in logic design either, but a "100K" device isn't going to be enough for a Genesis/MD. There's just too much hardware there - 136KB of RAM, 68K, Z80, YM2612, VDP, I/O ports...

NES on the other hand seems somewhat feasible (all gate counts are absurd guesses ):

6502 core: The original core is rumored to be around 10,000 gates. One free VHDL implementation has been synthesized and takes up about three quarters of a "20K" device.

pAPU main channels: Probably not much more than 1K gates; each channel basically has a clock divider and a counter

pAPU DMA: Not really sure how much this takes, but it's not very sophisticated. It's probably little more than an address counter and a state machine to read RAM (famous last words?)

Controller ports: 8-bit parallel-out shift registers. Two of them. Or one if you only want one port. Not much else to it, AFAIK.

PPU: can't be sure without synthesizing it, but it's not likely to be huge. The design is heavily optimized - there is no "real" palette hardware to speak of (colors are generated by phase-shifting square waves onto the video signal), and various registers and control signals seem to be multitasked in interesting ways. Has 256 bytes of sprite RAM, and 32 bytes (or so; I think the actual entries are only 6 bits) palette RAM.

RAM: 2K work RAM, 2K PPU RAM. Block RAM should take care of this in a reasonably-sized device I think.

 

[Mr Conan]

Instead of VHDL, you could always do it all in schematics if you're better with circuits than programing. Itll probably take a LOT longer to make, but you can usually get it to compile more efficiently than VHDL as long as your design isnt horrible. In a class i took i built a vga controller and the 2 guys i was working with made and tested a 20 instuction cpu in about 3 weeks. The 6502 has about 150 instructions, but I would think it could still be manageable as long as you kept it modular and have the spare time to want to build something that big in schematics. A nice logic analyzer cant hurt either. The only big problem really is if you finish the design and you cant get it to run fast enough... then youre pretty much screwd, whereas in vhdl its a lot easier to change things around.

As for that free 6502 cpu ExCyber mentioned, I took a look at it a while ago and I believe it still needs a few more instructions to emulate a nintendo's cpu since the nintendo uses a custom 6502. I dont think they would be all that hard to add if someone who knew vhdl decided to use that for their cpu.

Hmm now that I think of it mabe ill give an NES a shot sometime before my fpga skills go completely to waste....

 

[ExCyber]

Actually, AFAIK the NES 6502 does not have any instruction set enhancements apart from the typical undocumented 6502 instructions like LAX), just the integrated pAPU (PSG) and controller port decoder which are still controlled through memory-mapped registers just like any other peripheral. It also does not implement decimal mode, which should save on a few gates (though if memory serves, the stock Free-6502 distribution didn't have decimal mode either). Also, I was wrong about the controller ports eariler, the program actually reads them serially, not from a parallel-out shift register.

Anyway, if you really want to do it you should find the following documents (And this site in general) useful:

CPU/peripheral overview

pAPU/PSG reference

PPU reference

 

[antime]

A more radical approach would be to use a faster, simpler core and emulate the target. You could even design a custom ISA just for emulating that particular target, kind of like how Transmeta's ISA is designed for emulating x86 CPUs.

 

[timofonic]

Nah, here are people missinformed... Actually you can emulate completely all components of a Megadrive ( maybe not some as the PSU and conectors, lol ) using FPGA chips that arent to expensive, check those from Xilinx ( www.xilinx.com ). Here you has the Spartan line

Actually there are FPGAs that cost 90 EUR aprox. and has 1 million of logic gates!

 

[Dr_Frankenmiga]

Hmmm all good suggestions and information thanks.

But how do all these Pirates do it then `systems on a chip` all the suggestions so far whold be to far too expensive,time consuming,and require some serious electronics knowledge.I doubt any pirate whould bother and move on to something else.

Thanks for all the info so far.Been looking into I may still be able to pull this off.

 

[ExCyber]

But how do all these Pirates do it then

By contracting a chip fabrication plant to make them by the thousands, and then selling them to local integrators/distributors because "pirate" hardware is the mainstream in the countries where they operate.