I understand that at this point the hdl is only for simulation but could someone at one point run a full gb on an fpga?
GateBoy will eventually do that for the whole reverse-engineered die.
Game Boy SM83 CPU Core
21–28 of 28 posts
Re: Game Boy SM83 CPU Core
#22Yay, the only bit of the die I couldn't transcribe for GateBoy! Looking forward to integrating this into the big simulator mess. Three frames per second here we come:D.
Raise the roof!
Re: Game Boy SM83 CPU Core
#23Earlier quoted context omitted.
Can they shut it down, though? Reverse engineering and emulation are all perectly legal despite Nintendo's claims to the contrary. The inner workings of their consoles are not protected.
They can threaten with legal action which is enough for some people to fold - regardless of whether it would succeed in court. Defending yourself in court is an expensive affair, unfortunately.
Some states have tried to make this better with anti-SLAPP laws. If the purpose of the litigation is to bankrupt the other party who is doing something legal, then the case can often be dismissed very early, and the plaintiff will have to pay a fine.
I am not sure if reverse engineering video game consoles fits into "a matter of public interest", but if you get nastygrams, it's probably worth talking to a lawyer. This might be something they can deal with in an afternoon and not a multi-year battle that bankrupts you.
https://en.wikipedia.org/wiki/Strategic_lawsuit_against_publ...
Re: Game Boy SM83 CPU Core
#24Earlier quoted context omitted.
Could you explain a bit how your project is different from the one in the article? Why did they implement the SM83 in HDL when you already have such an implementation? Also, I don't see any specific FPGA's mentioned, what sort of constraints do these projects have? Does it run on a 3$ one, or do you need something bigger /fancier? Edit: oh sorry didn't realize MIST is the device, it's an Altera Cyclone EP3C25
The one in the article is based directly on the die scans, while the MiSTer one is a completely custom implementation.
How is the custom implementation confirmed to be "cycle accurate"?
Re: Game Boy SM83 CPU Core
#25"Game Boy consoles use a custom Sharp CPU core that resembles Z80 and 8080 but is not exactly either." - well said but do know that the Z80 resembles the 8080 and it isn't exactly an 8080. To be fair the SM83 as coined here does have a few Z80 instructions but by and large it is an 8080 clone.
The Z80 fills some redundancies and gaps in the 8080 instruction set and adds the concept of prefixed instructions (via the CB, DD, FD and ED prefix bytes), but is otherwise compatible with the 8080 (it can run 8080 code which doesn't use any of the redundant opcodes which have been repurposed in the Z80). Looking at the Gameboy CPU instruction matrix ( https://www.pastraiser.com/cpu/gameboy/gameboy_opcodes.html ) ve…
Oh please, the big improvement in the Z80 over the 8080 was the IX and IY instructions plus the alternate register set 'AF etc and that's completely absent in the Gameboy CPU. The Z80 is not the father of the Gameboy CPU. A+B-B = A
The Z80 has some influence but it's pretty small.
Re: Game Boy SM83 CPU Core
#26Earlier quoted context omitted.
The Z80 fills some redundancies and gaps in the 8080 instruction set and adds the concept of prefixed instructions (via the CB, DD, FD and ED prefix bytes), but is otherwise compatible with the 8080 (it can run 8080 code which doesn't use any of the redundant opcodes which have been repurposed in the Z80). Looking at the Gameboy CPU instruction matrix ( https://www.pastraiser.com/cpu/gameboy/gameboy_opcodes.html ) ve…
Oh please, the big improvement in the Z80 over the 8080 was the IX and IY instructions plus the alternate register set 'AF etc and that's completely absent in the Gameboy CPU. The Z80 is not the father of the Gameboy CPU. A+B-B = A The Z80 has some influence but it's pretty small.
I wouldn't call the IX/IY instructions an improvement. They were so slow that they've rarely been used in performance-sensitive code (like games), it totally makes sense to drop them in a gaming device.
Same for the block instructions in the ED instruction range, quite convenient, but also very slow. LDI/LDD might have been useful for blitting bytes in unrolled loops, but since (AFAIK) the GB video hardware renders tiles and sprites directly, there's hardly a need for copying lots of bytes around.
The shadow register set wasn't all that useful either except for quickly saving state in interrupt handlers, but the additional registers take up a lot of die space.
On the other hand, the entire block of 256 bit twiddling instructions were obviously deemed important enough to keep them in the Gameboy CPU.
Re: Game Boy SM83 CPU Core
#27Earlier quoted context omitted.
Oh please, the big improvement in the Z80 over the 8080 was the IX and IY instructions plus the alternate register set 'AF etc and that's completely absent in the Gameboy CPU. The Z80 is not the father of the Gameboy CPU. A+B-B = A The Z80 has some influence but it's pretty small.
I wouldn't call the IX/IY instructions an improvement. They were so slow that they've rarely been used in performance-sensitive code (like games), it totally makes sense to drop them in a gaming device. Same for the block instructions in the ED instruction range, quite convenient, but also very slow. LDI/LDD might have been useful for blitting bytes in unrolled loops, but since (AFAIK) the GB video hardware renders t…
So you're basically saying you use a Z80 like an 8080. That's fine.:) But I will admit that the CB array of instructions are quite useful and Z80 in origin.
But just because you don't like a bunch of the Z80 die doesn't mean that the SM83 is a Z80 though. It's basically just an 8080 + CB and instructions that appear neither in 8080 or Z80
Still - I can see both from both sides now.
Re: Game Boy SM83 CPU Core
#28How do people learn how to reverse engineer ICs from pictures like this? I can make out the connections for the most part, but I wouldn't know where to begin to glean anything else.
Check out righto.com - you can start small and work your way up. You can learn to understand transistors from their shapes. There are also automated tools like what was used for Visual6502.org