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GB68k: Gameboy Emulator for 68k Calcs
Posted by Michael on 13 May 2005, 17:12 GMT

The idea has been floating around for years, but Ben Ingram is now the first person to implement a Nintendo Gameboy emulator that runs on the 89, 92+, and Voyage 200. GB68k is still under development, but so far features partial emulation of the Gameboy and its features, enough to get some games to work. I'm not very familiar with the innards of a Gameboy, but the readme lists specifically what is not yet emulated (things such as "Real time clock on MBC3" and "Sprite priority behind background layer"). This wonderful program reminds me of Tezxas, the ZX Spectrum emulator.

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Re: GB68k: Gameboy Emulator for 68k Calcs
Exbzurg Account Info

yay! now if i only had a 68k calc.

Reply to this comment    13 May 2005, 18:50 GMT


Re: Re: GB68k: Gameboy Emulator for 68k Calcs
gimpynerd  Account Info
(Web Page)

I suggest trying it out on VTI just to see it. It really is quite awesome.

Reply to this comment    13 May 2005, 18:59 GMT


Re: Re: Re: GB68k: Gameboy Emulator for 68k Calcs
slimey_limey  Account Info
(Web Page)

Emulator on emulator! (Then run that on Bochs, in BasiliskII.) Z80->68k->i386->68k->i386

Reply to this comment    20 May 2005, 18:25 GMT

Re: GB68k: Gameboy Emulator for 68k Calcs
Master_Zog  Account Info
(Web Page)

>first person to implement a Nintendo Gameboy emulator
Actually the second. TIGB was first, but wasn't publicised much. It's also very slow.

Reply to this comment    13 May 2005, 19:00 GMT

Re: GB68k: Gameboy Emulator for 68k Calcs
Travis Evans  Account Info

That's interesting. I would have thought that some Game Boy ROMs would be too large to fit in RAM or Flash ROM. I didn't even think something like this would be feasible.

If the Game Boy's CPU is being emulated, and the CPU is similar to a Z80, then would it also be possible to emulate ASM programs for Z80 calcs? Or would things like ROM call emulation make it difficult?

Reply to this comment    13 May 2005, 19:43 GMT

Re: Re: GB68k: Gameboy Emulator for 68k Calcs
gimpynerd  Account Info
(Web Page)

I think that the program to convert the roms also compresses them.

Reply to this comment    13 May 2005, 19:44 GMT


Re: Re: Re: GB68k: Gameboy Emulator for 68k Calcs
DWedit  Account Info
(Web Page)

Nope

Reply to this comment    13 May 2005, 22:16 GMT


Re: Re: Re: Re: GB68k: Gameboy Emulator for 68k Calcs
gimpynerd  Account Info
(Web Page)

Darn I read it wrong...it's the save files that are compressed...

I feel stupid...

Reply to this comment    13 May 2005, 22:28 GMT


Re: Re: GB68k: Gameboy Emulator for 68k Calcs
Jason Malinowski  Account Info

The gamebody's processor is a highly simplified Z80, but doing emulation of a 83+ would not only require a much more advanced emulator core, but you'd also have to emulate the entire 83+ OS as well.

Reply to this comment    13 May 2005, 21:31 GMT

Re: Re: Re: GB68k: Gameboy Emulator for 68k Calcs
benryves  Account Info
(Web Page)

Not really. It should be easy enough to interpret the ROM calls - most are left unused, thankfully. Rather than "emulate the TI-83 Plus", "emulate Ion with a few ROM calls" seems a much better idea.

Reply to this comment    13 May 2005, 21:43 GMT

Re: Re: Re: Re: GB68k: Gameboy Emulator for 68k Calcs
Jason Malinowski  Account Info

True. Perhaps I should dig into TIGCC

Reply to this comment    14 May 2005, 15:36 GMT


Re: Re: Re: Re: GB68k: Gameboy Emulator for 68k Calcs
burntfuse  Account Info
(Web Page)

There's a good 83 Ion emulator for the 86 called Ion86...

Reply to this comment    15 May 2005, 20:01 GMT


Re: Re: Re: Re: Re: GB68k: Gameboy Emulator for 68k Calcs
Travis Evans  Account Info

The 83 and 86 both use the same CPU, though. I figured emulating other CPUs would be harder, because all of the opcodes would have to be emulated.

Reply to this comment    16 May 2005, 18:28 GMT

Re: Re: Re: Re: Re: Re: GB68k: Gameboy Emulator for 68k Calcs
burntfuse  Account Info
(Web Page)

True...at least writing a Z80 emulator for the gameboy's processor would be a lot easier than writing an emulator for whatever processor the gameboy has that would run on a Z80.

Reply to this comment    16 May 2005, 21:06 GMT


Re: Re: Re: Re: Re: Re: GB68k: Gameboy Emulator for 68k Calcs
ExtendeD Account Info

<<I figured emulating other CPUs would be harder, because all of the opcodes would have to be emulated.>>
Well, this is what GB68k does.

And 68k-based calcs have also ROM Calls, which may be very similar to 83+'s ones. Mapping the ROM Calls to the native ones should not be so difficult (although I do not know anything of Z80-based calcs' OS).

Reply to this comment    18 May 2005, 09:02 GMT


Re: Re: Re: Re: Re: Re: Re: GB68k: Gameboy Emulator for 68k Calcs
slimey_limey  Account Info
(Web Page)

But the calling sematics for the ROM calls are probably different -- I know that the 68k series wants them to be pushed onto the stack in reverse order (right-to-left, following the C documentation) and the stack is word-aligned. I don't know whether the z80 requires word-aligned stack, seeing that it is an 8-bit processor.

Reply to this comment    20 May 2005, 18:28 GMT


Re: Re: Re: Re: Re: Re: Re: Re: GB68k: Gameboy Emulator for 68k Calcs
burntfuse  Account Info
(Web Page)

Well, yeah, and the API calls themselves are probably completely different too, but a "fake" gameboy API could be set up that would call the 83+'s API when needed.

Reply to this comment    21 May 2005, 18:52 GMT


Re: Re: Re: Re: Re: Re: Re: Re: Re: GB68k: Gameboy Emulator for 68k Calcs
burntfuse  Account Info
(Web Page)

Sorry, I got a few things backwards; replace "83+" with [target system] and "gameboy" with [system to be emulated].

Reply to this comment    21 May 2005, 18:54 GMT


Re: Re: Re: GB68k: Gameboy Emulator for 68k Calcs
Zeroko  Account Info
(Web Page)

The full Z80 core would not take up too much more code. I have written one before. Since it uses a jump table (I presume), it would not even be any slower, except maybe for the flags, but I have heard of some great success in that area by others. Anyway, I thought I heard the ZX Spectrum used a normal Z80. I made a PC-based TI-81 emulator, so if anyone is interested, I might try to port it to the TI-89/92+. All I would have to do is change the memory lookup code to support the TI-85 & TI-86.

Reply to this comment    14 May 2005, 14:51 GMT

Re: GB68k: Gameboy Emulator for 68k Calcs
DWedit  Account Info
(Web Page)

Will we ever see PocketNES-style scaling for this? PocketNES (on the GBA, emulating the NES, see URL) draws a flickering pattern of 6/8ths of all the scanlines, so it looks nice for a blurry LCD screen.

Reply to this comment    13 May 2005, 20:33 GMT

Re: GB68k: Gameboy Emulator for 68k Calcs
gimpynerd  Account Info
(Web Page)

Don't really know where to post this but I guess this is a good place.

I was playing Link's Awakening and I had the Tail Key and was going to the Tial Cave when it crashed...

The last thing I saw was some vertical lines. Also I think it was when I was at the edge of a screen.

Also I think there may be an issue with key recognizing. In Link's Awakening when you use your sword rapidly it doesn't finish a swing before going on to the next one. I didn't remember that when playing on a Gameboy. Also I think the piece of power and guardian acorn last forever but that is probably the clock issue.

I was really getting into the game too... I wish it didn't crash.

Hope I've been some help!

Reply to this comment    13 May 2005, 20:58 GMT

Re: Re: GB68k: Gameboy Emulator for 68k Calcs
Master_Zog  Account Info

Unfortunately I haven't had a chance to test most games in depth. There's probly problems with most games if you play for long enough. I've found at least one crash bug with the current version...I'll release an update as soon as I figure out how to fix it.

>Also I think there may be an issue with key recognizing. In Link's Awakening when you use your sword rapidly it doesn't finish a swing before going on to the next one. I didn't remember that when playing on a Gameboy
I'm guessing that you're just noticing it more on the emu because it's running so much slower. If there really is a problem somewhere, it's probly a cpu bug. I'll look at it.

>Also I think the piece of power and guardian acorn last forever but that is probably the clock issue.
Yeah, they probly use the timer for this. I need to figure out a way to put in the timer (without slowing things down). I may just hack it on (without worrying about the exact timings).

Reply to this comment    13 May 2005, 23:46 GMT


Re: Re: Re: GB68k: Gameboy Emulator for 68k Calcs
gimpynerd  Account Info
(Web Page)

I am willing to test games extensively for you. In fact I intended to fully complete Link's Awakening. My email is gimpynerd@gmail.com if you are interested.

Reply to this comment    14 May 2005, 00:34 GMT

Re: Re: GB68k: Gameboy Emulator for 68k Calcs
Robert McDermot  Account Info

I tried loading links awakening on my calc and I had to keep archiving as it transfered the 10 files. Then when I went to play it it said out of memory. Did I do something wrong?

Reply to this comment    15 May 2005, 21:12 GMT


Re: Re: Re: GB68k: Gameboy Emulator for 68k Calcs
Robert McDermot  Account Info

never mind. I got it to work after I reset my ram. I don't know where it pulled the extra memory from but it worked.

Reply to this comment    15 May 2005, 21:22 GMT


Re: Re: Re: Re: GB68k: Gameboy Emulator for 68k Calcs
katmaster200 Account Info

all stored RAM variables are cleared, like entries and Y variables

Reply to this comment    24 May 2005, 03:08 GMT


Re: Re: GB68k: Gameboy Emulator for 68k Calcs
Rakka Account Info

I think v0.3.1 has fixed this, as I've finished the first level, and in Gopongo Swamp with BowWow right now. No problems at all right now, excellent app :-)

Reply to this comment    25 May 2005, 22:18 GMT

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