Search found 15 matches

by NickMass
Tue Jul 23, 2019 11:28 am
Forum: NESemdev
Topic: I need more info about the 6502 CPU instruction set.
Replies: 36
Views: 18632

Re: I need more info about the 6502 CPU instruction set.

I took a look at the obelisk site and it has stuff like this in it: A,Z,C,N = A+M+C What does it mean? For that example it means: Register A Flag Z (Zero) Flag C (Carry) Flag N (Negative) Get their updated values based on the result of adding these together: Register A M emory value of the instruct...
by NickMass
Tue Jan 10, 2012 12:41 am
Forum: NESemdev
Topic: Using TASes for emulator testing
Replies: 4
Views: 2648

I have been trying with limited success to get TAS's to sync with my emulator for a while now but have never had it work. I have been using HappyLee's Super Mario Bros. run for my testing and it desyncs before it even gets to the very first goomba. I have tried adding/ removing idle frames but it st...
by NickMass
Tue Dec 27, 2011 7:08 pm
Forum: NESemdev
Topic: Failing ALL blargg's tests but passing nestest.nes
Replies: 11
Views: 3589

A common issue people have that can break stack ops is with bits 5 and 4, I would look at http://wiki.nesdev.com/w/index.php/CPU_ ... g_behavior and make sure what you are doing matches the table in the B Flag section on that page.
by NickMass
Tue Dec 27, 2011 6:14 pm
Forum: NESemdev
Topic: Failing ALL blargg's tests but passing nestest.nes
Replies: 11
Views: 3589

Nintendulator always reports registers as having a value of FF so you cannot trust what it reports in the trace logs. Typically passing nestest.nes yet failing all of blarggs CPU tests means one your CPU flags isn't working correctly, I would check to make sure you are handling status bits 2, 3, 4, ...
by NickMass
Thu Sep 08, 2011 11:29 pm
Forum: NESemdev
Topic: SHX/SHY
Replies: 16
Views: 6314

This is what I had to do to get these opcodes passing Blarggs test. case OpInfo.IllInstrSHX: value = (RegX & ((addr >> 8) + 1)) & 0xFF; if((RegY + Read(opAddr + 1)) <= 0xFF) Write(addr, value); break; case OpInfo.IllInstrSHY: value = (RegY & ((addr >> 8) + 1)) & 0xFF; if((RegX + Read(opAddr + 1)) <=...
by NickMass
Mon Aug 08, 2011 7:40 pm
Forum: NESemdev
Topic: Sanity check on my CPU code (resolved)
Replies: 21
Views: 6971

It appears that FCEXU initializes 0x0000 - 0x0800 to a repeating value of 00, 00, 00, 00, FF, FF, FF, FF. This really shouldn't matter however as I can't think of any games that rely on uninitialized RAM values and Super Mario Bros. should certainly work with everything initialized to 00.
by NickMass
Sun Jul 31, 2011 3:33 am
Forum: Newbie Help Center
Topic: Mirroring or scrolling issue?
Replies: 7
Views: 3371

The Super Mario Bros. title screen needs accurate VRAM read/write buffer emulation and you have made a couple of small mistakes with it. In your ReadRegister2007() // Address in palette range -> No delayed read else Value = VRAM[Address]; needs to be changed to be something like // Address in palett...
by NickMass
Mon Jul 18, 2011 4:49 pm
Forum: GBDev
Topic: GB-Z80 test roms?
Replies: 2
Views: 4225

When I was working on my GB emu all I could find as far as test roms were the ones Blargg wrote here: http://blargg.parodius.com/gb-tests/ , cpu_instrs.zip is the most like nestest but is a bit more complicated and can't be run in the basic mode that nestest supports, however it doesn't require LCD ...
by NickMass
Thu Jun 16, 2011 11:15 pm
Forum: NESemdev
Topic: Scanline -1
Replies: 6
Views: 1989

Well it would be 340/3 cpu cycles instead of 341/3, so it would be 113.33
by NickMass
Tue Jun 14, 2011 7:24 pm
Forum: NESemdev
Topic: PPU memory mirroring
Replies: 2
Views: 3279

I believe $3000-$3EFF is simply a mirror of $2000-$2EFF.
by NickMass
Thu Jun 09, 2011 11:00 pm
Forum: NESemdev
Topic: How do you find bugs in your emulator?
Replies: 32
Views: 8371

Now I have some questions. First, what's with all the 4's? If you don't know what I'm talking about, run the Controller Test in one of the 3 emulators I mentioned. For the $4016 reads, you should get 4040404040404040. However, some other emulators (such as Nestreme) display all zeroes. The 0s are w...
by NickMass
Sat Jul 31, 2010 5:44 pm
Forum: NESemdev
Topic: A little help with Kevtris nestest.nes?
Replies: 27
Views: 7634

If anyone happens to have a better more accurate nestest.nes log that is as easy to read as the current one used for comparison I will gladly overwrite the current one. http://nickmass.com/images/nestest.log is just some log I found in a post on these forums made ages ago that I happened to use when...
by NickMass
Sun Jun 13, 2010 11:31 am
Forum: General Stuff
Topic: Emulator's first run - big time fail
Replies: 6
Views: 2460

By watching your screenshot I think you did the same as I did, made a static pallete of red, green and blue to see some output before caring about palettes, right? Yeah, that is exactly what I did, though there probably could of been some better colors to pick because it wasn't exactly easy to see ...
by NickMass
Sat Jun 12, 2010 10:44 pm
Forum: General Stuff
Topic: Emulator's first run - big time fail
Replies: 6
Views: 2460

When I finished the PPU on my emulator initially it was pretty useless and I happened to of kept a screen shot of how it looked running Balloon Fight for the first time http://nickmass.com/images/background.png Palettes and the background were completely broken but surprisingly the sprites worked ki...
by NickMass
Sun Apr 04, 2010 6:46 pm
Forum: NESemdev
Topic: New emu: SMB status bar flashes when scrolling
Replies: 9
Views: 6130

The emulator I've been working on has exactly the same issue with the blinking status bar, and it seems my tracer output is identical but a bit more verbose, here's what mine outputs if it can help diagnose what is going on. Correct: http://nickmass.com/emu/correct.txt Incorrect: http://nickmass.com...