Search found 567 matches

by Jarhmander
Sun Jan 08, 2023 9:05 pm
Forum: GBDev
Topic: GameBoy Program Counter behaviour
Replies: 4
Views: 1555

Re: GameBoy Program Counter behaviour

Open bus is whatever appeared on the data bus last; thus it is the last value the CPU have read/written. Indeed, if the last CPU fetch is the low byte of an memory address, then yes, that would be the open bus value, but if the instruction at 7FFF is a two or three byte instruction, then its remaini...
by Jarhmander
Sun Jan 08, 2023 12:27 pm
Forum: phpBB Issues
Topic: Weird smiley in some thread title
Replies: 11
Views: 2276

Re: Weird smiley in some thread title

You made it disappear, didn't you? I can't see it anymore.
by Jarhmander
Wed Jan 04, 2023 2:03 pm
Forum: phpBB Issues
Topic: Weird smiley in some thread title
Replies: 11
Views: 2276

Weird smiley in some thread title

Does anyone know what can cause that stray smiley? Does anyone see it when looking at that thread? On Chrome (108.0.5359.128) using Android 10. Screenshot_20230104_155133_com.android.chrome.jpg I can see it too when using Firefox (108.1.0 (Build #2015920443), 49ccb63dd+) It seems that the smiley is ...
by Jarhmander
Fri Sep 30, 2022 7:59 pm
Forum: Web Issues
Topic: HTTPS is broken
Replies: 30
Views: 47063

Re: HTTPS is broken

Thank you for your quick response!
by Jarhmander
Tue Sep 20, 2022 7:09 pm
Forum: General Stuff
Topic: Why a lot of 8-bit (or alike) developers think we loved excessive difficulty?
Replies: 49
Views: 15424

Re: Why a lot of 8-bit (or alike) developers think we loved excessive difficulty?

Call me a n00b, but I could only beat Megaman (1) on the PowerPak with save states. I also completed the 1st "run" of Recca with save states, there is simply no way I can beat this game normally, especially with the last boss which is insanely hard.
by Jarhmander
Tue Sep 06, 2022 11:32 am
Forum: SNESdev
Topic: Was the SPC700's noise channel based on the 2a03's noise channel?
Replies: 25
Views: 3206

Re: Was the SPC700's noise channel based on the 2a03's noise channel?

And I interpreted it as "it sounds bland in that game", sounding like a NES game. This was said in contrast to Super Mario World which used the LFSR noise cleverly to make good looking sounds. I wasn't aware of that, that's really neat.
by Jarhmander
Sat Jul 16, 2022 10:12 am
Forum: Newbie Help Center
Topic: 8x16 and whatever else unreg wants to know
Replies: 1626
Views: 572501

Re: 8x16 and whatever else unreg wants to know

Not exactly sure of what you want, but it really looks like you want indirection. With indirect indexed addressing mode (like in lda (zp), y instruction), you can have a pointer in zero page and change it to point to a fruit. Your routines can then use the zero page pointer to do their work. Prior t...
by Jarhmander
Sat Jul 09, 2022 5:37 am
Forum: NESemdev
Topic: "Fake" FF opcode vs a real one
Replies: 5
Views: 1222

Re: Fake FF opcode vs a real one

Not only a ROM can be partially full, there can be data intermingled with instructions, usually after a flow control instruction (jsr, rts, jmp etc) so the data won't be executed by the CPU. It is common to embed lookup tables alongside routines. And of course, usually well separated of the code, th...
by Jarhmander
Tue May 17, 2022 8:25 pm
Forum: NES Music
Topic: FDS unable to utilize the DPCM channel?
Replies: 11
Views: 1931

Re: FDS unable to utilize the DPCM channel?

Couldn't it be that some of the BIOS routines are timing sensitive and would be thrown off by "unpredictable" DPCM DMA fetches?
by Jarhmander
Fri May 06, 2022 6:58 pm
Forum: NES Hardware and Flash Equipment
Topic: Damaged PPU on top loader
Replies: 51
Views: 4280

Re: Damaged PPU on top loader

That's simply hexadecimal. $0400 == 1024 == 2^10. Other notation for hexadecimal is 400h or 0x400 (C, Python and other contemporary programming languages use the latter). $400 is simply 1 followed by 10 zeros in binary; in other words, in the context of address bits, A10 would be 1 and all the other...
by Jarhmander
Mon Apr 25, 2022 3:37 am
Forum: NES Hardware and Flash Equipment
Topic: Damaged PPU on top loader
Replies: 51
Views: 4280

Re: Damaged PPU on top loader

That may sound stupid, but have you tried using a small ceramic capacitor (100nF) in parallel with your 4.7μF?
by Jarhmander
Sat Feb 26, 2022 3:20 pm
Forum: NESdev
Topic: Glitch-free controller reads with DMC?
Replies: 113
Views: 84636

Re: Glitch-free controller reads with DMC?

Ben Boldt wrote: Fri Feb 25, 2022 7:02 pm Unrelated, but Shanghai II was an arcade game:

https://www.youtube.com/watch?v=ieZ1GgQ00oM

Who knew that? I had no idea. This might even be where the Sunsoft bass samples came from.
That's just ... Regular FM basses?
by Jarhmander
Sat Feb 19, 2022 4:35 pm
Forum: NESdev
Topic: Glitch-free controller reads with DMC?
Replies: 113
Views: 84636

Re: Glitch-free controller reads with DMC?

Not that I know of, and I don't see why it would.
by Jarhmander
Sat Feb 19, 2022 11:19 am
Forum: NESdev
Topic: Glitch-free controller reads with DMC?
Replies: 113
Views: 84636

Re: Glitch-free controller reads with DMC?

Yeah but page crossing due to normal PC incrementation has no special effect, only for (taken) branches. And the effect is not just one more CPU cycle, it affects interrupt timing... Though now that I read it, the IRQ/NMI is delayed when not crossing pages on taken branches...
by Jarhmander
Sat Feb 19, 2022 8:58 am
Forum: NESdev
Topic: Glitch-free controller reads with DMC?
Replies: 113
Views: 84636

Re: Glitch-free controller reads with DMC?

IIRC, if the branch instruction is the last of its page, there's no forward page crossing, because then PC point to the new page after fetching the instruction?