Search found 10707 matches

by lidnariq
Sun Jan 23, 2022 2:45 am
Forum: NES Music
Topic: Simulating 75% and 87.5% pulse wave in MIDI
Replies: 4
Views: 188

Re: Simulating 75% and 87.5% pulse wave in MIDI

Saw wave should have all harmonics, amplitudes of 1/n. Square waves are the only rectangular waves that have the same 1/n decay, but they only have odd components. So, Square at note N (1, 1/3, 1/5, &c) plus square at one octave up at half linear volume (1/2, 1/6, 1/10, &c) plus and square a...
by lidnariq
Sat Jan 22, 2022 6:15 pm
Forum: Reproduction
Topic: 512KB mapper 7 issue
Replies: 5
Views: 201

Re: 512KB mapper 7 issue

Just a guess: maybe they didn't extend the bus conflict prevention table from the original game, and so you can't switch out of the lower 8 banks predictably. (To find out, load the game in FCEUX or Mesen and check for writes to PRG where the value written isn't the same as the value at that address...
by lidnariq
Thu Jan 20, 2022 1:33 pm
Forum: NESdev
Topic: Initial state of PRGbanks with MMC1?
Replies: 8
Views: 255

Re: Initial state of PRGbanks with MMC1?

Nintendo's leaked MMC1 datasheet says that the banks are unknown on powerup. We've had people both report random power-up banks and reliable power-up banks. Several games include multiple reset vectors, not relying on any one memory layout being reliable enough. Lots of commercial games do not succe...
by lidnariq
Thu Jan 20, 2022 12:13 pm
Forum: Reproduction
Topic: Microcontroller for switching address pins LoROM and HiROM
Replies: 1
Views: 87

Re: Microcontroller for switching address pins LoROM and HiROM

No microcontroller, no. Ordinary 74xx series multiplexers can work, however.
by lidnariq
Wed Jan 19, 2022 12:38 pm
Forum: Newbie Help Center
Topic: Question about writing to internal PPU cgram mid frame (involving overriding the bus in the cartridge))
Replies: 1
Views: 89

Re: Question about writing to internal PPU cgram mid frame (involving overriding the bus in the cartridge))

The PPU internally synchronizes things on pixel edges (it uses two biphase clocks at 5.4MHz) so you can't "just" override M2 and call it a day. Unfortunately, the PPU treats CGRAM and "normal" PPU RAM writes almost the same way, so there's still a large delay of 6-9-ish pixels af...
by lidnariq
Sun Jan 16, 2022 11:20 am
Forum: NESdev
Topic: Early Hong Kong Micro Genius version with unusual encoder
Replies: 9
Views: 459

Re: Early Hong Kong Micro Genius version with unusual encoder

Definitely! The MK5060 appears to be what's responsible for pausing the PPU after the visible field is drawn... I guess it has to move the vertical sync too.
by lidnariq
Sat Jan 15, 2022 4:36 pm
Forum: General Stuff
Topic: nes-cpu-01 mainboard
Replies: 3
Views: 137

Re: nes-cpu-01 mainboard

Those green jumpers are stock, correcting for a design flaw.
by lidnariq
Sat Jan 15, 2022 11:47 am
Forum: General Stuff
Topic: nes-cpu-01 mainboard
Replies: 3
Views: 137

Re: nes-cpu-01 mainboard

Redherring recently managed to borrow and reverse-engineer the differences in the rev 1 and 2 NES mainboards. In his github: https://github.com/Redherring32/OpenTen ... -01_02.pdf

As far as scarcity: the first, and quite rare. As far as that being interesting? Not at all.
by lidnariq
Fri Jan 14, 2022 12:44 pm
Forum: Other Retro Dev
Topic: DOS VGA Tricks
Replies: 51
Views: 24225

Re: DOS VGA Tricks

According to VGA.TXT, you should be able to get fine X scrolls from 0 to 3 by writing 0/2/4/6 to 3c0h/13h, not 4...
by lidnariq
Thu Jan 13, 2022 5:01 pm
Forum: NESemdev
Topic: Count Errors Test ROM and some new DMC glitch info
Replies: 56
Views: 2673

Re: Count Errors Test ROM and some new DMC glitch info

Relatedly, here is the tiny test ROM that Fiskbit specified to record bus activity of: ;;; public domain (fiskbit+lidnariq 2022) ;;; assemble with cl65 -t none -o colliding-dma.bin colliding-dma.asm .setcpu "6502x" .CODE .org $E000 .include "constants.ca65.inc" reset: lda #$0F st...
by lidnariq
Thu Jan 13, 2022 4:55 pm
Forum: NESemdev
Topic: Count Errors Test ROM and some new DMC glitch info
Replies: 56
Views: 2673

Re: Count Errors Test ROM and some new DMC glitch info

On the NES, the controller ports are directly connected to the CPU - the signal is true for the entire time that the address bus is stable, and φ0/φ2/M2 aren't a factor. On the Famicom, the same signal is instead shaped by M2 - the joypads' CLOCK inputs are connected to the 40H368 that drives NOT(M2...
by lidnariq
Thu Jan 13, 2022 11:46 am
Forum: NES Hardware and Flash Equipment
Topic: Help to program 16 bit EPROMs on a 8 bit programmer
Replies: 5
Views: 343

Re: Help to program 16 bit EPROMs on a 8 bit programmer

Maybe the multiplexers I'm using, 74HC257 aren't bi-directional, are they? Correct. Does such multiplex exist? Yes, an analog multiplexer such as the 74'3257, 4053, or 4551. Should I add a 78L05 to the VPP pin to select the direction or there's some better way to do it? Normal voltage regulators wo...
by lidnariq
Wed Jan 12, 2022 1:24 pm
Forum: Other Retro Dev
Topic: DOS VGA Tricks
Replies: 51
Views: 24225

Re: DOS VGA Tricks

I wouldn't have expected 3d4/C and D to have worked - after all, there'd be less point in 3d4/18h if so. But it does sound like, based on what you're saying, that 3c0/13h is working... if not particularly interesting.
by lidnariq
Wed Jan 12, 2022 10:39 am
Forum: Other Retro Dev
Topic: DOS VGA Tricks
Replies: 51
Views: 24225

Re: DOS VGA Tricks

I have a real VGA to test, I might try later. EDIT: This is not going to work, documentation says it is used to calculate the start address at the top left of the screen, and it adds this to the start address register. start address registers are only updated once per frame :(. That feels weird to ...
by lidnariq
Tue Jan 11, 2022 10:32 pm
Forum: phpBB Issues
Topic: Animations (such as 'new post glow') eat up CPU/GPU resources
Replies: 4
Views: 264

Re: Animations (such as 'new post glow') eat up CPU/GPU resources

The only other ones I saw were in font-awesome.min.css (ugh)

has .fa-spin and .fa-pulse animations