Search found 226 matches

by za909
Thu Feb 11, 2021 4:41 pm
Forum: NESdev
Topic: Question about DMC channel sample size
Replies: 6
Views: 2042

Re: Question about DMC channel sample size

Starting with $55 is the least noticeable way to do this compromise. A lot of games just assumed it was an even multiple of 16 and have a noticeable blip of noise at the end of all their samples. Even $55 has an audible and distinct tone to it, very much not silent, but definitely the least offendi...
by za909
Tue Jan 26, 2021 9:54 am
Forum: Newbie Help Center
Topic: Pausing during NMI execution.
Replies: 13
Views: 2701

Re: Pausing during NMI execution.

You are on the right track overall in thinking that it is a time-critical part of the program. During the Vertical Blanking period, the PPU is not accessing any of its memory, so this is the time when the CPU is free to change the nametables, palettes, refresh the sprite data by using the $4014 regi...
by za909
Sun Jan 24, 2021 8:24 am
Forum: NESdev
Topic: Question about DMC channel sample size
Replies: 6
Views: 2042

Re: Question about DMC channel sample size

I personally suggest ignoring the extra byte, or changing every sample to start with a byte of $55 or $AA to completely remove any unwanted change to the DAC level. It's not really worth doing all that padding to work around a barely noticeable artifact like that, but that's just my take on it.
by za909
Sat Jan 23, 2021 10:27 am
Forum: NESdev
Topic: Was there an NES expansion chip like SA-1
Replies: 85
Views: 14475

Re: Was there an NES expansion chip like SA-1

I would say to figure out what your software needs to do, and if it would benefit from extra hardware on the cart, and if there isn't already something that can provide you what you need. Like, the vast overarching majority of the stuff we churn out here as homebrewers is perfectly fine with the di...
by za909
Fri Jan 22, 2021 10:53 am
Forum: Newbie Help Center
Topic: Set a bit, clear a bit.
Replies: 10
Views: 2571

Re: Set a bit, clear a bit.

The original question has been answered, but as a tip, the following instructions are used for these operations: ORA - set bits of A that are '1' in the operand AND - clear bits of A that are '0' in the operand EOR - flip bits of A that are '1' in the operand For example if I had a variable that hol...
by za909
Fri Jan 22, 2021 10:42 am
Forum: NES Music
Topic: N163 Multi-Wave Sampling in FamiTracker
Replies: 28
Views: 3991

Re: N163 Multi-Wave Sampling in FamiTracker

This may sound close, but it is still not as good as writing your own code to use the N163 wave memory as a sample buffer. This is because Famitracker does not let you reset the phase accumulator of the N163 channels, which determines where the channel looks for the current waveform step in the memo...
by za909
Fri Jan 22, 2021 10:25 am
Forum: NESdev
Topic: Was there an NES expansion chip like SA-1
Replies: 85
Views: 14475

Re: Was there an NES expansion chip like SA-1

If we have two processors sharing the same RAM, wouldn't it require the co-processor to be clocked at the same rate as the NES CPU? Then the bus can alternate between the two cpu's every "half cycle" to make it appear as continuous (multiplexed) access? To me it sounds like it would make more sense ...
by za909
Sun Dec 27, 2020 12:31 pm
Forum: Test Forum
Topic: im 18 now uwu
Replies: 5
Views: 5077

Re: im 18 now uwu

And I thought I was one of the youngest members of this place at age 25 now.
by za909
Fri Dec 11, 2020 4:42 pm
Forum: NES Music
Topic: $4011 vs MMC5 $5011 for PCM streaming?
Replies: 17
Views: 4022

Re: $4011 vs MMC5 $5011 for PCM streaming?

If you want to make it 50% louder, you can send the same value to both (inverted on one). If you want to increase bit depth, if you could rely on MMC5 chips having a very consistent output volume (which you can't, but hypothetically if you could) I guess theoretically you could figure out a big tab...
by za909
Sun Nov 29, 2020 1:34 pm
Forum: NES Music
Topic: Preparing DMC samples
Replies: 5
Views: 2679

Re: Preparing DMC samples

I'm making a complete guess here and say that I would go with a low-pass filter before applying that noise. DPCM is naturally better at reproducing low-frequency components.
by za909
Thu Oct 29, 2020 2:10 pm
Forum: Newbie Help Center
Topic: rol vs asl, whats the difrence
Replies: 5
Views: 3301

Re: rol vs asl, whats the difrence

You can synthesize the non-existent "ASR" by using CMP #$80 before a ROR. This will copy the sign bit to the carry flag before you shift it in, so a negative number will stay negative.
by za909
Wed Oct 21, 2020 2:06 am
Forum: NESdev
Topic: What made UNROM such a popular mapper?
Replies: 11
Views: 4130

Re: What made UNROM such a popular mapper?

This actually makes me think, since you only need to watch for one bit of the address when accepting latch inputs, could the low bits of the address be used to easily set a register that's wider than 8 bits? with a setup like this, you'd write whatever to $8000 for bank 0, $8001 for bank 1, etc. I'...
by za909
Tue Oct 20, 2020 5:07 pm
Forum: NESdev
Topic: What made UNROM such a popular mapper?
Replies: 11
Views: 4130

Re: What made UNROM such a popular mapper?

I agree, it's straightforward to use, and it is very scalable. There only needs to be a single register by watching the ROMSEL and R/W pins so that the n-bit latch listens for writes to $8000-$FFFF. The unique part comes from an OR gate between the outputs of the latch and the high address pins of t...
by za909
Mon Oct 19, 2020 7:17 am
Forum: Newbie Help Center
Topic: NTSC or PAL?
Replies: 7
Views: 3369

Re: NTSC or PAL?

Asterix also comes to my mind as a PAL-specific game. This is because in the PAL region there's a much longer VBlank period, which allowed more VRAM updates per frame. Some games used this extended budget, and this makes them absolutely incompatible with NTSC consoles.
by za909
Mon Oct 05, 2020 8:29 am
Forum: Newbie Help Center
Topic: struggling with understanding pallets
Replies: 5
Views: 2148

Re: struggling with understanding pallets

For the background palettes, the first entry (at PPU addresses $3F00, $3F04, $3F08, $3F0C) in each palette actually refers to the so-called backdrop color, which is shared by the background palettes. This is not what's causing your weird colors, but it is something to remember in the future. This ma...