Search found 215 matches

by za909
Wed Oct 21, 2020 2:06 am
Forum: NESdev
Topic: What made UNROM such a popular mapper?
Replies: 11
Views: 338

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: 338

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: 465

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: 298

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...
by za909
Tue Sep 15, 2020 1:41 pm
Forum: NESdev
Topic: Sprites will not show up
Replies: 12
Views: 1711

Re: Sprites will not show up

I'll try this method I guess. I'm just confused because the background colour shows up. What is the purpose of disabling background and sprites in the PPUMASK anyway? Is there any practical reason to turn this off? There are reasons to disable them. Normally, the PPU uses the same internal address ...
by za909
Mon Aug 17, 2020 2:18 pm
Forum: General Stuff
Topic: About 6502 common syntax standards
Replies: 11
Views: 1997

Re: About 6502 common syntax standards

If I may, I want to use this opportunity to complain about PCEAS non-standard syntax. I was bothered so much by its use of brackets for [indirect] addressing, that I started working on a PCE-specific fork of ASM6 just so that I could stick to what I'm used to. I should get back to that at some point.
by za909
Tue Aug 11, 2020 5:13 am
Forum: Newbie Help Center
Topic: Sprite 0 hit, do I understand correctly?
Replies: 6
Views: 1969

Re: Sprite 0 hit, do I understand correctly?

You can also use the sprite 0 flag to sync with the end of vblank. If the flag gets set during the frame it is only cleared when vblank is about to end. So once you are ready with everything that must be done during vblank you can start polling the flag again, this time waiting for it to be cleared,...
by za909
Sat Aug 08, 2020 9:00 am
Forum: Newbie Help Center
Topic: Sprite 0 hit, do I understand correctly?
Replies: 6
Views: 1969

Re: Sprite 0 hit, do I understand correctly?

Sprite 0 has no associated interrupt. The only thing you can do to run code at the exact time you want with it is if you "lock" the CPU in a loop that checks the flag continuously (called polling) and then exits when it sees that the bit has gone to 1. This means you can not do anything else until t...
by za909
Tue Jun 02, 2020 12:57 pm
Forum: Homebrew Projects
Topic: FROM BELOW [NES Homebrew] PRE-PRE ORDERS OPEN NOW
Replies: 77
Views: 22708

Re: What's Kraken (Tetris-like) [WIP NES Homebrew]

Hi, this sounds like an interesting little project. I'd be interested to try and put a small sound engine together (based on how much RAM, CPU time, ROM it should use, and other possible restrictions, how much space can I use for DPCM samples, etc.) if you think I'm "worthy" haha. You can check out ...
by za909
Sat May 16, 2020 10:39 am
Forum: NESdev
Topic: Mesen Debugger - Feedback/Feature Requests? (2018 edition)
Replies: 204
Views: 118199

Re: Mesen Debugger - Feedback/Feature Requests? (2018 edition)

Hi, I'd like to make a suggestion. During my DPCM-PCM endeavors I really could've used some of the still hidden stats of the APU, namely the 8-bit DPCM buffer state, which if I am not mistaken is implemented as a bit shifter, so there is no separate bits remaining counter. Seeing the state of this w...
by za909
Fri May 15, 2020 1:08 am
Forum: NES Graphics
Topic: Poll: How would you prefer a first-person shooter on the NES to look like?
Replies: 21
Views: 6625

Re: Poll: How would you prefer a first-person shooter on the NES to look like?

I wonder if lighting like this is possible on the NES. It really adds a lot to the mood of the level, like you are in a scary, enclosed space: https://m.youtube.com/watch?v=ieCqOjwh3fA
by za909
Thu May 14, 2020 1:09 am
Forum: NESdev
Topic: Linear interpolation overtones
Replies: 10
Views: 3081

Re: Linear interpolation overtones

I have spent a few days to implement this idea, and I got mixed results... Overall the sound is much noisier than before, though it seems to be better with low frequencies too. Sometimes those harmonics from before are still present, even though this time I can continously interpolate with the DPCM ...
by za909
Thu May 07, 2020 1:29 pm
Forum: NESdev
Topic: Linear interpolation overtones
Replies: 10
Views: 3081

Re: Linear interpolation overtones

I think lidnariq has the right answer. I agree. The samplebufferprev variable is a copy of the sample that was sent to $4011 about 90 cycles before, and had gone through an lsr long before that (in the previous IRQ). I have a very odd mixed method of buffering every odd sample, and sitting around h...
by za909
Thu May 07, 2020 2:23 am
Forum: NESdev
Topic: Linear interpolation overtones
Replies: 10
Views: 3081

Re: Linear interpolation overtones

Thank you for the answers. I am using unsigned 8-bit PCM, which is lsr-d once to discard the lowest bit that can't fit in the $4011 register. These are summed and divided by 2, I will post the relevant code later. (The next improvement is to add compatibility with the output of my external pre-proce...
by za909
Wed May 06, 2020 2:23 pm
Forum: NESdev
Topic: Linear interpolation overtones
Replies: 10
Views: 3081

Linear interpolation overtones

I have attempted to add linear interpolation samples to my now working PCM stream. I have run into some strange wave physics phenomenon I believe, but there is a possible explanation that stems from the code, I just don't know if it is a correct answer. So to demonstrate the horrible noise that I cr...