Search found 50 matches

by Trirosmos
Tue Nov 08, 2022 6:31 pm
Forum: NES Hardware and Flash Equipment
Topic: PowerPak MMC3 fixes: accurate IRQ, MC-ACC submapper, iNES 2 CHR-RAM
Replies: 51
Views: 4661

Re: PowerPak MMC3 jitter fix for loopy's mapper

With $2000=$10 every BG CHR fetch is A12 high, and NT/AT fetches are A12 low, but since NT/AT only takes 4 dots the M2 filter is not fulfilled and we continue as if A12 remains high while in a repeating NT AT CHR CHR pattern. At the end of a scanline we get an extra NT NT, then an idle dot that's e...
by Trirosmos
Tue Nov 08, 2022 2:49 pm
Forum: NES Hardware and Flash Equipment
Topic: PowerPak MMC3 fixes: accurate IRQ, MC-ACC submapper, iNES 2 CHR-RAM
Replies: 51
Views: 4661

Re: PowerPak MMC3 jitter fix for loopy's mapper

It seemed to always fail test #2, which is what we expected.

The weird part is that it seemed to only fail if it happened to land on the right CHR bank. Otherwise, it would always pass. He did try it several times.
by Trirosmos
Tue Nov 08, 2022 9:33 am
Forum: NES Hardware and Flash Equipment
Topic: PowerPak MMC3 fixes: accurate IRQ, MC-ACC submapper, iNES 2 CHR-RAM
Replies: 51
Views: 4661

Re: PowerPak MMC3 jitter fix for loopy's mapper

Hmm, seems like this test ROM doesn't properly initialize MMC3 CHR banks? It displays either a bunch of garbage or a solid white screen most of the time, if mapper state is randomized in Mesen. Anywho, Bucketmouse tried it on his MMC3A board and, on boots where the right CHR banks happened to be loa...
by Trirosmos
Fri Nov 04, 2022 7:55 pm
Forum: NES Hardware and Flash Equipment
Topic: PowerPak MMC3 fixes: accurate IRQ, MC-ACC submapper, iNES 2 CHR-RAM
Replies: 51
Views: 4661

Re: PowerPak MMC3 jitter fix for loopy's mapper

Otherwise they are open source, which Blargg suggested checking if the error message isn't enough: source Ah, neat! I'll take a look at these. It looks like the scanline tests sync to an even vblank with CPU cycle precision, then they run with the counter starting with values that should either hav...
by Trirosmos
Fri Nov 04, 2022 6:46 pm
Forum: NES Hardware and Flash Equipment
Topic: PowerPak MMC3 fixes: accurate IRQ, MC-ACC submapper, iNES 2 CHR-RAM
Replies: 51
Views: 4661

Re: PowerPak MMC3 jitter fix for loopy's mapper

So, what I'm seeing in attempt #9 is that in Wario's Woods, the bottom scanline of the green grass will turn black about ~48 pixels before the end of the line, but only on some resets. That's the behaviour we're looking for, right? I don't have a real Wario's Woods cart to compare. I believe that s...
by Trirosmos
Fri Nov 04, 2022 4:52 am
Forum: NES Hardware and Flash Equipment
Topic: PowerPak MMC3 fixes: accurate IRQ, MC-ACC submapper, iNES 2 CHR-RAM
Replies: 51
Views: 4661

Re: PowerPak MMC3 jitter fix for loopy's mapper

The IRQ logic really is kinda weird... I'll have to look into this in more detail later, now I'm really curious why that thing I wrote didn't work xD Oh, duh! I had misunderstood the counter's /reload signal as being asynchronous, but that wouldn't make much sense as it transitioning to 0 would imm...
by Trirosmos
Fri Nov 04, 2022 4:05 am
Forum: NES Hardware and Flash Equipment
Topic: PowerPak MMC3 fixes: accurate IRQ, MC-ACC submapper, iNES 2 CHR-RAM
Replies: 51
Views: 4661

Re: PowerPak MMC3 jitter fix for loopy's mapper

If MAP04.MAP wasn't rebuilt maybe it should be removed from that zip, just so nobody's confused about the contents if they download it. Done! Anyway, I did try building it but the IRQ never seems to fire at all. :S Not sure what the problem was. Ah, that's unfortunate :/ Wish I had a PowerPak so I ...
by Trirosmos
Thu Nov 03, 2022 6:35 pm
Forum: NES Hardware and Flash Equipment
Topic: PowerPak MMC3 fixes: accurate IRQ, MC-ACC submapper, iNES 2 CHR-RAM
Replies: 51
Views: 4661

Re: PowerPak MMC3 jitter fix for loopy's mapper

Alright, upon studying the schematic further, I realized my filter logic wasn't quite right, lol. It generated positive edges at the same points as the real deal, I think , but turns out a lot of the IRQ logic is triggered by the negative edges of the filtered A12 instead. This is almost verbatim wh...
by Trirosmos
Thu Nov 03, 2022 4:37 pm
Forum: NES Hardware and Flash Equipment
Topic: PowerPak MMC3 fixes: accurate IRQ, MC-ACC submapper, iNES 2 CHR-RAM
Replies: 51
Views: 4661

Re: PowerPak MMC3 jitter fix for loopy's mapper

So, it isn't quite the filter you suggested in your first post on this thread. I did try it like that, but never found a successful result with it. The implementation I had suggested at first is a fairly literal interpretation of the RE'd MMC3C schematic that Furrtek did by tracing decapped images ...
by Trirosmos
Wed Nov 02, 2022 4:36 am
Forum: NES Hardware and Flash Equipment
Topic: PowerPak MMC3 fixes: accurate IRQ, MC-ACC submapper, iNES 2 CHR-RAM
Replies: 51
Views: 4661

Re: PowerPak MMC3 jitter fix for loopy's mapper

To be clear, if I had to choose between a hardware-accurate mapper and a robust mapper, I would take the latter. I'm trying to make something that runs existing games well and without problems. There is of course a place for a separate, more accurate version as well, if these things are in oppositi...
by Trirosmos
Wed Nov 02, 2022 3:45 am
Forum: NES Hardware and Flash Equipment
Topic: PowerPak MMC3 fixes: accurate IRQ, MC-ACC submapper, iNES 2 CHR-RAM
Replies: 51
Views: 4661

Re: PowerPak MMC3 jitter fix for loopy's mapper

lidnariq wrote: Tue Nov 01, 2022 11:03 am
Trirosmos wrote: Tue Nov 01, 2022 10:25 am I believe an implementation closer to how the MMC3 handles it would be:
Rereading Furrtek's schematic, I think it's negedge
M2 is inverted on the PowerPak.
by Trirosmos
Tue Nov 01, 2022 10:25 am
Forum: NES Hardware and Flash Equipment
Topic: PowerPak MMC3 fixes: accurate IRQ, MC-ACC submapper, iNES 2 CHR-RAM
Replies: 51
Views: 4661

Re: PowerPak MMC3 jitter fix for loopy's mapper

That's kind of a weird filter. Seems to me like it'd filter out negative A12 edges, but any positive edge would still trigger the counter. I believe an implementation closer to how the MMC3 handles it would be: reg [2:0] a12_delay_line; wire a12 = a12_delay_line == 0 && chrain[12]; always @(...
by Trirosmos
Sun Dec 19, 2021 6:32 pm
Forum: NES Music
Topic: D[aw]PCM - A tool for editing and previewing DPCM samples in real time
Replies: 0
Views: 1195

D[aw]PCM - A tool for editing and previewing DPCM samples in real time

Hey, everyone! I've just published the first version of D[aw]PCM , a web tool that lets you import .wav files, process them and preview how they'll sound as DPCM in real time. This aims to improve the usual workflow of importing samples into Audacity, modifying them, exporting them, importing into F...
by Trirosmos
Thu Jun 10, 2021 11:54 am
Forum: General Stuff
Topic: Becoming an FPGA Engineer
Replies: 48
Views: 13335

Re: Becoming an FPGA Engineer

Instead of trying non synthetisable command like "delay", try searching if your FPGA have built in feature for programmable delay. For example - the cheap popular EPM240 has and it can be turned as follows: pd.png BTW. The signal initial value assignment is not synthetisable in al chips, ...
by Trirosmos
Tue Jun 08, 2021 7:25 pm
Forum: General Stuff
Topic: Becoming an FPGA Engineer
Replies: 48
Views: 13335

Re: Becoming an FPGA Engineer

Good to know that it doesn't make sense to do that. In what situation(s) could you correctly use a 'delay' or 'after' statement? Is that something for a different type of hardware? They're only useful for simulations. I believe some FPGAs have I/O blocks that allow for delaying a signal by a tiny b...