Search found 83 matches

by Fiskbit
Thu Mar 26, 2020 4:37 am
Forum: NES Hardware and Flash Equipment
Topic: TV-NET MC-1200
Replies: 1
Views: 113

TV-NET MC-1200

I just picked up a TV-NET modem and figured I'd post some pictures of its PCB, since I don't think there are any online yet. This is the MC-1200 version; I have an MC-1200B coming later for comparison, and there's also an MC-1200A and a TV-NET Rank 2 MC-4800. The TV-NET carts have a footprint exactl...
by Fiskbit
Sat Mar 21, 2020 2:04 am
Forum: NESemdev
Topic: On reset Stack Pointer status
Replies: 2
Views: 292

Re: On reset Stack Pointer status

There's a wiki page on the CPU power-up state here . Regarding the stack, SP initializes to 0 on power-on. When the CPU follows the reset vector, it treats it like any interrupt and tries to push P and PC onto the stack, but special logic makes the CPU perform reads instead of writes for these stack...
by Fiskbit
Thu Mar 05, 2020 10:52 pm
Forum: NESemdev
Topic: PPU wait for ready in Donkey Kong
Replies: 26
Views: 4204

Re: PPU wait for ready in Donkey Kong

Unless I'm misunderstanding, that works out to about 11.4 ms, not 3.6 ms.
by Fiskbit
Sat Feb 15, 2020 4:55 am
Forum: NESemdev
Topic: Mesen - NES Emulator
Replies: 807
Views: 341025

Re: Mesen - NES Emulator

Some kind of checksum has to be calculated before running the game to look it up in the database for correct header information.
by Fiskbit
Sat Feb 01, 2020 10:50 am
Forum: NESdev
Topic: FMV on NES (dream I had)
Replies: 16
Views: 3078

Re: FMV on NES (dream I had)

Cartridges can simply stream unique slivers (8x1 pixel strips and associated attributes) to the PPU. Examples of this include Doom on NES and Tom7's NES reverse-emulation work.
by Fiskbit
Sat Jan 18, 2020 6:44 pm
Forum: NESdev
Topic: Curious about MMC5 5209/520A registers
Replies: 26
Views: 5530

Re: Curious about MMC5 5209/520A registers

The vertical split is not that useful though, because it's tile granularity, not pixel. Meaning you can't do proper sliding transitions with it (well, you could hack the pixel position with sprites, but PITA). Leaves only vertical shooter HUD pretty much as the use case. It's only tile granularity ...
by Fiskbit
Tue Dec 10, 2019 1:09 am
Forum: NESdev
Topic: DPCM generates extra $4016 read pulse
Replies: 43
Views: 29148

Re: DPCM generates extra $4016 read pulse

My understanding, based in part on Disch's findings , is that DMC DMA normally (that is, outside of OAM DMA) takes 3 or 4 cycles depending on whether it begins on a get (even) or a put (odd) cycle, respectively. It attempts to initiate on put cycles, and if successful, it halts the CPU for 4 cycles ...
by Fiskbit
Mon Dec 09, 2019 11:51 pm
Forum: NESdev
Topic: DPCM generates extra $4016 read pulse
Replies: 43
Views: 29148

Re: DPCM generates extra $4016 read pulse

I can't tell for sure if this is what he means, but it actually is the case that ROL timing matters for synced joypad reads. When DMA initiates on a write cycle, it gets delayed to the next non-write cycle, which is usually the very next cycle. This changes the length of the DMA by a cycle. If this ...
by Fiskbit
Tue Nov 05, 2019 4:36 pm
Forum: NESdev
Topic: FCEUX + Midframe Palette Swap
Replies: 22
Views: 5410

Re: FCEUX + Midframe Palette Swap

rainwarrior covered most of what I had to say, but to add to that: At least with the official 2.2.3 release, I don't think FCEUX is suitable for this task. I recently worked on fixing color artifacts from a mid-screen palette update in Steins;Gate and FCEUX didn't render them at all. Mesen does show...
by Fiskbit
Mon Jul 29, 2019 2:57 am
Forum: NESdev
Topic: Question about object management (indirection / performance)
Replies: 7
Views: 5613

Re: Question about object management (indirection / performa

Yes, you'd allocate arrays each with a size equal to the maximum number of active objects. Performance-wise, I'm not sure there's a big difference between the two. Both of these are doing indexed accesses, so your loads will be 4 cycles (or 5 if cross-page) and your stores will be 5 (or 4 if your ar...
by Fiskbit
Mon Jul 29, 2019 1:44 am
Forum: NESdev
Topic: Question about object management (indirection / performance)
Replies: 7
Views: 5613

Re: Question about object management (indirection / performa

The way I've typically seen this done is to use a separate array for each variable, which is indexed into with the object's index. So, here, you'd have: LDX current_object_index INC object_x,X INC object_y,X (FYI, in your code sample, you're doing CLC after the ADC's; maybe this is intentional, but ...
by Fiskbit
Sun Jun 16, 2019 11:22 pm
Forum: NESdev
Topic: Graphical glitches on the Everdrive
Replies: 44
Views: 27777

Re: Graphical glitches on the Everdrive

I got the opportunity to test this on some additional hardware a couple weeks ago. On my NTSC frontloader NES (NES-CPU-07, Rev G), both the NES and FC Everdrive N8s produced the same OAM corruption with oam_corruption_stress_test.nes, but the PowerPak did not produce any corruption. Notably, however...
by Fiskbit
Mon May 20, 2019 1:34 pm
Forum: NESdev
Topic: Why not read controllers in NMI?
Replies: 50
Views: 45855

Re: Why not read controllers in NMI?

According to previous findings and discussion , the OAM DMA-safe portion of PAL vblank is likely larger than NTSC vblank and the information on the wiki here is likely not accurate to the scanline. If your OAM DMA fits in NTSC vblank, it probably works on PAL. As far as emulator compatibility for sy...
by Fiskbit
Sun May 12, 2019 5:13 pm
Forum: NES Hardware and Flash Equipment
Topic: PPU BG rendering one dot early
Replies: 7
Views: 7098

Re: PPU BG rendering one dot early

Thanks for the reminders that there are restrictions on where on a scanline sprite 0 hits can occur; I had forgotten about this entirely. Still interested in what's going on here, but it sounds like it's not something that would have an effect on program execution. Also, the possibility of it being ...
by Fiskbit
Sun May 12, 2019 3:19 pm
Forum: NES Hardware and Flash Equipment
Topic: PPU BG rendering one dot early
Replies: 7
Views: 7098

PPU BG rendering one dot early

I noticed some really strange PPU behavior on a Japanese player's Twitch stream recently and am wondering if this is associated with a PPU revision or if it's some kind of hardware failure. Specifically, it looks like the PPU is starting and ending background rendering 1 dot early every scanline, re...