Search found 161 matches

by supercat
Mon Aug 26, 2019 8:00 pm
Forum: General Stuff
Topic: Why preserve video games?
Replies: 27
Views: 14057

Re: Why preserve video games?

Subject: Why preserve video games? That's more of a systemic problem, I'm not saying that makes rights holders in the wrong automatically, but there is absolutely no system in place to make anything like this possible (at least that I'm aware of). Like if source code could be placed in escrow until...
by supercat
Thu Aug 15, 2019 8:47 am
Forum: Newbie Help Center
Topic: Do you/does it make sense to imitate function calls?
Replies: 18
Views: 8912

Re: Do you/does it make sense to imitate function calls?

It was kind of touched on by some people, but even cc65 doesn't strictly use the standard C calling convention by default where everything needs to be pushed onto the stack. Normally it uses fastcall. The last argument is placed in the A register (or AX for 16 bit values), and return value is also ...
by supercat
Sun Aug 11, 2019 11:42 am
Forum: General Stuff
Topic: What do you think of FPGAs?
Replies: 51
Views: 26585

Re: What do you think of FPGAs?

Wow, I never knew CMOS inherently took more transistors than NMOS. A CMOS gate that produces an inverted function of any combination of AND and OR gates with separate inputs will generally require two transistors (one each P-type and N-type) per input. An NMOS gate will require one N-type transisto...
by supercat
Sun Aug 11, 2019 11:22 am
Forum: General Stuff
Topic: Why preserve video games?
Replies: 27
Views: 14057

Re: Why preserve video games?

Arguing for preserving anything is always difficult. The decision depends on the value that future, not current, generations assign to it, which cannot be known today. Regarding whether video games are more or less worthy of preservation than other items: given the amount of time people spend on us...
by supercat
Sun Aug 11, 2019 11:19 am
Forum: General Stuff
Topic: What do you think of FPGAs?
Replies: 51
Views: 26585

Re: What do you think of FPGAs?

Good luck emulating a fully accurate Super Accelerator System with sub-pixel latency (ie: "none"), or even a few scanlines of latency, on any modern system. A Raspberry Pi isn't powerful enough, and a full-scale PC isn't real-time enough (I'm not sure it's powerful enough either). Just using a fram...
by supercat
Thu Aug 08, 2019 1:29 pm
Forum: General Stuff
Topic: What do you think of FPGAs?
Replies: 51
Views: 26585

Re: What do you think of FPGAs?

Well, there's another missing option here which is CPLD, which is kind of like a cheaper one-time-programmable FPGA. There are three general approaches that can be used to make any form of programmable logic devices programmable: 1. Use one-time-programmable fuses or antifuses which are selectively...
by supercat
Thu Aug 01, 2019 9:09 am
Forum: NES Hardware and Flash Equipment
Topic: OneBus mapper for standard NES?
Replies: 4
Views: 8349

Re: OneBus mapper for standard NES?

Yes, it's possible. Both the CPU and PPU are slow enough that one could multiplex everything. The problem is that it's I/O intensive, basically requiring a high pin count FPGA, and a large chunk of NOR flash, resulting in a price tag that'll make it hard to justify. And, of course, it can't be comp...
by supercat
Wed Jul 24, 2019 12:24 pm
Forum: Homebrew Projects
Topic: Fake John Wick nes game on real nes
Replies: 14
Views: 11273

Re: Fake John Wick nes game on real nes

It is impossible to write to palette RAM while rendering is enabled; the hardware inside the PPU that handles palette reads and writes cares about the output of the address bus multiplexer, and no part of the normal fetch cadence can ever place $3Fxx on the address bus. Ah, that would be a problem....
by supercat
Wed Jul 24, 2019 10:06 am
Forum: Homebrew Projects
Topic: Fake John Wick nes game on real nes
Replies: 14
Views: 11273

Re: Fake John Wick nes game on real nes

During horizontal blanking, the PPU is fetching sprite tiles. To prevent the PPU from hogging the VRAM bus, you have to disable both background and sprite rendering. In addition, your write sequence is 17 cycles from the last cycle of line 6 to the last cycle of line 10, and the window you have to ...
by supercat
Wed Jul 24, 2019 8:38 am
Forum: Homebrew Projects
Topic: Fake John Wick nes game on real nes
Replies: 14
Views: 11273

Re: Fake John Wick nes game on real nes

Like I always say, mid-screen palette changes are notoriously hard to pull off on the NES. You need at least one blank line when doing it, because one hblank simply doesn't give you enough time to 1) disable rendering; 2) set the palette address; 3) write the new color; 4) restore the scroll; 5) re...
by supercat
Thu Jul 18, 2019 3:25 pm
Forum: Newbie Help Center
Topic: Some hardware questions
Replies: 15
Views: 5770

Re: Some hardware questions

Implementing a ROM or RAM emulator in a CPU will seriously tax your CPU. The most famous example of success is the Atari 2600's Harmony Cart, which emulates a 32KB ROM (and a few special functions) used by a 1.2MHz 6502 with a 70MHz ARM. If one wasn't interested in using the 6502 for game logic bey...
by supercat
Tue Jul 02, 2019 1:44 pm
Forum: NES Hardware and Flash Equipment
Topic: FS306: Mixed CHR-ROM/CHR-RAM cartridge
Replies: 30
Views: 19237

Re: FS306: Mixed CHR-ROM/CHR-RAM cartridge

For whatever reason, although someone could still implement transparent latches using the feedback paths in "Simple" or "Complex" modes, people just generally didn't. Suppose one wants to design a latch that will hold its value if LatchEnable is low, or copy the state of D0, D1, D2, or D3 based upo...
by supercat
Sat Jun 29, 2019 1:25 pm
Forum: NES Hardware and Flash Equipment
Topic: 2A03 external bus signals on internal register accesses
Replies: 8
Views: 7457

Re: 2A03 external bus signals on internal register accesses

I have a question about the 2A03's bus signals: Do these always behave the same way for internal register accesses as they do for external accesses? The only thing that does not show up externally with the 2A03 is reads from $4015, which happens from a special 2A03-internal bus. For the 2C02, what ...
by supercat
Fri Jun 28, 2019 3:46 pm
Forum: NES Hardware and Flash Equipment
Topic: Putting second PPU inside cartridge
Replies: 13
Views: 9855

Re: Putting second PPU inside cartridge

It makes me think that since the very first clock, there is some counter inside PPU that clocks the frame timing and moment when it generates VBLANK is deterministic, not dependent on disabling and enabling rendering On the 2C03,4,5,7 that's correct; frame timing is a function of when the PPU is re...
by supercat
Thu Jun 27, 2019 10:14 pm
Forum: Newbie Help Center
Topic: 8x16 and whatever else unreg wants to know
Replies: 1557
Views: 403392

Re: 8x16 and whatever else unreg wants to know

Does this game/thing use panning/scrolling at all? If you're trying to do everything in single-screen and you aren't using panning/scrolling, my advice is: don't. Make use of the memory in the adjacent nametable and flip-flop between them using bits in $2000. You draw to the one that isn't visible,...