Search found 45 matches

by ISSOtm
Fri Jan 18, 2019 6:17 am
Forum: GBDev
Topic: Font size: How big is big enough?
Replies: 4
Views: 7131

Re: Font size: How big is big enough?

I agree with Shonumi that contrast might have been a problem. This would stand especially true on a DMG, where even colors 0 and 3 can bleed into eachother, and perhaps the contrast wheel wasn't adjusted to their taste. On CGB/AGB, you can have true black contrast with true white (or #eee, perhaps?)...
by ISSOtm
Thu Jan 17, 2019 11:51 pm
Forum: GBDev
Topic: How do GPU/PPU timings work on the Gameboy?
Replies: 17
Views: 20601

Re: How do GPU/PPU timings work on the Gameboy?

And indeed, they do. I know nothing about no$gmb; BGB begins its disassembling from the address at the top of the screen, and assumes everything is code. Some known addresses are enforced as starting points, such as known entry points (vectors = rst + handlers), labels (if a SYM file is loaded) and ...
by ISSOtm
Thu Jan 17, 2019 9:49 am
Forum: GBDev
Topic: How do GPU/PPU timings work on the Gameboy?
Replies: 17
Views: 20601

Re: How do GPU/PPU timings work on the Gameboy?

That might make sense, as Blargg's ROMs write their output to serial
by ISSOtm
Thu Jan 17, 2019 1:05 am
Forum: GBDev
Topic: How do GPU/PPU timings work on the Gameboy?
Replies: 17
Views: 20601

Re: How do GPU/PPU timings work on the Gameboy?

Sorry, but I don't understand what you meant.
The only thing I grasped was that you're manipulating $FF01 and FF02, which are related to serial. Which is completely irrelevant to this topic. So..??
by ISSOtm
Mon Jan 14, 2019 11:39 pm
Forum: GBDev
Topic: How do GPU/PPU timings work on the Gameboy?
Replies: 17
Views: 20601

Re: How do GPU/PPU timings work on the Gameboy?

I wouldn't advise trying to emulate the boot ROM. It adds extra complexity, especially since the way the boot ROM is mapped to the address space varies depending on the model.

And there's also that the boot ROM is quite sloppily coded.
by ISSOtm
Mon Jan 14, 2019 5:45 pm
Forum: GBDev
Topic: Telling LYs? (test ROM)
Replies: 11
Views: 15733

Re: Telling LYs? (test ROM)

I think that last post was sarcasm.
by ISSOtm
Mon Jan 14, 2019 1:56 am
Forum: GBDev
Topic: How do GPU/PPU timings work on the Gameboy?
Replies: 17
Views: 20601

Re: How do GPU/PPU timings work on the Gameboy?

I'm going to say what tepples just said, just differently. The CPU and PPU run completely indepedently, the PPU pushes pixels and cycles its own modes no matter what the CPU does; the only direct influence the CPU has on the PPU is turning it on and off via LCDC bit 7. As for the PPU's modes, each o...
by ISSOtm
Sun Jan 13, 2019 6:45 pm
Forum: GBDev
Topic: Early stages of GB emu, trying to understand its interrupts
Replies: 2
Views: 6437

Re: Early stages of GB emu, trying to understand its interru

Instead of using games to test your emulator in the early stages, you should instead rely on test ROMs. The basic set is blargg's (note: the attached source code is incomplete/wrong due to the original source being lost, but it's better than nothing.) Try to pass these first - you won't go far if yo...
by ISSOtm
Sun Jan 13, 2019 10:59 am
Forum: GBDev
Topic: The first frame is always white (test ROM)
Replies: 7
Views: 12549

Re: The first frame is always white (test ROM)

Higan doesn't emulate this correctly, according to this game I'm developing. Soft-resetting it causes it to enter a boot-loop until the key combo is released, and this triggers the same behavior tepple's ROM tests (turn the LCD off after that first frame). Higan first shows a glitched frame (like, w...
by ISSOtm
Fri Jan 04, 2019 7:43 pm
Forum: Other Retro Dev
Topic: Game Boy LCD Rending Diagram
Replies: 13
Views: 20679

Re: Game Boy LCD Rending Diagram

That's basically what I'm trying to achieve with gb-asm-tutorial , though the presentation and purpose are different. And the project is frozen while i'm working on something else, too. (There's also a lot of information that's known by the community's members, but not written anywhere. Dunno if tha...
by ISSOtm
Fri Jan 04, 2019 7:00 pm
Forum: GBDev
Topic: Is a Game Boy faster than an NES?
Replies: 25
Views: 26348

Re: Is a Game Boy faster than an NES?

Here's a rather tame but interesting note to add in favor of the GB: The OAM DMA can be executed mid-frame. This causes the PPU to read $FF bytes from OAM for the duration of the transfer, causing up to 2 scanlines of blank sprites(*), but the BG is still shown. Prehistorik Man uses this to refresh ...
by ISSOtm
Fri Jan 04, 2019 6:37 pm
Forum: GBDev
Topic: The first frame is always white (test ROM)
Replies: 7
Views: 12549

Re: The first frame is always white (test ROM)

Quick note about this on SGB: the SGB appears to lose VSync when rapidly turning the LCD on and off, which causes the picture to scroll . Testing during development of my homebrew game also led to the conclusion that disabling the LCD on SGB simply causes the picture to stop updating, as evidenced b...
by ISSOtm
Fri Jan 04, 2019 6:31 pm
Forum: GBDev
Topic: halt in IME=0 && IF&IE==0
Replies: 1
Views: 8032

Re: halt in IME=0 && IF&IE==0

That's incorrect. The correct behavior of HALT is as follows: If IME == 1 : Execution is paused until IE & IF & $1F != 0 If IME == 0 : If IE & IF & $1F == 0 : Execution is paused until IE & IF & $1F != 0, after which execution resumes normally. This is basically the same as IME = 1, but the interrup...
by ISSOtm
Fri Jan 04, 2019 6:18 pm
Forum: GBDev
Topic: Halt check during halt
Replies: 1
Views: 6883

Re: Halt check during halt

I have asked Liji , developer of SameBoy (possibly the most accurate GB emulator as of now), about STAT interrupt timings. (Basically by how much I can expect the ISR to be delayed from HBlank due to for example multi-cycle instructions) He mentioned that on DMG exclusively , the interrupt might be ...
by ISSOtm
Fri Jan 04, 2019 6:10 pm
Forum: Other Retro Dev
Topic: Game Boy LCD Rending Diagram
Replies: 13
Views: 20679

Re: Game Boy LCD Rending Diagram

Actually, eevee made such a diagram. https://cdn.discordapp.com/attachments/303217943234215948/512632778873896960/game-boy-lcd-refresh-diagram.png (I know, I'm late.) As for the GBDev Wiki, it's rather sad that it's not up to the same quality as the corresponding NES wiki, partially as it's based on...