Search found 3079 matches

by Stef
Wed Mar 24, 2021 8:58 am
Forum: Super 32X
Topic: Questions on emulating the 32X
Replies: 14
Views: 1625

Re: Questions on emulating the 32X

You can also try to read others 32X emulators sources to sort some of your issues. To be honest in Gens i do not emulate a lot of stuff about the SH2 CPU, i only emulated parts required to make all 32X games (as far i remember) working.
by Stef
Mon Mar 22, 2021 12:01 pm
Forum: Mega/SegaCD
Topic: Questions on writing a new Mega CD emulator
Replies: 117
Views: 52733

Re: Questions on writing a new Mega CD emulator

It was Steve Snake Nah, I believe he's talking about Mr. Quinn, of AGES. I forget his first name :-( He got all this stuff working well before any of us. he probably has some "internal" information I had no more info than anybody else did at the time. I had to go out and buy a SegaCD and burn about...
by Stef
Mon Mar 22, 2021 11:33 am
Forum: Video Display Processor
Topic: VDP Status Register
Replies: 23
Views: 11036

Re: VDP Status Register

Not too much surprised.. the game is really badly coded :?
by Stef
Mon Mar 08, 2021 10:16 am
Forum: Video Display Processor
Topic: VDP Status Register
Replies: 23
Views: 11036

Re: VDP Status Register

I never tested it on real hardware but it's likely to have some slowdown issues as well indeed..
by Stef
Sat Mar 06, 2021 10:40 pm
Forum: Video Display Processor
Topic: VDP Status Register
Replies: 23
Views: 11036

Re: VDP Status Register

This game suffers from slowdown in Gens too.. Afaik i wonder if developers got documentations about the MD hardware as the game does lot of mistake. One of it is that it's wrongly testing Z80 BUS REQ bit, i has to add a small delay between BUS request and actually BUS req ack status to avoid the gam...
by Stef
Sat Mar 06, 2021 10:26 pm
Forum: Video Display Processor
Topic: VDP 128Kb Extended VRAM mode
Replies: 44
Views: 41449

Re: VDP 128Kb Extended VRAM mode

None of these emulators (even Exodus as far i know) actually emulates that 128K mode so don't be surprised to not see behavior of the 128K mode here. BlastEm is the only emulator to (partially ?) emulate it so be sure to use this emulator which is the most accurate by far when you are testing obscur...
by Stef
Thu Mar 04, 2021 9:08 am
Forum: Mega/SegaCD
Topic: Popful Mail
Replies: 14
Views: 8680

Re: Popful Mail

At least you don't require single cycle granularity for "perfect sync" stuff. In Gens using ~80 cycles (MD 68k) slices was enough to get all sync issues fixed less or more (at this time PC were much less powerful so doing instruction slice wasn't really possible) so don't overthink that aspect. From...
by Stef
Tue Feb 16, 2021 4:01 pm
Forum: SGDK
Topic: Some questions about SGDK
Replies: 14
Views: 2011

Re: Some questions about SGDK

When you release a sprite, SGDK will just mark it as released and so can give its VRAM / sprite space back to another sprite but it won't "erase" VRAM. It's normal you always see the data in VRAM (if you're using VRAM viewer from emulator). Also after SPR_release(..) you need to call SPR_update() to...
by Stef
Tue Feb 09, 2021 2:23 pm
Forum: SGDK
Topic: Some questions about SGDK
Replies: 14
Views: 2011

Re: Some questions about SGDK

Doing that will force to wait for a complete frame (wait for vblank and doing attached vblank process). It does not guarantee though that after the call you are not in vblank anymore, if the process are shorter than vblank period (and it's likely to happen) then you will be still in vblank after the...
by Stef
Mon Feb 08, 2021 11:26 pm
Forum: SGDK
Topic: Some questions about SGDK
Replies: 14
Views: 2011

Re: Some questions about SGDK

What about using (posx + 4) >> 3, so it will indeed round the tile position. Then what about just testing multiple tile position, for collision you may need kind of bounding box collision type so it actually touch several tiles at once. (posx + 8) >> 3 for maxX and (posx - 8) >> 3 for minX , it's ju...
by Stef
Sat Feb 06, 2021 11:39 pm
Forum: Super 32X
Topic: DMA DEI
Replies: 4
Views: 1338

Re: DMA DEI

Indeed, Gens only implemented what was used by 32X :oops: and honestly not much was used so the Gens SH-2 core is pretty incomplete on IO side !
by Stef
Fri Feb 05, 2021 1:20 pm
Forum: SGDK
Topic: Get Tile Index of background specific position (X, Y)
Replies: 6
Views: 2490

Re: Get Tile Index of background specific position (X, Y)

Indeed, but you need to use the MAP resource for that :)
It's also why i said "usually you should have it in RAM or ROM as you initially set it yourself", normally you almost never need to directly read the VRAM to retrieve tilemap data value.
by Stef
Fri Feb 05, 2021 1:18 pm
Forum: Megadrive/Genesis
Topic: VDP Interrupt Processing
Replies: 3
Views: 1088

Re: VDP Interrupt Processing

Yeah, that is how it works :)
by Stef
Thu Feb 04, 2021 10:15 am
Forum: Megadrive/Genesis
Topic: VDP Interrupt Processing
Replies: 3
Views: 1088

Re: VDP Interrupt Processing

As long as M68K CPU acknowledge them.. if it doesn't then they remain pending indefinitely.
I don't think we can cancel them from VDP side.
by Stef
Thu Feb 04, 2021 10:14 am
Forum: SGDK
Topic: Get Tile Index of background specific position (X, Y)
Replies: 6
Views: 2490

Re: Get Tile Index of background specific position (X, Y)

Indeed there is no VDP_getTileMapXY(..) function ins SGDK. The reason of that is that it's somehow slow to retrieve tile index reading VRAM, usually you should have it in RAM or ROM as you initially set it yourself :) But i admit that in some situation it can be handy to directly get it from VRAM (a...