Search found 934 matches

by Sik
Tue Sep 08, 2020 1:41 pm
Forum: Controls
Topic: XE-1AP
Replies: 4
Views: 4611

Re: XE-1AP

I'll confirm the nibble swapping in PC vs MD mode when I get a chance. (´・ω・`) Anyway, there are reports that the throttle can end up backwards: https://www.sega-16.com/forum/showthread.php?35246-Xe-1-Ap-Controller-right-slider-is-reversed They tried rotating but no dice? Or are they misunderstandi...
by Sik
Tue Aug 25, 2020 4:33 am
Forum: Megadrive/Genesis
Topic: List of every detectable difference in Mega Drive revisions?
Replies: 17
Views: 1521

Re: List of every detectable difference in Mega Drive revisions?

I thought it was the other way, YM2612 always setting BUSY for a fixed number of cycles while YM3438 would set it only for as long as needed. But then again some people also say that the YM3438 is literally YM2612 on CMOS which should mean that the length of the BUSY flag should be identical… Which ...
by Sik
Fri Aug 21, 2020 3:26 pm
Forum: Megadrive/Genesis
Topic: List of every detectable difference in Mega Drive revisions?
Replies: 17
Views: 1521

Re: List of every detectable difference in Mega Drive revisions?

OK my notes so far (feel free to correct mistakes): ??? - TMSS (hardware version 0 vs 1) - YM2612 vs YM3438 MD1 VA3 onwards - Z80 open bus returns $FF instead of last value read MD1 VA5? and VA6 (only) - bits stuck when open bus with 68000? MD2 VA4 onwards - VSRAM is 64 words instead of 40 MD3 VA2 o...
by Sik
Wed Aug 19, 2020 7:11 am
Forum: Megadrive/Genesis
Topic: Weird timing issue?
Replies: 2
Views: 203

Re: Weird timing issue?

Address error (trying to do a word or longword access on an odd address). Old emulators didn't emulate it, but newer emulators (and the real thing) will throw an address error exception when that happens. The error seems to be at cmpi.w #-1, (A5) (with a5 = $10B27, which is odd), and a5 seems to hav...
by Sik
Wed Aug 19, 2020 6:48 am
Forum: Megadrive/Genesis
Topic: List of every detectable difference in Mega Drive revisions?
Replies: 17
Views: 1521

Re: List of every detectable difference in Mega Drive revisions?

I can confirm it's 0xFFFF because one of the reports was water flashing red in Miniplanets and red is the last color in its palette. The DMA bug where it loads garbage has been happening so often lately it's not funny, I guess it's starting to rear its head now because homebrew is way more widesprea...
by Sik
Mon Aug 17, 2020 9:15 am
Forum: Megadrive/Genesis
Topic: List of every detectable difference in Mega Drive revisions?
Replies: 17
Views: 1521

Re: List of every detectable difference in Mega Drive revisions?

Yeah the DMA transfer definitely still happens because the data in VRAM gets overwritten, it seems to act as if it was reading all ones (0xFFFF) as if the VDP couldn't access the 68000 bus. Maybe VDP is leaving the 68000 bus too early?
by Sik
Sun Aug 16, 2020 3:53 pm
Forum: Megadrive/Genesis
Topic: List of every detectable difference in Mega Drive revisions?
Replies: 17
Views: 1521

Re: List of every detectable difference in Mega Drive revisions?

The DMA thing sounds like the bus clash bug (where if both Z80 and DMA try to get to the 68000 bus at the same time the DMA transfer fails and loads garbage). All revisions suffer from it but some boards seem more susceptible than others at exposing issues (in particular early ones, but not necessar...
by Sik
Sat Aug 15, 2020 8:51 am
Forum: Sound
Topic: Sega CD Mode 1 support functions for SGDK
Replies: 25
Views: 8817

Re: Sega CD Mode 1 support functions for SGDK

It's writing the track number there before doing the BIOS call (see the move d1, (a0) immediately after that lea). Though… yeaaah not sure why those BIOS calls want a pointer to a single word when it could have been passed as-is through d1. Only explanation I can find is consistency since it seems t...
by Sik
Sat Aug 15, 2020 8:41 am
Forum: Megadrive/Genesis
Topic: List of every detectable difference in Mega Drive revisions?
Replies: 17
Views: 1521

List of every detectable difference in Mega Drive revisions?

I was thinking that about looking to make some test code that pokes different parts of the hardware to help narrow down which board revision it may be (in order to take an educated guess without having to have people open up the consoles), but uuuh while I remember some of the things that may change...
by Sik
Mon Jul 20, 2020 4:31 pm
Forum: Mega/SegaCD
Topic: mcd-verificator (CD core accuracy tests)
Replies: 24
Views: 3592

Re: mcd-verificator (CD core accuracy tests)

I do wonder if MCD+32X does work if you mod the 32X to pass through the /DTACK and audio lines. We know that just passing /DTACK is enough to make Virtua Racing work (which makes it baffling why they didn't do it, seeing how that solved all the SVP compatibility issues).
by Sik
Thu Jun 25, 2020 6:49 am
Forum: Megadrive/Genesis
Topic: Most compatible way to jump to game image on hardware - making my own cart
Replies: 21
Views: 2268

Re: Most compatible way to jump to game image on hardware - making my own cart

Yeah, "trigger" refers to the letter buttons (several manuals and in a handful of cases the games themselves refer to "A trigger" / "B trigger" / "C trigger"). Contrast with Start button and Directional Pad. B maps to the Atari button because the Master System controller has two buttons and their in...
by Sik
Wed Jun 24, 2020 12:42 pm
Forum: Megadrive/Genesis
Topic: Most compatible way to jump to game image on hardware - making my own cart
Replies: 21
Views: 2268

Re: Most compatible way to jump to game image on hardware - making my own cart

Edit - I'm putting together a new spreadsheet of Sonic mods changed by the IO fix, and I'm trying Griel's Quest again. It turns out that on the level select menu, for some bonkers reason buttons A and C are 'confirm' and B is 'back', which is outrageous! Uuuuuh, what else do you expect them to be? ...
by Sik
Mon Jun 22, 2020 9:46 am
Forum: Megadrive/Genesis
Topic: Most compatible way to jump to game image on hardware - making my own cart
Replies: 21
Views: 2268

Re: Most compatible way to jump to game image on hardware - making my own cart

If BlastEm barfs at a hack you can probably assume the issue is the hack :​P And yeah, games rely on telling apart between cold and warm boot not only because of the init skip stuff (not sure why Sega insisted on that ), but also because most games don't reset the options when you press the Reset bu...
by Sik
Fri Jun 19, 2020 5:30 pm
Forum: Megadrive/Genesis
Topic: Most compatible way to jump to game image on hardware - making my own cart
Replies: 21
Views: 2268

Re: Most compatible way to jump to game image on hardware - making my own cart

Yeah, interrupts have to be disabled because that's what 68000 does on reboot (remember not all systems have TMSS so on those the game is the bootstrap). And yeah, the state of the I/O ports on boot is how games tell apart soft reset from hard reset. Also, Z80 should be left reset on boot as well (a...
by Sik
Mon May 04, 2020 4:43 am
Forum: Megadrive/Genesis
Topic: Alternative to Vasm assembler?
Replies: 27
Views: 4314

Re: Alternative to Vasm assembler?

Make sure to enable errors. For some reason asmx has error reporting disabled by default… (why is that even a setting?!)