Search found 939 matches

by Sik
Sun Jan 17, 2021 6:59 am
Forum: SGDK
Topic: Getting the R, G, B components of a palette color
Replies: 6
Views: 499

Re: Getting the R, G, B components of a palette color

It's 0000BBB0GGG0RRR0 actually

blue = (color >> 9) & 7;
green = (color >> 5) & 7;
red = (color >> 1) & 7;
by Sik
Mon Jan 11, 2021 10:45 pm
Forum: Megadrive/Genesis
Topic: Discrepency in TMSS ROM Dumps?
Replies: 5
Views: 725

Re: Discrepency in TMSS ROM Dumps?

Pretty sure that all the Mega Drives with TMSS use the exact same ROM. Teradrive is its own unique thing which is why it has its own firmware, in fact unlike TMSS it does a lot more of stuff since it checks what kind of cartridge it is (as there are special Teradrive-specific cartridges) and reports...
by Sik
Thu Dec 31, 2020 6:13 am
Forum: SGDK
Topic: Namco arcade font
Replies: 3
Views: 503

Re: Namco arcade font

Nitpick: technically it originates from Atari (specifically Quiz Show, though it took a couple of games or so until most characters settled down, particularly 0, 3, 4 and W, and even then most games would still tweak some character).
by Sik
Thu Nov 19, 2020 10:06 am
Forum: Megadrive/Genesis
Topic: emulators or gamepad input problem?
Replies: 1
Views: 739

Re: emulators or gamepad input problem?

Something is definitely broken and it's not the emulators.

You'll need to figure out what's interrupting the inputs (faulty keyboard, maybe?)
by Sik
Fri Nov 13, 2020 11:23 pm
Forum: SGDK
Topic: Play wav music and sound effect
Replies: 19
Views: 5350

Re: Play wav music and sound effect

The problem with using up all 8MB comes from the fact that it breaks if a Mega CD is plugged in, whether it's being used or not (because the Mega CD will try to respond to its own range). This is true for stuff like Wondermega and CDX as well. There's a theory that manipulating /CART on the fly coul...
by Sik
Tue Sep 08, 2020 1:41 pm
Forum: Controls
Topic: XE-1AP
Replies: 4
Views: 8608

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: 5676

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: 5676

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: 972

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: 5676

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: 5676

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: 5676

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: 12797

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: 5676

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: 7622

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).