Search found 845 matches

by Sik
Wed Jun 19, 2019 11:46 am
Forum: Megadrive/Genesis
Topic: Random emudev bugs list
Replies: 1
Views: 67

Re: Random emudev bugs list

5) Lots of Titan Overdrive II issues: * there's no soft background hum when you first start the ROM like I hear on the recording of it (but I do hear the pong ball bouncing sounds) It's not trying to output any sounds besides the beeps at that point, any hum you hear is noise (´・ω・`) * the sound go...
by Sik
Mon Jun 17, 2019 5:14 pm
Forum: Mega/SegaCD
Topic: Documenting using the CD drive without the BIOS
Replies: 5
Views: 181

Re: Documenting using the CD drive without the BIOS

…so my guess was correct then. We need a new document (and by that I mean text, not source code) describing how to use the CDD. Even if just from a 68000 programmer viewpoint (rather than emulation viewpoint, which is a lot trickier and probably deserves its own separate documentation). So far the l...
by Sik
Mon Jun 17, 2019 5:09 pm
Forum: Sound
Topic: How DAC works ?
Replies: 8
Views: 145

Re: How DAC works ?

I recall from tests that the amount of amplification seems to differ between discrete and integrated YM2612 tho (which can ruin attempts at using it, though I suppose you could try detecting which version it is by checking the behavior of reading back the status…), i.e. the register bits are fundame...
by Sik
Sun Jun 16, 2019 3:11 am
Forum: Megadrive/Genesis
Topic: DETECTING RedKid2500-based consoles
Replies: 9
Views: 339

Re: DETECTING RedKid2500-based consoles

But even different revisions of real hardware have some different quirks, and again, there's also modded systems to account for (which more likely than not will work just as fine, yet could potentially trip some careless checks like trying to guess by measuring memory size). It's better to check for...
by Sik
Sat Jun 15, 2019 3:56 pm
Forum: Sound
Topic: How DAC works ?
Replies: 8
Views: 145

Re: How DAC works ?

$2C is a test register (hence why it's "undocumented") and from what I gather the exact behavior differs between the two YM2612 variants used on the Mega Drive. No proper game will use it to attempt to boost the DAC either (especially as it prevents the remaining channels from being used for FM). Th...
by Sik
Sat Jun 15, 2019 2:11 am
Forum: Mega/SegaCD
Topic: Documenting using the CD drive without the BIOS
Replies: 5
Views: 181

Re: Documenting using the CD drive without the BIOS

…OK no matter how much I try reading the CDD stuff I have no clue how the heck you'd play audio tracks (or how you'd tell when a track ends). And on top of that the docs I have seem to conflict with each other regarding some values (e.g. is status 0x00 no disc or stopped disc?). Any clues? From what...
by Sik
Sat Jun 15, 2019 2:07 am
Forum: Mega/SegaCD
Topic: Rewriting the BIOS
Replies: 1
Views: 73

Re: Rewriting the BIOS

Decompressing the existing BIOS in the firmware should be OK since it's the one the user already provided legally. Albeit this is what lawyers are for :​v (chances of Sega caring are probably zero anyway). Incidentally, it seems the BIOS is always located at a 32KB boundary, except in the case of th...
by Sik
Fri Jun 14, 2019 8:27 am
Forum: Megadrive/Genesis
Topic: DETECTING RedKid2500-based consoles
Replies: 9
Views: 339

Re: DETECTING RedKid2500-based consoles

You still may be better off not trying to detect emulators but rather the particular quirks, then you can catch multiple implementations sharing the same quirks. Redkid is kind of an exception since the registers in question are pretty much a feature unique to Redkid rather than a quirk. I suppose y...
by Sik
Thu Jun 13, 2019 7:26 am
Forum: Megadrive/Genesis
Topic: DETECTING RedKid2500-based consoles
Replies: 9
Views: 339

Re: DETECTING RedKid2500-based consoles

That could needlessly trip some modded consoles tho (and Tera Drive would trip the VRAM check as well). Magistr16 could also trip it since it has more work RAM (256KB) and you don't want to detect it since as far as we can tell its sound is fine. By general rule, you want to avoid needless collatera...
by Sik
Wed Jun 12, 2019 11:02 pm
Forum: Megadrive/Genesis
Topic: DETECTING RedKid2500-based consoles
Replies: 9
Views: 339

Re: DETECTING RedKid2500-based consoles

I should write an article about this at some point. You can fingerprint shitty clones by probing what happens when using invalid BCD values. This is the code I currently have albeit I need to verify it does what it's intended to do (at least it doesn't seem to crash). It's based on what Tanglewood d...
by Sik
Wed Jun 12, 2019 7:15 pm
Forum: Mega/SegaCD
Topic: Documenting using the CD drive without the BIOS
Replies: 5
Views: 181

Documenting using the CD drive without the BIOS

Since there has been discussion about the CDD last month I was wondering if we could start documenting how to use the CD drive without the BIOS (i.e. documenting how the BIOS does its stuff in the first place). Not sure whether it'd be easier or harder than decompressing the actual BIOS but it would...
by Sik
Wed Jun 05, 2019 3:35 pm
Forum: Megadrive/Genesis
Topic: 68K cycle timing test ROM?
Replies: 10
Views: 468

Re: 68K cycle timing test ROM?

…the 68000 user manual doesn't give vague "maximum value", look into that (section 8, if you wonder where the timings are). The only one where it's vague is with division (it just says it's around 140 cycles), and I think that's in large part because the underlying algorithm is complex enough that a...
by Sik
Tue Jun 04, 2019 2:31 pm
Forum: Mega/SegaCD
Topic: Bike shedding a new CD-ROM format
Replies: 20
Views: 651

Re: Bike shedding a new CD-ROM format

Yeah, CD+G pretty much kills the "no subcodes" idea. While the P and Q subcodes can be guessed (as they're used to aid with error correction and such) the rest can't, and they still make 75% of the byte, so you may as well store the whole thing. And while not on Mega CD, I recall hearing about at le...
by Sik
Fri May 31, 2019 11:55 pm
Forum: Mega/SegaCD
Topic: Bike shedding a new CD-ROM format
Replies: 20
Views: 651

Re: Bike shedding a new CD-ROM format

For what's worth it: I wouldn't be surprised if loading compressed data and decompressing it on the fly takes up less time than loading uncompressed data. Don't forget that reading from files is slow even with caching (especially if you're reading from hard disk, and some large Flash-based media can...
by Sik
Tue May 28, 2019 1:03 pm
Forum: Demos
Topic: Metal Blast 2277 - Sega Genesis / Mega Drive
Replies: 48
Views: 9271

Re: Metal Blast 2277 - Sega Genesis / Mega Drive

But they're German?

But yeah, as far as releasing games they… barely are heard of. They're more known as a supplier (especially the cartridge shells, those are pretty cheap).