Search found 897 matches

by Sik
Thu Jun 13, 2019 7:26 am
Forum: Megadrive/Genesis
Topic: DETECTING RedKid2500-based consoles
Replies: 9
Views: 1172

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: 1172

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: 1308

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: 1678

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: 2760

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: 2760

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: 54
Views: 13765

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).
by Sik
Sat May 25, 2019 6:59 am
Forum: Mega/SegaCD
Topic: Questions on writing a new Mega CD emulator
Replies: 114
Views: 12851

Re: Questions on writing a new Mega CD emulator

I think the primary benefit of an open BIOS for the CD would be to help facilitate CD replacements. The CD drives on these systems are now so old that they're not very good, even when "new". The replacement I got for my CDX is barely any better than the old drive. An open BIOS would allow replacing...
by Sik
Fri May 24, 2019 3:56 am
Forum: Mega/SegaCD
Topic: Questions on writing a new Mega CD emulator
Replies: 114
Views: 12851

Re: Questions on writing a new Mega CD emulator

BIOS replacement could be cool. What I'd like to see most is a free (MIT/ISC/etc) BIOS, ala C-BIOS for the MSX, that can be dropped into any emulator out of the box, which can be swapped out for the real deal if desired. I'd definitely be willing to help with such a project. Yeah, that's why I want...
by Sik
Fri May 24, 2019 1:43 am
Forum: Mega/SegaCD
Topic: Questions on writing a new Mega CD emulator
Replies: 114
Views: 12851

Re: Questions on writing a new Mega CD emulator

Later we should probably write a new doc documenting the CDD well. By this I mean what each command does (including the format) and common sequences of commands (e.g. how to ask to read CD sectors or how to ask to play a given audio track). Not having to deal with the BIOS sounds like it should be a...
by Sik
Wed May 22, 2019 12:26 pm
Forum: Demos
Topic: MD-NICCC - a 3D Mega Drive experience by TiTAN
Replies: 56
Views: 8071

Re: MD-NICCC - a 3D Mega Drive experience by TiTAN

I believe it's just how they decided to handle the SH-2 side for the cartridge slot. My point was more that they did leave the strobe connected and hence they didn't remove the ability to write back to cartridge (even if only the Mega Drive side can do it). It's not like with /DTACK where not wiring...
by Sik
Wed May 22, 2019 12:43 am
Forum: Demos
Topic: MD-NICCC - a 3D Mega Drive experience by TiTAN
Replies: 56
Views: 8071

Re: MD-NICCC - a 3D Mega Drive experience by TiTAN

The write strobe is definitely passed to the cartridge slot, isn't it? I mean, otherwise games wouldn't be able to save. That's a completely different issue.

I wonder if not wiring /DTACK was an attempt to thwart Game Genie and the like (what addresses are used in those cases?).
by Sik
Tue May 21, 2019 5:46 pm
Forum: Demos
Topic: MD-NICCC - a 3D Mega Drive experience by TiTAN
Replies: 56
Views: 8071

Re: MD-NICCC - a 3D Mega Drive experience by TiTAN

Just looked up, SVP registers cover $A15000-$A15009 while 32X registers are all from $A15100 onwards. In other words, the exact addresses don't overlap.

That makes the whole part about leaving out SVP support particularly bad if /DTACK was indeed the only issue…
by Sik
Sun May 19, 2019 5:29 pm
Forum: Demos
Topic: MD-NICCC - a 3D Mega Drive experience by TiTAN
Replies: 56
Views: 8071

Re: MD-NICCC - a 3D Mega Drive experience by TiTAN

$A14xxx has the TMSS-related ports (on systems with TMSS, that is).
by Sik
Fri May 17, 2019 4:40 am
Forum: SGDK
Topic: Sega Genesis Dev Kit (SGDK)
Replies: 789
Views: 372677

Re: Sega Genesis Dev Kit (SGDK)

*insert shameless plug for SLZ* :​v I mean, SLZ has a tool written in C , only uses up as much RAM as the decompressed data (and the function call :​P) and the SLZ format is documented . And on the Mega Drive side it's literally just a single function call, so it should be easy to learn. Though I sh...