Search found 94 matches

by byuu
Tue Jun 04, 2019 6:41 am
Forum: Mega/SegaCD
Topic: Bike shedding a new CD-ROM format
Replies: 20
Views: 8386

Re: Bike shedding a new CD-ROM format

It's true that subcode can be generated, but if you generate them, why even bother trying to read them? A fair question! It makes emulating the system easier. The Sega CD can read back the 96-byte subchannel data, it's what populates the current time information, the header/subheader registers, and...
by byuu
Tue Jun 04, 2019 3:06 am
Forum: Megadrive/Genesis
Topic: 68K cycle timing test ROM?
Replies: 10
Views: 5279

68K cycle timing test ROM?

Does there exist a test ROM that validates the cycle timings of 68K instructions? The timing documents out there are a bit tough to read, and even tougher to verify for every instruction given the way my core tries to move each cycle penalty to exactly where it's used (eg inside the bus read/write h...
by byuu
Mon Jun 03, 2019 4:21 pm
Forum: Mega/SegaCD
Topic: Bike shedding a new CD-ROM format
Replies: 20
Views: 8386

Re: Bike shedding a new CD-ROM format

The good news is that subcode follows a pre-defined ruleset for most discs. You can literally generate all of it, including the lead-in TOC and lead-out data, just through a BIN/CUE (with the exception of possibly not know how big the lead-in really is, but then it's supposedly standardized, even if...
by byuu
Mon Jun 03, 2019 2:56 am
Forum: Mega/SegaCD
Topic: Questions on writing a new Mega CD emulator
Replies: 114
Views: 34861

Re: Questions on writing a new Mega CD emulator

Sorry, I thought it might be helpful to mention things in case you wanted to work on it again. I understand, I'll stop giving you grief about it. Thank you again for your code. Buggy or not, it works, and that's the most important bit. It would have taken me ten times as long if I had to reverse eng...
by byuu
Sun Jun 02, 2019 1:44 pm
Forum: Mega/SegaCD
Topic: Bike shedding a new CD-ROM format
Replies: 20
Views: 8386

Re: Bike shedding a new CD-ROM format

That was what I meant, we could rip at BCD1 legitimately. Beyond that (C1/C2 and EFM), we currently cannot. And at this rate, we may never be able to.
by byuu
Sun Jun 02, 2019 7:41 am
Forum: Mega/SegaCD
Topic: Bike shedding a new CD-ROM format
Replies: 20
Views: 8386

Re: Bike shedding a new CD-ROM format

This would be great, but what exactly would you use to rip in these formats? There's different drives that can rip all of these components. I don't know if there's a single drive that can do all of them at once. The data is going to be in a consistent format 99% of the time anyway (I can easily rep...
by byuu
Sun Jun 02, 2019 6:32 am
Forum: Mega/SegaCD
Topic: Questions on writing a new Mega CD emulator
Replies: 114
Views: 34861

Re: Questions on writing a new Mega CD emulator

I added CDC DMA emulation, but Popful Mail still hangs after the Sega logo (the one after pressing start with the sound effect.) Both the main CPU and sub CPU are waiting on the other's messages, so a deadlock. Don't suppose anyone else ran into this issue with their emulators? Also, why does CDD co...
by byuu
Thu May 30, 2019 11:53 pm
Forum: Mega/SegaCD
Topic: Bike shedding a new CD-ROM format
Replies: 20
Views: 8386

Re: Bike shedding a new CD-ROM format

I can't find good documentation on what CHD actually does with CDs. All I see from the format is a really complicated way of describing and compressing blocks of data that has something like seven different header revisions. I'm really into simplicity in my formats, and try not to add anything that ...
by byuu
Thu May 30, 2019 7:46 pm
Forum: Mega/SegaCD
Topic: Bike shedding a new CD-ROM format
Replies: 20
Views: 8386

Bike shedding a new CD-ROM format

I managed to figure out the format of the lead-in TOC, save for a few bits (eg track A2's control bits.) I would like to create a new CD image format that captures everything: lead-in, track 1 pregap, lead-out, and all subchannel data. In doing so, we eliminate the need for CUE, SUB, and CCD files. ...
by byuu
Sat May 25, 2019 1:27 pm
Forum: Mega/SegaCD
Topic: Questions on writing a new Mega CD emulator
Replies: 114
Views: 34861

Re: Questions on writing a new Mega CD emulator

A reproduction BIOS doesn't need a full audio CD(+G) player interface. It doesn't even truly need a memory save interface (although that would help.) It just needs to run games. Emulators can make per-game backup RAM files. Or for Shining Force CD, backup RAM cart files per-game. All we really need ...
by byuu
Fri May 24, 2019 2:41 am
Forum: Mega/SegaCD
Topic: Questions on writing a new Mega CD emulator
Replies: 114
Views: 34861

Re: Questions on writing a new Mega CD emulator

I'm happy to try and help with some documentation in return for all the help, perhaps spare MaskOfDestiny some pain, hahah. I can capture CDC+CDD logs of booting a game. Luke Usher made a tiny 128KB "hello world" style demo for me which is pretty good for that. It feels really intimidating to see a ...
by byuu
Thu May 23, 2019 8:13 pm
Forum: Mega/SegaCD
Topic: Questions on writing a new Mega CD emulator
Replies: 114
Views: 34861

Re: Questions on writing a new Mega CD emulator

Still a crazy amount of things to implement (CD-DA most especially), but ... it works now ^-^;

Videos here: https://twitter.com/byuu_san/status/1131642295067897856

Thank you very much to everyone in this thread who graciously helped me make a 21-year long dream come true.

This one's to you, Atani.
by byuu
Thu May 23, 2019 3:05 pm
Forum: Mega/SegaCD
Topic: Questions on writing a new Mega CD emulator
Replies: 114
Views: 34861

Re: Questions on writing a new Mega CD emulator

!! oh wow, I never would have thought of that. I figured you'd just issue a seek and then a play.
I'll give this a try, hopefully that's what was missing, thank you!
by byuu
Wed May 22, 2019 6:19 pm
Forum: Mega/SegaCD
Topic: Questions on writing a new Mega CD emulator
Replies: 114
Views: 34861

Re: Questions on writing a new Mega CD emulator

Almost there ... the BIOS is reading the first sector of the valid Sega CD test BIN image, and going to "press start button". Once doing so, it reads the same first sector again, and then hangs forever. From the top ... The CDD seeks to sector 145 (-5 if you will), skips writing sector 145 due to DE...
by byuu
Wed May 22, 2019 2:53 pm
Forum: Mega/SegaCD
Topic: Questions on writing a new Mega CD emulator
Replies: 114
Views: 34861

Re: Questions on writing a new Mega CD emulator

According to the microcontroller sourcecode, the status is returned with 'not ready (0xf) report code until the TOC is fully read in lead-in area and the drive is paused outside lead-in area. Okay, cool. Can do then. I found some websites that mentioned the lead-in area is 7500 sectors, and I guess...