Sega Channel

bluelight · Post by **bluelight** » Fri Feb 27, 2009 4:01 am

Does anyone have an existing bios for sega channel.

I am looking to get the menu selection available. Even with out graphics.

So far I've come close to is the adaption connection menu.. Been able to hex edit that a little bit.

Curious if anyone has a private bin or bios.

Nemesis · Post by **Nemesis** » Fri Feb 27, 2009 4:08 am

Yeah, I've dumped the bios files from my Sega Channel units. I'll upload them when I get home in a few hours.

Nemesis · Post by **Nemesis** » Fri Feb 27, 2009 7:10 am

Ok, here's the bios from the big "General Instrument" Sega Channel:
http://nemesis.hacking-cult.org/MegaDri ... l%20GI.zip

That's the only dump I have saved. I have the other "Scientific Atlanta" Sega Channel adapter, but the bios for that matched the ROM already in the goodgen set IIRC.

bluelight · Post by **bluelight** » Fri Feb 27, 2009 6:30 pm

Awesome, Nemesis! Thank you a lot..

I am going to working on some ASM/Hex editing. See what I can come up with. If things progress, or go well. I will post my findings and credit to you!

Okay, that is great. I'll take a look at goodgen set, if decide to modify the "Scientific Atlanta" version as well.

Sincerely!!

bluelight · Post by **bluelight** » Thu Jun 04, 2009 3:07 am

I got ahold of both the SA and GI adapters. And have been hexing and disassembly the bin. Unfortunately even SEGATool finds some of the assembly structures to be unrecognized.

Maybe I could attempt a rom dump to one of the units.
Do you remembers if this binary contains the menus, as well...

The original RAM originally contains something around 32MBs.

Nemesis · Post by **Nemesis** » Mon Jun 15, 2009 6:07 am

The BIOS I've uploaded is the complete BIOS for the unit. I always overdump to 32Mbit on peripherals like this to make sure of that.

The Sega Channel is quite a complex device. The BIOS itself is going to be attempting to communicate with other hardware present in the physical cart, and that hardware doesn't exist when you try and run that ROM in an emulator. If you want to get this BIOS to do much of anything, you're going to need to "fake out" the BIOS into believing the rest of the hardware is present and working correctly. For some devices this is quite easy (eg, as in the case of Virtua Racing), but from what I've seen of the Sega Channel BIOS, it's a lot more challenging. It can certainly be done, and often it doesn't take very much in the end to get something like this working, but you are going to need a good understanding of assembly programming on Mega Drive hardware to identify where things are getting caught up, and what you need to do to get the BIOS to move past these points. If you want help with this, you might have more luck asking for help on a site more oriented around hacking games for the Mega Drive, like the Sonic Retro forums at http://forums.sonicretro.org.

powerofrecall · Post by **powerofrecall** » Tue Jul 07, 2009 1:29 am

Haven't posted here in a bit... I actually started an IDA disassembly of this but lost interest, if anyone wants my idb file I could put it up somewhere. It does indeed make calls to onboard hardware, but I'm sure these could be nop-ed out or jumped over to make it do some stuff. My understanding though is there is hardly anything contained in the ROM itself--the disassembly has seemingly little non-code stuff in it.

bluelight · Post by **bluelight** » Fri Sep 25, 2009 7:00 pm

Nice! I was having difficulty getting the IDA disassembly to work properly.

I'd be interested in looking at your idb file. Sendit or post a link.

powerofrecall wrote:Haven't posted here in a bit... I actually started an IDA disassembly of this but lost interest, if anyone wants my idb file I could put it up somewhere. It does indeed make calls to onboard hardware, but I'm sure these could be nop-ed out or jumped over to make it do some stuff. My understanding though is there is hardly anything contained in the ROM itself--the disassembly has seemingly little non-code stuff in it.

My understandings also showed there was little contained in the ROM itself. Letting me believe, it may be possible the menu graphics or any sprites were not contained in this dump. However, its complete data structure is unclear to me.

LocalH · Post by **LocalH** » Sat Nov 28, 2009 9:11 pm

Recently a Sega Channel "Demo Cartridge" (#4 apparently) was sold on eBay. The buyer sent me the cart and I have dumped it.

Sega Channel Demo Cartridge #4 (2-16-94)

Eke · Post by **Eke** » Sun Nov 29, 2009 1:30 pm

Very nice demo, thank for the dump !

powerofrecall · Post by **powerofrecall** » Sun Dec 13, 2009 3:24 pm

Man, stuff like this is why I keep coming here. Awesome

I haven't done any more disassembling of the SC firmware because I kind of just lost interest in it. It's sad that it really is a totally lost, worthless piece of hardware now--so there's hardly any point in documenting it.

edit: Plus, this ROM kind of acts to preserve some of it anyway--LocalH I assume there were more of these if they were numbered?

King Of Chaos · Post by **King Of Chaos** » Sun Dec 13, 2009 5:29 pm

If I remember right, there was another Sega Channel beta cart on eBay not too long ago.

bluelight · Post by **bluelight** » Wed Dec 16, 2009 6:01 am

Thank you so much--Nemisis, powerofrecall, and ofcourse LocalH!!!

GREAT JOB.

LocalH · Post by **LocalH** » Wed Dec 16, 2009 8:15 pm

King Of Chaos wrote:If I remember right, there was another Sega Channel beta cart on eBay not too long ago.

I think it was cart #6. I saw a scan of it, and it had the same date, thus I think it's the same build (Sega probably gang-wrote them for various demonstration and testing purposes).