Genesis/Mega Drive rebuild project

For hardware talk only (please avoid ROM dumper stuff)
uprock7
Interested
Posts: 10
Joined: Wed May 01, 2013 6:20 pm
Location: United States

Genesis/Mega Drive rebuild project

Post by uprock7 » Thu May 02, 2013 5:39 pm

I was recently inspired by low_budget's super 8 NES rebuild project and Id like to rebuild a genesis myself. After spending time doing research over the last few weeks, I believe I would have to base my design off V0/V1/V2 model 1 designs because I dont believe I can source any of the ASIC's sega used in later board revisions. I have a computer science degree and enjoyed circuits classes and labs, so I think this would be a fun little project for me.

For the first version of the rebuild my main goals are to achieve perfect game compatibility, clear full stereo sound with the YM2612, cxa1645 s-video out, redesign of the power circuits, compatibility with 32x, sega cd, and sms power base.

Other than sourcing out obsolete IC's are there any other difficulties you guys might foresee?

djcouchycouch
Very interested
Posts: 696
Joined: Sat Feb 18, 2012 2:44 am

Post by djcouchycouch » Fri May 03, 2013 1:06 am

Are you looking to make a production of it or just the one?

Not knowing anything about electronics, how about HDMI instead of s-video?

uprock7
Interested
Posts: 10
Joined: Wed May 01, 2013 6:20 pm
Location: United States

Post by uprock7 » Fri May 03, 2013 3:20 pm

for the first build id rather stick to just composite/svideo out. im not entirely familiar with the genesis VDP or HDMI encoding IC's to really make it happen right now. if anything, id like to add a SD card slot for loading software. maybe on a v2 or v3 HDMI might be a possibility. But getting the first version working is the first step.

im also not concerning myself about building consoles for other people right now. depending on how difficult it is to acquire IC's and putting everything together, it might not be realistic to sell them to others.

Anyone know anywhere I could purchase the VDP, bus arbiter, and I/O IC's?

inu
Very interested
Posts: 50
Joined: Thu May 09, 2013 10:12 am

Post by inu » Thu May 09, 2013 12:17 pm

Don't forget the SCART connector for RGB, it would be a shame to waste the better signal that Sega console can create, and those connectors are pretty cheap anyway. Even tho simply not having to connect a cable from the Sega Genesis to the 32X alone will help somewhat.

You can still sell the boards even if you can't find a way to get all the ICs, just make sure people understand they'll need parts from an actual console.
The idea of consolidating all 3 consoles is too tempting, it would save lots of space (mess) for starters, and could help the CD32X homebrew development, plus things like easy an replace fuses, internal universal power supply, and not having to worry about old non-solid leaking capacitors will also make people want to jump to a potential replacement board.

Funny tho, I just made a huge comment about making a new board in another thread, and right under there was this one with you already working on something similar. :P

Edit 1:
The only big issue I can think of, is that including the Sega CD BIOS would not be legal\possible, but it can be worked around by building a new custom one or have people flash it themselves later.

(Edit 2 - Stuff uprock7 probably already knows but other people mind find interesting)
At least the Motorola MC68HC001CFN8, Yamaha YM 2612 and Zilog Z84C0006FEC from the Mega Drive and the Motorola MC68HC001CFN12 from the Mega CD\Sega CD seem to pop quite often with not much googling, they should be cheap and easy to acquire, which should make it a decently easy start. And there is at least 1 MD\Genesis FPGA project... if they were properly implemented there... could fix the issue with finding the SEGA ASICs for the basic console...

The Sega CD [SEGA 315-5632] pops few websites but they don't have a whole lot of units left in stock it seems.
(Not sure how reliable some of these websites are, just posting them as a curiosity mostly)
http://www.digipart.com/part/315-5632
http://www.iso-group.com/Public/Search_ ... 9149615C73
http://www.newyorksemi.com/index_part_en_315-5632.phtml

...and the Sega Mega Drive's VDP [Sega 315-5313]...
http://www.newyorksemi.com/index_part_e ... A-01.phtml

uprock7
Interested
Posts: 10
Joined: Wed May 01, 2013 6:20 pm
Location: United States

Post by uprock7 » Tue May 14, 2013 7:54 pm

oh man, thanks for the link to new york semi. i couldnt find the VDP or the Bus arbitrator and I/O ics and i was afraid i would have to emulate them using a microcontroller.

the sega cd bios has been somewhat reverse engineered, i believe? it would be awesome to build in sega cd, but im not going to worry about it right now.

inu
Very interested
Posts: 50
Joined: Thu May 09, 2013 10:12 am

Post by inu » Wed May 15, 2013 6:28 am

uprock7 wrote:oh man, thanks for the link to new york semi. i couldnt find the VDP or the Bus arbitrator and I/O ics and i was afraid i would have to emulate them using a microcontroller.

the sega cd bios has been somewhat reverse engineered, i believe? it would be awesome to build in sega cd, but im not going to worry about it right now.
Glad to help, and good thing there are still bits of stock all over the place.

Think it has been decompiled, but no one bothered (yet, and to my knowledge) to actually create a new universal region-free BIOS, striped of stuff like Sega logos\images\references. Guess I'll dig a bit into that when I have the time.

The reason for so many 3in1 system references is simply because it sounds more appealing as every Mega Drive model is still very easy to find in auction websites. However I do admit, that would still leave 1 problem to solve; the actual CD drive that would have to be taken from a Mega CD II.
Read that the Saturn CD drive might be compatible, but might just be another internet rumor.
It was also what made me end up in this thread. I've been looking for a community custom-made, better thought out system, with more convenient connectors (like SCART instead of silly DIN or miniDIN) for some time now.
Not only that, the add-on attachments (both 32X and SCD) are getting quite expensive around these parts.

That being said I'm actually very curious about how the project is gonna turn out, a custom made feature "perfect" region free system still has quite some appeal to it.
Please keep us posted of any development.

djcouchycouch
Very interested
Posts: 696
Joined: Sat Feb 18, 2012 2:44 am

Post by djcouchycouch » Wed May 15, 2013 1:19 pm

Reading the above, a couple of somewhat related questions came to mind:

- I'm actually surprised one can buy VDP chips! They're still being manufactured by someone? Or they're left over stock from way back when they were being manufactured?

- I imagine there's an increasing difficulty in finding reliably working Sega CDs. Would it be possible to bypass the whole problem by creating a device that plugs into the Sega CD connector of the Genesis but reads ISO files from USB sticks/SDCards/External Harddrive? Kinda like an Everdrive Sega CD. What would be the difficulty in making that?

inu
Very interested
Posts: 50
Joined: Thu May 09, 2013 10:12 am

Post by inu » Wed May 15, 2013 2:19 pm

djcouchycouch wrote:Reading the above, a couple of somewhat related questions came to mind:

- I'm actually surprised one can buy VDP chips! They're still being manufactured by someone? Or they're left over stock from way back when they were being manufactured?

- I imagine there's an increasing difficulty in finding reliably working Sega CDs. Would it be possible to bypass the whole problem by creating a device that plugs into the Sega CD connector of the Genesis but reads ISO files from USB sticks/SDCards/External Harddrive? Kinda like an Everdrive Sega CD. What would be the difficulty in making that?
1- Likely just left over stock. But correct me if I'm wrong.

2- It's not easy; this is a Computer Engineer department, but a prototype for the Dreamcast has already been created before, so the short answer is "It's perfectly possible". Just Google "GD-ROM drive emulator".
SDHC would be the medium chosen, It would be far more complicated to do it with a USB compatibility.
I can also tell you it would not be cheap, the drive replacement price will likely be between $50 and $150. If uprock7 or someone else ever decides to create the mentioned 3in1 I'm sure someone (maybe krikzz since he already created the Mega Everdrive) will eventually step up and finish the "perfect Mega Drive CD32X".
Some people might say you need to use the actual disc to get the best experience, but I rather keep them in the case to avoid any kind of accidental damage.

uprock7
Interested
Posts: 10
Joined: Wed May 01, 2013 6:20 pm
Location: United States

Post by uprock7 » Wed May 15, 2013 3:09 pm

i just bought some of the VDP's and the 315-5402's last night :p. id love to build a 3 in 1, but first things first, rebuild the genesis and see what improvements i can make.

im thinking:
100% game and accessory compatibility
crystal clear stereo sound from the YM2612
US/JAP switch
replace the sony cxa1145 with a cxa1645
add composite, svideo, scart hookups

then from there:
reading games from SD card
HDMI out
bluetooth controller support

and then:
ultimate 3 in 1 integration of sega cd and 32x.

i bet ill be able to get the first round of improvements working, but who knows from there :)

inu
Very interested
Posts: 50
Joined: Thu May 09, 2013 10:12 am

Post by inu » Wed May 15, 2013 3:38 pm

Just got to say I like your plan!

Don't forget an EU and 50Hz switch. Some PAL editions of games, like Alien Soldier, run at full speed in 50Hz, and most of the others just don't like to jump regions.

Edit:
Well, think you might not have to worry so much with the Bluetooth controller.
http://www.joystiq.com/2013/05/15/retro ... o-conoles/

Something else came to mind that you might be able to fix on the rebuild if you're feeling unchallenged. :P
I'm no Master System fan (or have much interest in that system in particular) or ever owned a Power Base Converter, but compatibility with that console had 3 "issues".
1 - It's annoying that the PAUSE button is on the console instead of the controller. It might be an inherited console design fault, on how the system is halted or something, but it's probably worth a quick check just to see how much would need to be changed to make it work from the controller.
2 - Not all games are compatible with the MD\Genesis controllers. You're required use a Master System controller for those.
3 - You can't plug the Converter on top of the 32X (duh!), but it would be technically possible to add an extra slot to your unit and simply bypass all this mess if you're looking to increase the value of your design.
I'm aware this last one would be easier to fix when the 32X is integrated, and the cartridge slots are replaced by SD card sorcery, but I still felt like pointing it out.

uprock7
Interested
Posts: 10
Joined: Wed May 01, 2013 6:20 pm
Location: United States

Post by uprock7 » Sun May 19, 2013 5:22 am

1 - It's annoying that the PAUSE button is on the console instead of the controller. It might be an inherited console design fault, on how the system is halted or something, but it's probably worth a quick check just to see how much would need to be changed to make it work from the controller.
2 - Not all games are compatible with the MD\Genesis controllers. You're required use a Master System controller for those.
3 - You can't plug the Converter on top of the 32X (duh!), but it would be technically possible to add an extra slot to your unit and simply bypass all this mess if you're looking to increase the value of your design.
adding a second slot for master system and integrating the power base into the system doesnt seem difficult. it would be possible to add some micro controller to pass controller signals normally if a genesis game is loaded and to fix controller compatibility for sms games and map a button like 'start' to pause. im thinking id have to add a microcontroller anyway for SD card support, maybe it could do double duty and manage controllers as well.

does anyone know where to get the oscillators for genesis? the 53.634165Mhz one and the 53.203424Mhz one?

TmEE co.(TM)
Very interested
Posts: 2406
Joined: Tue Dec 05, 2006 1:37 pm
Location: Estonia, Rapla City
Contact:

Post by TmEE co.(TM) » Sun May 19, 2013 1:01 pm

Use a PLL and 3.579545 and 4.433619MHz crystals
Mida sa loed ? Nagunii aru ei saa ;)
http://www.tmeeco.eu
Files of all broken links and images of mine are found here : http://www.tmeeco.eu/FileDen

inu
Very interested
Posts: 50
Joined: Thu May 09, 2013 10:12 am

Post by inu » Sun May 19, 2013 4:01 pm

Those seem kind of harder to find around these parts (after a small search).

http://www.syntax.com.tw/products/produ ... temid=6622
http://www.syntax.com.tw/products/produ ... temid=6623

These are from TXC and everything, but making such a small order from Taiwan kind of blows.

TmEE alternative is likely cheaper.

Well, if you're gonna go for SD card, the extra cartridge slot for Master System is starting to sound a bit silly again. At least that way even the games in card format would work. :P
Last edited by inu on Mon May 20, 2013 5:35 pm, edited 2 times in total.

uprock7
Interested
Posts: 10
Joined: Wed May 01, 2013 6:20 pm
Location: United States

Post by uprock7 » Mon May 20, 2013 3:40 pm

i feel like there is a nice aesthetic around plugging in a game and just playing. now i put a game in my ps3/xbox360, navigate and tell the console to play the game, then it connects to check for updates, installs updates if applicable, and then i get to play the game. ill probably have a board revision with a secondary master system slot just to see if people are interested.

Thanks TmEE for point out those alternate oscillators. it never occurred to just use any off the shelf NTSC and PAL oscillators.

speaking of oscillators, id like to add a turbo button to overclock the cpu on the genesis to smooth out game play and eliminate slow down and sprite flickering.

i also wonder how hard it would be to integrate a save RAM cart into the board for people with sega cd game saves.

inu
Very interested
Posts: 50
Joined: Thu May 09, 2013 10:12 am

Post by inu » Tue May 21, 2013 1:02 am

Stuff is starting to pile up.

US\JP\EU selector (or rather, JAPANESE <-> ENGLISH selector, I keep confusing this part and saying nonsense about it, my bad)
50Hz\60Hz selector
Overclock for the Motorola 68000 (on\off?); which will add another think to be careful about since the 32X won't work if the 68000 it's overclocked.
SD card game listing

It's starting to sound like a nice, simple menu would come in handy, instead of adding a dip switch under the device or something; when u get all the basics working.
Or just go all out and come up with a really neat menu like in the 64drive.

Since you're gonna implement the SD card and will have some spare logic... it would make sense to have the RAM cartridge.
There doesn't seem to be much inside those ( http://nfggames.com/forum2/index.php?topic=3383.0 ), and the Mega Everdrive includes this function as well.

There was also a post somewhere about someone overcloking the SH-2's on a 32X (that had TmEE sharing his negative experience with it I think), which lead to a much smoother frame rate in 3D games since we're mentioning overclocking.

Btw, are you planing on keeping the Serial port too?

Post Reply